NSW Stage 5 sample module

SCI EN CE

S tage

Melinda Mestre

Lily Okati

Timothy Sloane

Mora Soliman

Helen Silvester

NSW Curriculum

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1.7

2.5

2.6

2.7

2.8

2.9

3.1

3.4

3.5

3.6

3.7

3.8

3.9

Module 4 Disease

4.1

4.5 The immune system protects us from infectious

4.6 Investigation: Modelling the spread of

4.7 Minimising the impact of infectious and non-infectious diseases

4.8 Immunisation programs and the occurrence of

4.9 Using stem cells to restore damage to the retina

4.10

Module 5

5.1

5.3

5.4 Investigation: Products produced from Australian minerals and resources

5.5 Aboriginal and Torres Strait Islander Peoples use minerals and resources

5.6 Extracting resources affects the environment

5.7 Investigation: The environmental impact of

5.8

6.1

6.2 Ions

6.3 Investigation: Modelling the formation of cations and anions

6.4 Metal cations and non-metal anions

6.5

6.6

6.7

6.8

6.9

6.10

6.11 Polymers

6.12 Investigation:

6.13

6.14

6.15

6.16

7.1 Sustainability

7.2

7.3

7.4

7.5

7.6 Investigation: The relationship between industrialisation and the rise in global

7.7 Investigation: Trends and insights from climate data ...........................................................................................275

7.8 Science in context: Humans can reduce greenhouse

7.9 Challenge: Measuring carbon stored in trees

7.10 The effects of climate change

7.11 Challenge:

7.12 Effects of climate change

7.13 Investigation:

7.14

7.15 Pollution

7.16 Aboriginal and Torres Strait Islander Peoples have

7.18 Investigation: How scientists develop ways

7.19

in context: Human activity and environmental

7.20 Investigation: What does the data collected by satellites tell us?

7.21

8.1

8.2

8.3

8.4

8.5

8.6

8.7 Meiosis

8.8

8.9

8.10

8.11

8.12

8.14

8.15

8.16

8.17

8.18

8.19

8.20

8.21

8.22

8.23

Module 9

9.1

9.2

9.3

9.4 Investigation: Divergent and convergent evolution of big beaks and small beaks

9.5 Fossils provide evidence of

9.6 Investigation: Popcorn

9.7 Multiple forms of evidence

9.8 DNA and proteins provide chemical evidence for

9.9 Investigation: Who is my cousin?

9.10 Aboriginal and Torres Strait Islander Peoples' artwork

9.11

Module 10 Chemical reactions

10.5

10.7 Investigation:

10.8

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Module 12 Waves

12.1

12.3

12.4

12.5

12.6

12.7

12.8

12.10

12.12

12.13

12.14

12.15

13.1

13.5

13.7

13.8

13.9

13.10

13.11

13.12

14.1

14.5

14.7

Introducing Oxford Science Stage 5 NSW Curriculum

Congratulations on choosing Oxford Science Stage 5 NSW Curriculum as part of your studies this year!

Oxford Science Stage 4 NSW Curriculum has been purpose-written to meet the requirements of the Science 7–10 Syllabus (2023). It includes a range of flexible print and digital products to suit your school and incorporates a wide variety of features designed to make learning fun, purposeful and accessible to all students!

Key features of Student Books

The Working scientifically is a standalone module that explicitly teaches important Science inquiry skills.

The Aboriginal and Torres Strait Islander Histories and Cultures cross-curriculum priority is addressed in both standalone lessons and within other lessons.

In each core lesson:

• a concept statement summarises the key concept in one sentence key ideas are summarised in succinct dot points

• key terms are bolded in blue text, with a glossary definition provided in the margin a set of check your learning questions are aligned to the learning intentions for the lesson.

Science in context lessons explore real world examples and case studies, allowing students to apply science understanding.

The Test your skills and capabilities section provides scaffolded opportunities for students to apply their science understanding while developing skills and capabilities.

DRAFT

For a complete overview of all the features and benefits of this Student Book:

Practical activities appear within each module, directly after the core lesson they relate to. Additional activities are provided through Oxford Digital.

Challenges, Skills labs and Investigations provide students with opportunities to use problem-solving and critical thinking, and apply science inquiry skills.

> activate your digital access (using the instructions on the inside front cover of this book) and click on “Introducing Oxford Science Stage 5 NSW Curriculum” in the Course menu.

Key features of

Oxford Digital has been designed in consultation with Australian teachers for Australian classrooms. The new platform delivers fully accessible, reflowable course content with videos, autoand teacher-marked activities, interactives and more embedded right where you need them. There’s also a range of unique features designed to improve learning outcomes.

DRAFT

As a student, you can:

> view all Student Book content in a fully accessible, reflowable format that’s delivered in bite-sized chunks so you can work at your own pace

> use the “Read to me” button to have any part of the course read aloud to you

> highlight, take notes, bookmark pages , or define words with the built-in Australian Oxford Dictionary

> watch hundreds of concise key content videos to help you revise anything you don’t understand, catch up on things you’ve missed or help you with your homework

> complete hundreds of interactive questions and quizzes as you work through the content and get the answers and results sent to you.

x  Oxford Science Stage 5 NSW Curriculum Oxford University Press

As a teacher, you can:

> elevate your teaching and reduce planning and preparation time with Live Lesson mode. This is an Australian first that lets you upgrade from traditional print-based lesson plans to fully interactive, perfectly sequenced and timed interactive lessons complete with classroom activities that are ready to go

> personalise learning for every student and differentiate content based on student strengths and weaknesses. Assign support or extension resources to any student using a range of differentiation resources

> begin every lesson with ready-made learning intentions and success criteria

> revolutionise your planning, marking and reporting with powerful analytics on student performance and progress.

DRAFT

• Assessment report shows how students are performing in each online interactive assessment, providing feedback for teachers about areas of understanding

• Curriculum report summarises student performance against specific curriculum content descriptors and curriculum codes

For a complete overview of all the features and benefits of Oxford Digital:

> activate your digital access (using the instructions on the inside front cover of this book) and click on “Introducing Oxford Science Stage 5 NSW Curriculum ” in the Course menu.

Meet the authors & reviewers

Melinda Mestre

Author

Melinda is currently the Head of Science in the independent school’s sector. She has a Master of Educational Leadership (with Excellence) and holds degrees in science, chemistry and education. Melinda is also employed by various educational organisations and universities in a variety of roles including a unit convenor and sessional academic, teaching units relating to secondary education and science. Melinda sits on the Science Professional Learning Advisory Committee with the AIS, presenting at various science workshops throughout the last several years. Melinda is a passionate educator who is driven by supporting teachers in their understanding of how to teach science to promote student academic growth.

Lily Okati

Author

Lily Okati has over a decade of experience teaching science, physics, and chemistry across Stages 4–6. She holds a Bachelor of Science, a Master of Physical Chemistry and a Master of Education. In addition to her classroom teaching, she has contributed to the development of physics trial examination papers for the Catholic Secondary Schools Association. Her professional interests lie in curriculum development and fostering deep scientific understanding among secondary students.

Timothy Sloane

Author

Timothy Sloane is the Head Teacher of Science at Concord High School, with over 20 years of experience teaching HSC biology in NSW schools. Before teaching, he was a published research scientist in cardiovascular disease. He holds a Master of Education, focusing on ICT in science education to boost student engagement.

His profile within the science teaching community and expert knowledge of assessment, curriculum content and best practice delivery of that content has led to multiple high-profile leadership and resource development opportunities within the profession. He has presented at numerous conferences and workshops, including HSC Meet the Markers, the BEEST conference and the Centre for Professional Learning, where he has shared his expertise in syllabus programming, and the development of Stage 4 and 5 student research projects, and Stage 6 depth studies and associated marking criteria. Timothy has a keen interest in improving students’ scientific literacy, focused on the use of A.L.A.R.M (A Learning and Responding Matrix) to enhance students’ writing.

Additionally, he has conducted HSC student study workshops at UNSW, USYD and local community libraries, demonstrating his commitment to enhancing student learning and professional development in education.

Mora Soliman

Author

Mora completed a Bachelor of Technology in Biotechnology as her undergraduate degree and was a microbiologist before completing a Graduate Diploma in Education and starting her teaching career in 2003. She completed a Master of Education Leadership in School Education in 2013 and has been working in independent and Catholic schools in NSW over the last 20 years. She is currently Head of Science at St Vincents College in Ashfield and has taught chemistry, biology and physics for both the old syllabus and current syllabus. She is currently teaching chemistry and Science Extension. She has been a committee member and presenter for Association of Independent Schools and Science Teachers Association NSW. She has also been on exam committees for chemistry and Science Extension and has been a senior HSC marker for both chemistry and Science Extension. She worked with Oxford University Press on the Skills and Activity Book for the previous edition and is an author of the Data Science modules in this new edition.

Helen Silvester

Author

Helen Silvester is a neuroscientist by training and an experienced science educator with a passion for fostering scientific understanding. With over 20 years of experience in education, she has taught science to students ranging in age from 3 to 18 years. Helen is dedicated to science communication in all its forms, including teaching, presenting, curriculum design and textbook writing. She draws on her extensive experience and current research to develop innovative curriculum resources for both students and educators. Helen currently serves as the Learning Area Manager (Science) at the Australian Academy of Science, where she leads the development of the Primary Connections and Science Connections resources.

Jarrah Cain First Nations reviewer

DRAFT

Jarrah is a proud Aboriginal woman who descends from the Gomeroi and Darkinyung nations. She is passionate about science and believes that through a culturally inclusive environment, we can learn best practices in environmental sustainability and management. Jarrah is a teacher inspired by her culture and connection to Country. She strongly believes that through sharing, advocating and leading Aboriginal education, we can make a difference and pave a path to a reconciled Australia. Jarrah is the recipient of the Deadly Science STEM Teacher Award for 2024 and is a role model for other Aboriginal women and girls who want to embrace a career in education and science.

Overview

Module 2

Energy DRAFT

The law of conservation of energy states that energy is always conserved during transfers and transformations, meaning the total energy stays the same. Not all energy transfers are 100% efficient, however, and some energy is wasted as heat or sound. A Sankey diagram shows how energy is transferred and transformed. We can use our understanding of energy efficiency to examine Aboriginal and Torres Strait Islander ground ovens. We will also compare different sources of energy which are used to generate electricity, such as coal, hydropower and solar.

Lessons in this module

Lesson 2.1 Energy cannot be created or destroyed (page 58)

Lesson 2.2 Sankey diagrams can represent energy efficiency (page 62)

DRAFT

Lesson 2.3 Investigation: What if you bounced a ball? (page 65)

Lesson 2.4 Electricity can flow through circuits (page 66)

Lesson 2.5 Skills lab: Understanding resistor colour codes (page 71)

Lesson 2.6 Investigation: Demonstrating electrostatic electricity (page 72)

Lesson 2.7 Current can flow through series and parallel circuits (page 73)

Lesson 2.8 Investigation: Making series and parallel circuits (page 77)

Lesson 2.9 Voltage, current and resistance (page 77)

Lesson 2.10 Investigation: Investigating Ohm’s law (page 82)

Lesson 2.11 How is power measured? (page 83)

Lesson 2.12 Investigation: Comparing the energy transformed over time (page 85)

Lesson 2.13 Energy efficiency can reduce energy consumption (page 87)

Lesson 2.14 Challenge: Design an energy-efficient house (page 90)

Lesson 2.15 Electricity is generated from different energy sources (page 92)

Lesson 2.16 Solar cells transform the Sun’s light energy into electrical energy (page 96)

Lesson 2.17 Review: Energy (page 101)

Energy efficiency

If a device transforms most of its input energy into the most useful output energy, like a trampoline, then it is considered to be a very energy-efficient device. Energy is said to be “wasted” if it is in a form that cannot be used, such as heat or sound. The less “wasted energy”, the more energy-efficient the device. Energy efficiency is a measure of the percentage of useful energy transformed.

Theoretically, the total amount of energy is constant when you jump on a trampoline. In reality, there may be a small amount of heat energy produced as you fall due to air resistance. This “loss” of energy is not really a loss but rather just a transformation of energy to a nonusable form. The efficiency can be calculated by comparing how high above the trampoline you started and the height you reached on the rebound (usable f inal energy). Any difference in height is a result of heat or sound energy.

Efficiency (%) = useful energy output energy input × 100

Take the trampoline example in Figure 2. The input energy was 500 joules (J) and the useful output energy was 400 J. This means that the trampoline is 400 ÷ 500 × 100 = 80% efficient

500 joules elastic energy

400 joules gravitational potential energy

energy efficiency a measure of how much input energy is transformed, rather than lost (via sound or heat)

DRAFT

joule (j) the unit of energy; its symbol is J

Most energy transformations for everyday appliances aren’t as efficient as trampolines. Scientists are constantly trying to design the best appliances possible with the highest efficiency ratings. This would make them better for the environment and cost less to power. Do you and your family always buy the most efficient appliances? Are you familiar with the star ratings on appliances? More stars mean that the appliance is more energy efficient. Not only is it good to know that less energy is being wasted, but it also means that when you pay your electricity and gas bills you are paying for energy that is being used rather than for energy that is being wasted.

Worked example 2.1A shows how to calculate energy efficiency.

Worked example 2.1A Calculating energy efficiency

Calculate the efficiency of a device if its input energy is 150 J and its waste energy is 60 J.

Solution

Steps What to do

Working out

a. Calculate the component of useful energy. Useful energy = input energy − waste energy = 150 − 60 = 90 J

b. Calculate the energy efficiency by substituting the values into the formula. Efficiency (%) = useful energy output energy input × 100 = 90 150 × 100 = 60%

c. State the efficiency of the device. The device has an energy efficiency of 60 per cent.

DRAFT

Heat and sound waste energy

If no system is 100 per cent efficient, but the energy cannot be destroyed, then where does the energy go? In most cases, the energy is transformed into heat and sound energy. Think what happens when we drop a ball on the ground. The ball starts with gravitational potential energy which is transformed into kinetic energy when we drop it. When the ball hits the ground, it makes a noise. The louder the noise, the more sound energy it generates. If we bounce a ball many times in a row, we might feel the ball warm up. Heat energy has been generated. Both the heat and sound energy disperse into the air. They are not lost or destroyed. We cannot reuse them. They are by-products of the main energy transformation.

Pendulums

A pendulum is a mass that is attached by a string to a pivot point. When the mass is drawn upwards, it gains gravitational potential energy. When the mass is let go, the force of gravity pulls it back to its original position, converting the gravitational potential energy to kinetic energy. The momentum built up by the moving mass causes the mass to then swing in the opposite direction. This means all the kinetic energy is converted back into gravitational potential energy. Pendulums (like a swing in a playground) are a good example of how energy efficiency can be measured. Some kinetic energy is always lost as waste energy when it is transformed to heat and sound. This is evident when the pendulum does not quite reach the height at which it started.

5 A swing will not reach its original height because it loses energy as heat and sound energy.

Check your learning 2.1

Check your learning 2.1

Retrieve

1 Recall the law of conservation of energy.

2 Define “energy efficiency”.

Comprehend

3 Give an example of a closed system in everyday life and explain why it fits this definition.

4 Explain what it means if a machine is 80 per cent energy efficient.

5 Determine why a pendulum eventually stops swinging if no energy is added.

Analyse

6 Explain why a rubber band that had 10 units of elastic energy cannot produce 12 units of kinetic energy.

DRAFT

7 For the rubber band in question 4 , calculate its percentage efficiency if 7 units of kinetic energy were produced. Describe where the remaining 3 units of energy have gone.

8 Identify and describe the by-product energy transformations for a car.

Apply

9 “Energy was lost when I bounced a ball.” Do you agree or disagree? Think about the types of energy the ball had before, during and after the bounce. Explain how the law of conservation of energy applies in this situation and whether energy has truly been lost.

Skills builder: Questioning and predicting

10 Turning a scientific question into a hypothesis helps to structure an investigation. You are presented with the research question: “What happens to the amount of stored energy as a rubber band is stretched?”

a Rewrite this question as a scientific question. (THINK: How can I make this measurable?)

b Identify the dependent variable and the independent variable in your question. (THINK: What am I measuring? What am I changing?)

c Develop a hypothesis for stretching a rubber band. (THINK: Have I included both variables? Have I included a potential result?)

Learning intentions and success criteria

Lesson 2.2

Sankey diagrams can represent energy efficiency

Key ideas

→ The conservation of energy can be represented in a Sankey diagram.

Drawing energy efficiency

Sankey diagram a flow chart that represents movement or change in resources, such as the transfer or transformation of energy

conductor a material or substance that electrons can flow through; the flow of electrons through a conductor is electrical current

DRAFT

A hair dryer has two basic components: a fan and a heating element. When plugged in and switched on, the fan motor spins and the heating element heats up. This means that a hair dryer converts electrical energy into thermal (heat) energy and kinetic energy. The air blown by the fan is directed over the heating element, passing the heat energy to the air which flows out of the hair dryer. Some hair dryers have different speed and heat settings that control the amount of electrical energy flowing to each part of the device. Processes such as these can be represented using a Sankey diagram

Sankey diagrams

A Sankey diagram is a type of flow diagram. Sankey diagrams are used to represent the efficiency of energy transfers and transformations. The diagram visually demonstrates how energy moves through a system, whether it is transferred from one object to another or transformed from one form to another. Each Sankey diagram has a series of arrows of different widths. The widths of the arrows represent the amount of energy that flows in and out of a system.

Let’s look at the transfer and transformation of energy in toasters. Toasters use heating elements to convert electrical energy into thermal energy. Heating elements are made of wires that heat up without melting when electricity flows through them. These wires are poor conductors of electricity. If the wires resist the flow of charged particles and make it more difficult to move, then more electrical energy is transformed into thermal energy. The thermal energy is then passed to the air, which then passes the heat to the bread, toasting it. This transfer of energy can be represented in a Sankey diagram (Figure 1).

Drawing a Sankey diagram

The toaster gets hot, Useful work Heating the surroundings turning the bread into toast.

Electrical energy put in

Sankey diagrams have three main parts: the input energy, the output energy and the waste energy. The input energy is shown at the start of the arrow on the left-hand side of the diagram. The useful output energy is shown with an arrowhead travelling straight on to the right-hand side. The waste energy is usually shown by another arrowhead, travelling either

up or down on the diagram. Sankey diagrams are usually drawn on graph paper so that the width of the arrow can accurately represent the amount of energy (Figure 2).

Sankey diagrams are also used to represent complex energy transitions.

Worked example 2.2A shows the process of drawing a Sankey diagram.

Input energy (from the left)

Width of the arrow represents the amount of energy

Waste energy (vertically up or down)

Worked example 2.2A Drawing a Sankey diagram

Useful output energy (to the right)

Length of the arrow has no significance

A kettle has an input of 800 J of electrical energy. Heating the water uses 600 J of thermal energy while 200 J of thermal energy heats the surrounding air. Draw a Sankey diagram to represent this energy transfer.

Solution

Steps

What to do

a. Before starting your diagram, you will need to decide on a scale for the graph paper. It is usually easiest for one square to equal a simple number. In this case, one square = 100 J.

b. As the input energy is 800 J, this will be equal to eight squares down on the graph paper. Colour across a number of squares. Add a label to show the input energy.

DRAFT

c. The useful thermal energy that heats the water is 600 J. To show this, colour six squares down the graph paper from the top right of your input energy block. Colour across until you reach a few squares from the right edge of the graph paper. Add an arrowhead to the right side and a label to show the output energy.

Working out

Steps What to do

d. The waste energy (heating of the surrounding air) is 200 J. To show this, draw a block, two squares wide, extending down from the right of the input energy block. Add an arrowhead and label to show the waste energy. This is now a Sankey diagram of the energy input and output of the kettle.

Working out

Check your learning 2.2

Check your learning 2.2

Retrieve

1 Identify the three key parts of a Sankey diagram.

Comprehend

2 Describe how a Sankey diagram can help identify energy losses in a system. Apply

3 Draw a Sankey diagram to represent the energy transfers and transformations of a rubber band that starts with 10 units of elastic energy and produces 6 units of kinetic energy and 4 units of waste heat.

4 Using a Sankey diagram, compare the energy efficiency of two appliances: a kettle and a microwave. The kettle uses 2,000 J and delivers 1,800 J of useful energy. The microwave uses 2,000 J and delivers 1,200 J of useful energy.

Analyse

DRAFT

5 The Sun provides 400 J of light energy to a plant. The plant uses the light to store 100 J of chemical energy. Calculate the amount of waste energy from this process.

6 A student claimed a fan heater was inefficient due to energy lost as sound.

a Explain why thermal energy and kinetic energy is considered “useful” in a fan heater.

b Use Figure 3 to calculate the amount of sound energy generated.

Figure 3 Sankey diagram for a fan heater

7 Calculate the amount of electrical energy required by the television in Figure 4.

Figure 4 Sankey diagram for a television

Lesson 2.3 Investigation: What if you bounced a ball?

Purpose

To investigate the energy efficiency of a bouncing ball Materials

• Tennis ball

• Metre ruler

• A selection of other types of balls

• Blu-Tack or masking tape

Procedure

1 Hold the tennis ball 1 metre above the ground next to the vertical ruler.

2 Drop the ball (do not throw it) on a hard surface.

3 Use the metre ruler to measure how high the ball bounces back. Be careful to avoid parallax error by ensuring your eye is level with the ball.

4 Determine the percentage energy efficiency by using the formula below: efficiency (%) = height of bounce starting height × 100 1

Inquiry

Choose one of the following questions to investigate.

• What if another ball was bounced on the same surface? (Does it have the same efficiency?)

DRAFT

• What if the same ball was bounced on a different surface? (Does it have the same efficiency?) Answer the following questions in relation to your inquiry.

1 Write a prediction or hypothesis for your inquiry.

2 Identify the (independent) variable that you will change from the first method.

3 Identify the (dependent) variable that you will measure and/or observe.

4 Identify two variables that you will need to control to ensure a fair test. Describe how you will control these variables.

5 Write down the method you will use to complete your investigation in your logbook.

6 Draw a table to record your results.

7 Show your teacher your planning for approval before starting your experiment.

Table 1 Bouncing ball experiment

Independent variable (surface/ball)

Height of bounce

Attempt 1

Attempt 2

Attempt 3

Results

1 Copy and complete Table 1.

2 Draw a column graph showing how the energy efficiency of the balls changed with your independent variable.

Discussion

1 Describe the results of your experiment by describing how you changed the independent variable and how this affected the dependent variable.

2 Compare (the similarities and differences between) the results of your experiment and your hypothesis.

Average height of bounce Efficiency (%)

3 Identify the type of energy the ball had: – before it was dropped – just before it hit the ground – as it touched the ground.

DRAFT

4 Identify the waste energy.

5 Draw a flow diagram of the energy transformation.

6 Draw a flow diagram of the energy transfer.

Conclusion

Describe how the independent variable affected the dependent variable.

Lesson

2.4

Electricity can flow through circuits

Key ideas

→ A closed circuit occurs when the positive and negative charges can be separated and reunited.

→ An electrical conductor allows the charges to flow easily.

→ An electrical insulator restricts the movement of the charges.

Introduction

“Electricity” is a general term related to the presence and flow of charged particles. An electric charge can be either positive or negative. It is produced by subatomic particles (parts of atoms), such as electrons, which carry a negative charge, or protons, which carry a positive charge.

Electrostatic charge

Objects are normally uncharged; that is, their atoms usually have equal numbers of positive protons and negative electrons. But when two objects are rubbed together, some of the electrons on the surface may be transferred from one object to the other. This causes the object with fewer electrons to become positively charged and the object with extra electrons to become negatively charged. This is called an electrostatic charge.

You can see examples of electrostatic charge when you rub a balloon against a woollen jumper and your hair stands up when you bring the balloon close to your head, or if you walk across a synthetic carpet and you get a small shock when you touch a door handle. In both these cases, the positive or negative electric charge stays on the charged object without moving. If the charges on two objects are the same (both positive or both negative), then they are described as “like charges”. If the charges are different (one positive and one negative), then they are described as “unlike charges”.

The following are important rules to learn about electrostatic charges (Figure 1).

• Like charges repel.

• Unlike charges attract.

• Charged objects attract neutral objects.

When charged objects are close to each other, the small negative electrons are attracted to the positively charged object (unlike charges attract). If these two objects are brought close enough, the electrons will try to jump across the gap as a spark. This is what happens when the air particles in a cloud rub against each other and become charged. If the charges build up enough, a large spark (lightning) will move between the charges in the clouds or towards the neutral ground (charged particles and neutral objects are attracted to each other).

The Van de Graaff generator is a machine that produces an electrostatic charge by rubbing a belt (Figure 2). The surface of the dome can lose electrons and become positively charged. Anything that touches the top of the dome also becomes positively charged. If a person touches the surface of the dome, their hair can become positively charged, causing the strands of hair to stand on end and move away from each other. This happens because the positive charges in the hair strands repel one another (like charges repel).

Similar generators are used to accelerate particles in X-ray machines and food sterilisers, and in nuclear physics demonstrations.

electric charge a property of subatomic particles (electrons and protons) that results in electric energy; electric charge can be positive or negative electron a negatively charged particle that moves around in the space outside the nucleus

proton a positively charged subatomic particle in the nucleus of an atom

electrostatic charge an electric charge between two objects caused by a deficiency or excess of electrons (negative charges)

de Graaff generator  a machine that produces an electrostatic charge

2 Placing a hand on the Van de Graaff generator causes negatively charged electrons to move from a person’s hair to the dome. The positive charges that are left in their hair strands cause the strands to repel each other.

wet cell contains wet substances and uses a chemical reaction to produce electrical energy (e.g. a car battery)

dry cell contains dry substances and uses a chemical reaction to produce electrical energy; commonly used for portable devices such as a torch battery

electric current the flow of electrical charge through a circuit

electric circuit a closed pathway that conducts electrons in the form of electrical energy conventional current the flow of positive charges in a circuit

Electrical potential energy and circuits

When positive and negative electric charges are separated, they gain electrical potential energy, much like how an object gains gravitational potential energy when lifted against gravity. If you drop the object, it moves from a higher gravitational potential energy to a lower point, and this difference in potential energy is converted into kinetic energy. Similarly, when electric charges move from a point with higher electrical potential energy to one with lower potential energy, the difference in electrical potential energy transforms into kinetic energy, causing them to move.

It is difficult to continually rub things together to separate charges and give them electrical potential energy. An energy source, such as a dry cell (e.g. a torch battery) or a wet cell (e.g. a car battery), uses a chemical reaction to continually separate charges, resulting in a potential difference (voltage) between the two terminals that makes electric charges flow through wires.

DRAFT

The flow of electric charges from one place to another along a pathway made from an electrical conductor is called an electric current. An electric current comes from the movement of negatively charged electrons along a closed conducting pathway called an electric circuit. For historical reasons, the direction of the current is given as the flow of positive charges from the positive terminal of the energy source to the negative terminal. This flow of positive charges is referred to as a conventional current (Figure 3). As electrically charged particles move around an electric circuit, they carry energy from the energy source (such as a battery) to the device that transforms the energy (such as a light globe, motor or heater). An example of the movement of electrical energy in a simple circuit is shown in Figure 4.

Electric circuits must have an energy source, wires to carry the charges and a load that transforms the electrical energy into heat, light or kinetic energy. Many devices have “gaps” called switches to control the flow of electricity in a circuit. If the switch is open, the pathway is broken and no electricity flows. Circuits must therefore be closed for electricity to flow through them.

Drawing circuit diagrams

We use circuit diagrams to represent electric circuits. Each component of an electric circuit is represented by a symbol, as shown in Figure 5 and Figure 6.

In a circuit diagram, wires are usually drawn as straight lines that are joined at right angles (though there are exceptions to this). In Figure 5, the longer line on the battery symbol indicates the positive terminal, and the shorter line indicates the negative terminal. Each terminal is where the wires are connected. When you draw a circuit diagram, use a ruler and a pencil, and make sure all lines are connected to indicate there are no breaks in the circuit.

circuit diagram a diagrammatic way to represent an electric circuit

Measuring electric current

Electric current (symbol I ), or the flow of charge over time, is measured by counting the number of electrons that go past a point in the circuit in 1 second. The unit of measurement for current is amperes (symbol A). An ampere is a large unit of current, so smaller units, such as the milliampere (1,000 mA = 1 A), are often used. Traditionally, an ammeter (Figure 7A) was used to measure the current passing a particular point in an electric circuit. The ammeter was connected into the circuit so that the current flowed through it. More recently, a multimeter (Figure 7B) is used to measure many different aspects of a circuit, including the current.

electrical conductor a material through which charged particles are able to move

electrical insulator a material that does not allow the movement of charged particles insulator a substance that prevents the movement of thermal or electrical energy semiconductor a material that has properties between conductors and insulators; its conductivity increases by adding some impurities to it

Electrical conductors and insulators

An electrical conductor is a material through which charged particles are able to move. An electrical insulator is a material that does not allow the current of charged particles to move. Most wires are made of copper, a metal, with a plastic coating around the outside. Copper is an electrical conductor – electrons are able to move through it easily. Plastic, however, is an electrical insulator. The wires are coated in plastic to prevent the current being “lost” to the surroundings as it passes through the wires.

Some substances are better insulators or better conductors than others. It depends on how easily they allow electrons to move through them; that is, whether they offer more or less resistance to the movement of charges. Air is a good resistor because it is difficult for charged particles to move freely.

Some substances, such as germanium and silicon, are insulators in their pure form, but become conductors if they are combined with a small amount of another substance. These materials are called semiconductors

Within a single silicon chip, very thin layers of silicon are combined with other substances to make that layer a conductor. Complex microcircuits used in computing are made in this way.

Check your learning 2.4

Check your learning 2.4

Retrieve

1 Identify the charge on the following particles. a Protons b Electrons

2 Define the term “current”.

Comprehend

3 Describe how objects can become electrostatically charged.

4 Explain the purpose of a battery in a circuit.

5 Describe an electric circuit.

6 Describe why silicon is called a semiconductor.

7 Compare a conductor and an insulator.

Analyse

DRAFT

8 Compare the flow of electric current in a circuit made with copper wire to one made with rubber wire.

Apply

9 If living organisms are good conductors and air is a good resistor, discuss why it would be dangerous to stand out in an open area during a lightning storm.

10 Draw a circuit diagram containing a battery, a switch and two light bulbs connected one after the other.

11 You are given a plastic rod and a metal rod. Design a simple experiment to test which rod is a better conductor of electricity.

Lesson 2.5 Skills lab: Understanding resistor colour codes

Aim

To use the coloured banding of a resistor to determine its value

Materials

A selection of coloured resistors

Method

Carbon resistors typically have four colour-coded bands on their case (Figure 1). These bands are part of a code that allows you to work out their approximate value and tolerance. The fourth band is the tolerance band, which indicates the amount that the resistance may vary by (the relative accuracy of the resistor). Gold means 5 per cent tolerance, silver means 10 per cent tolerance and no fourth band means 20 per cent tolerance. The lower the percentage tolerance, the more accurate (or closer to the true value) the resistor is.

To read the other three bands, put the tolerance band on the right and start at the other end. The first two bands form a two-digit number according to their colour (see Table 1). The third band tells you how many zeroes to put after the number.

0 Green 5

1

6

2 Violet 7

3 Grey 8 Yellow 4 White 9

Look at the resistor in Figure 2. What does its code mean?

1 The tolerance band is gold, so the resistor has 5 per cent tolerance.

2 The first band is blue, so it has a value of 6.

3 The second band is red, so it has a value of 2. The number is now 62.

4 The third band is also red, so this means 2 zeroes need to be added to the number. The number is now 6,200.

5 Resistor values are always coded in ohms, so the value of this resistor is 6,200 ohms or 6.2 kilo-ohms.

Collect a resistor from your teacher and use the coloured bands to determine its value.

Questions

1st digit 2nd digit Multiplier

Tolerance

Figure 2 Calculate the value of this resistor.

1 Define the electrical term “resistance”.

2 Explain why different resistors are used in different circuits.

3 Explain what is meant by the term “tolerance”.

Lesson 2.6 Investigation: Demonstrating electrostatic electricity

Purpose

To model and explain electrostatic electricity

Materials

• Plastic comb

• Woollen cloth

• Rice Bubbles

• Large plastic bag with tie

• Plastic rod or pen

• Small pieces of paper

• Balloons

• Balloon pump

• Felt-tipped pens

• String

• Tape Procedure

Part A

1 Place some of the Rice Bubbles in the plastic bag. Blow air into the bag and seal it with the tie.

2 Rub the woollen cloth over both the plastic bag and the comb.

3 Bring the plastic bag and comb together.

4 Record what happens.

5 Explain your observations, using the idea of electrostatic charge.

Part B

Part C

1 Using the balloon pump, blow up a balloon and carefully draw a face on it.

2 Tie the balloon onto a string and suspend it from a doorway or ceiling using tape, so that it is level with your head.

DRAFT

1 On a piece of paper, draw four positive and four negative charges. Show what happens to these charges when the positively charged woollen cloth is brought close to them.

2 Rub the plastic rod or pen with the woollen cloth

3 Bring the paper and the plastic rod or pen together.

4 Record what happens and explain your observations, discussing the movement of charges.

3 Rub the balloon face with the woollen cloth and walk towards it.

4 Record what happens.

– Identify the distance you have to be from the “balloon face” before it is attracted to you.

– Describe what happens if you put a piece of paper between you and the balloon.

5 Blow up another balloon and draw a face on it.

– Describe what happens when you bring it close to your suspended balloon.

Discussion

1 Describe your observations in part A using the terms “like charges”, “unlike charges” and “neutral or no charge”.

2 Describe your observations in part B using the terms “like charges”, “unlike charges” and “neutral or no charge”.

3 Describe your observations in part C using the terms “like charges”, “unlike charges” and “neutral or no charge”.

Lesson 2.7

Current can flow through series and parallel circuits

Key ideas

→ In a series circuit, the loads are connected one after the other, and the current is the same throughout the circuit.

→ In a parallel circuit, the loads are parallel to one another, and the current is shared between them.

→ A short circuit occurs when the electrical energy can move through an easier path with less resistance.

Series and parallel circuits

When two or more loads, such as globes, are connected in a circuit, two different types of connection are possible. In a series circuit, the loads are connected one after the other so that the current goes through one load and then through the second load (Figure 1A). In a parallel circuit, the circuit has two or more branches and the current splits between the branches (Figure 1B) and comes back together afterwards.

Comparing circuits

If two globes are connected in a circuit in series, then all the current (moving electrons) passes through both globes (Figure 1A). This means the current is always the same at all points in a series circuit.

If two globes are connected in parallel, however, the current splits (Figure 1B). This means that when the electrons reach the point where the wire splits, the electrons will travel along one path or the other. Part of the current passes through each globe and then joins together again after passing through the globes. This means the currents going through each globe must be added together to determine the total amount of current coming from the battery.

Figure 1 (A) In a series circuit, the current is the same anywhere in the circuit. (B) In a parallel circuit, the sum of the current going through globe A and globe B is equal to the total current.

Learning intentions and success criteria

load a device that transforms electric potential energy into other forms of energy such as heat or light series circuit  the positioning of loads (e.g. lights) side by side in an electric circuit so that the electrical energy passes through one load at a time parallel circuit the positioning of loads (e.g. lights) in an electric circuit so that they are connected to the battery separately; they are in parallel to one another

Figure 2 Traditionally, party lights were a series circuit. This meant that when one light broke, all the lights went out. Now, most modern party lights are arranged in a parallel circuit.

Worked example 2.7A Calculating currents

In a series circuit, a break at any point in the circuit (e.g. from a switch) affects all the globes in the circuit. In a parallel circuit, a break in one of the branches of the circuit affects only the current (and globe) in that branch.

In a household, lights and appliances are connected in parallel so that:

• some appliances can be on while others are off (achieved by inserting switches)

• if one appliance fails, the others will still work (Figure 2).

If the current leaving a battery is 6 amperes (A), calculate the current travelling through two identical lamps if they are connected:

a in series

b in parallel.

Solution Steps

What to do

a. For part a , you need to remember that is the lamps are connected in series, then the electrons will flow through each lamp.

b. For part b, you need to remember that if the lamps are connected in parallel, the electrons are divided equally between the lamps.

DRAFT

Working out

The current in each lamp is 6 A

6 A ÷ 2 l ight bulbs = 3 A i n each light bulb

Batteries in series and in parallel

Batteries may be connected in series or in parallel, in a similar way to globes. When batteries are connected in series, each electron picks up a certain amount of energy as it passes through the first battery and then an additional amount as it passes through the second battery. This arrangement allows electrons to be given larger amounts of energy. For instance, a simple torch normally has two 1.5 V batteries connected in series. As each electron passes through both batteries, it collects the total amount of energy provided by both batteries, which is 3 V. When batteries are connected in parallel, each electron passes through either one battery or the other. This means each electron collects the same amount of energy as it would from one battery on its own. The advantage of this arrangement is that the two batteries last longer than either one of them would in the same circuit on their own.

Short circuit

A short circuit occurs when a conductor with very low resistance is connected in parallel to a component in the circuit. This causes the current (moving electrons) to flow along a different path from the one intended. This can be caused by damaged insulation that usually surrounds the wires or by another shorter conductor, such as water, providing an easy path for the electrons. Electric charges will always take the path of least resistance. This means that large currents can flow through any short path or conductor that allows the electrons to move most easily. Short circuits are dangerous because they can also lead to wires heating up from the fast flow of electrons, causing damage or even fire.

Fuse

A fuse is an electrical safety device designed to protect a circuit from excessive current. It consists of a thin wire or filament that melts when the current flowing through it exceeds a certain limit. This causes a break in the circuit so that the electrical energy stops flowing, preventing damage to other components. Fuses are commonly used in household appliances and electrical systems to prevent damage from overloads or short circuits.

short circuit a condition in an electrical circuit that allows the current to flow along an unintended path resistance a measure of how difficult it is for the charged particles in an electric circuit to move fuse a switch or wire that stops the flow of current if it starts moving too fast

1 Identify the advantages of having a safety switch or fuse in the electric circuits of your house.

2 Describe how you could determine whether the globes in a set of party lights are connected in series or in parallel. (Hint: How does current flow through a series circuit and a parallel circuit?)

Analyse

DRAFT

Figure 3 A sudden increase in current will cause a fuse or safety switch to break the circuit. This stops the current from flowing and may prevent electrocution.

3 Contrast the movement of current in a series circuit and a parallel circuit.

4 Three identical lamps were connected in series to a battery that produced a 12 A current. Calculate the current flowing in each lamp.

Apply

5 Infer how the household appliances are connected in your house (in series or in parallel). Justify your answer (by explaining how series and parallel circuits behave and providing an example that matches your explanation).

6 Double adaptors and power boards enable you to connect additional appliances to a power point. Explain whether the double adaptors or power boards are more likely to be series or parallel connections. Justify your answer.

7 An electrician wanted to connect four identical lamps to a 6 A source so that two lamps had a current of 6 A a nd the other two lamps had a current of 3 A. Create a circuit diagram to show a possible arrangement of the lamps the electrician could use.

8 Draw a series circuit diagram using Figure 4.

Skills builder: Planning investigations

9 Electricians and scientists use diagrams to explain how something needs to be set up. You have been asked to plan an investigation into the wiring of the apartment in Figure 5. Apply your understanding of circuit diagrams to create one for the wiring of this apartment. (THINK: How does each light bulb receive electricity? Have I drawn this scientifically? What are the correct symbols to use?)

10 You need to include the following:

DRAFT

one light bulb and one switch in the kitchen

two light bulbs and one switch in the bedroom

– two light bulbs and two switches in the lounge room

– one light bulb and one switch in the bathroom.

Lesson 2.8 Investigation: Making series and parallel circuits

Purpose

To compare the current in series and parallel circuits

Materials

• Two 1.2 V globes and holders

• 1.5 V battery and holder

• Eight connecting wires (with banana plugs or alligator clips)

• Switch

• Ammeter or multimeter

Procedure

1 Construct four circuits, placing the switch so that it controls:

a both globes, with both either on or off at the same time

b one globe only, with the other on all the time c the other globe only, with the first globe on all the time

d both globes, with one globe on when the other is off and vice versa.

DRAFT

Complete step 2 before you disconnect each circuit.

2 Draw the circuit diagram to show where the switch was placed in each circuit. Connect an ammeter at different places in each circuit and measure the current at each point.

Discussion

1 Describe the effect of changing the location of the switch in a simple circuit.

2 Describe how an ammeter should be connected to measure the current in a circuit.

3 Describe how the current did or did not change when the ammeter’s location was changed.

Lesson 2.9 Voltage, current and resistance

Key ideas

→ Voltage is a measure of the difference in electrical potential energy carried by charged particles between different points in a circuit.

→ Voltage can be measured using a voltmeter or multimeter in parallel to the circuit.

→ Resistance is a measure of how difficult it is for the current to flow through part of the circuit.

Learning intentions and success criteria

voltage a measure of the amount of energy in joules given to a unit of charged particles passing through a battery potential difference the difference in electrical potential energy between two points of a circuit for each unit of charged particle; also known as voltage drop load a device that transforms electric potential energy into other forms of energy such as heat or light

Voltage

Each charged particle has electrical potential energy as it moves in an electric circuit. This energy is given to the charged particles by the battery. The potential difference (voltage) across a battery is a measure of the amount of energy, in joules, given to a unit of charged particles passing through it. This electrical potential energy can be transformed into sound as it moves through a speaker, or into light and heat if it moves through a globe. This means the energy of a charged particle (electron) decreases as it passes through the speaker or globe. The difference in electrical potential energy between two points of a circuit for each unit of charged particle is called potential difference (also known as voltage drop). A component of a circuit that transforms electrical potential energy into other forms of energy and across which a potential drop occurs is called a load

Voltage is measured by a voltmeter or a multimeter in the unit volts (symbol V). To measure the potential difference or voltage between any two points of a circuit, voltmeters are set in parallel across the two points in the circuit that you want to measure (Figure 1).

Batteries add energy to charged particles. The amount of energy added by the battery can be determined by connecting a voltmeter in parallel to the battery. The electrical potential of a charge travelling through a 1.5 V battery changes from 0 V to 1.5 V, meaning the charge gains energy from the battery and its electrical potential energy increases. As the charge moves through the circuit, its energy is converted into other forms, such as light, heat or mechanical energy, depending on the components in the circuit. The charge then returns to the battery where it gains energy again, and this process continues as long as the circuit is functioning.

In a series circuit, the potential energy contained by each electron must be divided between the different loads. This means a 12 V battery connected to two identical light bulbs in series may transform 6 V of energy to each bulb. If the two globes are connected in parallel, each electron moving in a light bulb is able to transform all the 12 V into light and heat.

Worked example 2.9A Calculating voltage

DRAFT

If a 6 V battery is connected to two identical light bulbs, calculate the voltage drop across each lamp if they are connected:

a in series

b in parallel.

Solution

Steps

What to do

a. For part a , you need to remember that if the light bulbs are connected in series, the electrons must divide the voltage (potential energy) between the bulbs.

b. For part b, you need to remember that if the bulbs are connected in parallel, the electrons will separate at the fork in the wires and carry all the energy to each bulb.

Working out

Resistance

The amount of current flowing in a circuit is determined by the resistance (symbol R ) of the circuit. The electrical resistance of a material is a measure of how difficult it is for charged particles to move through. Electrons collide with the atoms in the wires and the various other components of a circuit, and some of their electrical energy is converted or transformed into heat. Most connecting wires are thick and made of good conductors. They have very low resistance, and so hardly any energy is lost by the electrons. The wires in a toaster, however, are designed so that a lot of the electrons’ energy is transformed into heat – so much so that the wires glow red-hot and brown our toast.

Resistors are devices that are placed deliberately in circuits to control or reduce the size of the current. Resistance is measured by a multimeter in units called ohms (symbol Ω).

A rheostat is a variable resistor, used to control the amount of current in a circuit. It consists of a coil of wire, a slider and two terminals: one fixed and one moving. Some rheostats have three terminals, but only two are typically used. When using the fixed terminal, A, and the moving terminal, B, the resistance of the rheostat decreases as the slider moves closer to point A (Figure 3 and Figure 4).

A potentiometer is another type of variable resistor, with a dial that rotates. A light-bulb dimmer is a potentiometer, as is the temperature control on an oven.

Ohm’s law  a law stating that electric current is proportional to voltage and inversely proportional to resistance

Ohm’s law

Georg Ohm, a German physicist, discovered the relationship between voltage, current and resistance. Ohm found that the voltage drop across a fixed-value resistor is always directly proportional to the current through the resistor. This means that, as the voltage goes down, the current will also go down. This relationship is known as Ohm’s law and is written as:

V = IR

where V is voltage in volts (V), I is current in amps (A) and R is resistance in ohms (Ω).

To help us remember Ohm’s law, we can use the Ohm’s law triangle (Figure 7).

If you plot a graph of current versus voltage, the graph is a straight line. Resistance equals one divided by the gradient of the current–voltage graph (Figure 8). Resistors that have a constant resistance are called ohmic resistors because they obey Ohm’s law.

Some resistors do not obey Ohm’s law. These resistors are called non-ohmic resistors. The resistance of a non-ohmic resistor, such as a light globe, changes with temperature. Ohm’s law applies only to ohmic resistors. The current–voltage graph of a non-ohmic resistor is not linear (Figure 9).

Figure 7 The Ohm’s law triangle is used to remember the equations for Ohm’s law. To find resistance (Ω), cover the R; the other two letters show you the formula to use. The V is over the I, so R=VI. The same method is used to find current (I ). To find voltage, cover the V, and multiply I by R.

V (V)

Figure 8 Graphical representation of Ohm’s law

Current, I (A)

Voltage, V (V)

Figure 9 Current versus voltage graph of a non-ohmic resistor

Worked example 2.9B Calculating resistance

If a 9 V battery produces 6 A of current, calculate the resistance of the circuit. Solution

Steps

What to do

Working out

a. State the known and unknown information. V = 9 V, I = 6 A, R = ?

b. Substitute the values into R=VI and solve for R, including units. R=9V6A=1.5 Ω The resistance in the circuit is 1.5 Ω.

Check your learning 2.9

Check your learning 2.9

Retrieve

1 Define the terms:

a voltage

b rheostat

c resistance.

2 Complete the information in Table 1.

Table 1 Symbols and units for electric circuit terms

Term Symbol Unit

Current I

Voltage V

Resistance

Comprehend

Explain what happens to the electrical energy carried by electrons as they flow around an electric circuit.

Analyse

3 Identify the three equations that can be obtained by rearranging the Ohm’s law triangle.

4 Calculate the current flowing through a 44 Ω resistor when it has a voltage drop of 11 V across it.

5 Calculate the change in voltage across a 25 Ω resistor when a current of 50 mA (0.05 A) flows through it.

6 Calculate the value of a resistor that has a voltage drop of 8 V across it when a current of 0.4 A flows through it.

Table 2 Experimental results for an electric circuit

Apply and create

7 A group of students performed an experiment to determine the value of an unknown ohmic resistor. They made a simple circuit and measured the amount of current for different values of voltage. Their results are shown in Table 2.

a Determine the independent, dependent and controlled variables.

b Draw a current–voltage graph for the data in Table 2.

c Calculate the resistance using the gradient of the graph.

d Another group of students performed the same experiment but each time they changed the voltage and thickness of the connecting wires. Evaluate the validity of their experiment.

Skills builder: Conducting investigations

8 When you conduct investigations around electricity, there are different risks to consider compared with investigations involving chemicals. It is particularly important that your equipment is set up and assembled safely.

a Identify risks associated with connecting the power source before you have set up your circuit. (THINK: What risks exist when wires aren’t connected correctly?)

b Explain why it is important that you check wires before commencing an investigation. (THINK: Would your results be impacted?)

Lesson 2.10 Investigation: Investigating Ohm’s law

Purpose

To investigate the voltage drop across a resistor and the current flow through a resistor, and to calculate the average value of the resistance

Materials

• 10 Ω resistor

• Voltmeter

• Ammeter

• 2–12 V power supply

• 3 other resistors with masking tape over their coloured bands

• Connecting wires

Procedure

1 Identify the 10 Ω resistor. It should be colourcoded brown, black, black.

2 Connect the circuit as shown in Figure 1. Connect the voltmeter around the resistor. Use the DC terminals of the power supply and start with the dial on 2 V.

3 Switch on the power supply, take the readings on the ammeter and voltmeter, and switch the power off again straight away (so you don’t overheat the resistor).

4 Repeat step 3 three times and record your measurements in Table 1.

5 Change the dial on the power supply to 4 V and repeat steps 3 and 4. Then change the dial to 6 V and repeat steps 3 and 4 again.

6 Repeat the experiment for the other three resistors, without reading their coloured bands.

7 Complete the results table for each of the three masked resistors and calculate their resistance.

8 Determine the average resistance of each resistor.

9 Remove the masking tape and determine the resistance values from the coloured bands of the resistors.

Results

Copy and complete Table 1.

Discussion

1 From your results table, calculate the values in the last column.

2 For the three masked resistors, compare the accuracy of the values you obtained to the values indicated by their coloured bands.

3 Use the formula below to calculate the difference (error) between the two values as a percentage of the marked value.

4 % error = × 100

marked value − average calculated  value marked value

5 Identify which value – the one obtained by reading the coloured bands or the one obtained from your calculations – provides the most useful measure of a resistor’s resistance. Justify your answer (by explaining how each value is obtained, describing which value is most relevant to use in a circuit and deciding which value provides the most useful measure).

Conclusion

Describe what you know about Ohm’s law.

Table 1 Experiment results

Lesson 2.11

How is power measured?

Key ideas

→ The unit of measurement for power is the watt (W), which is the amount of energy used per second.

→ To determine how much you pay for electricity, a power meter is installed and read, then a bill sent out.

→ The energy star rating system is a visual guide to show consumers how energy eff icient an appliance is. The more stars, the more energy efficient.

Introduction

The electrical potential energy of charged particles in an electric circuit decreases as they move through loads such as light bulbs, toasters and fans. These devices transform electrical energy into other forms of energy, such as light, heat or kinetic energy. Different electrical devices convert energy at different rates. For example, a 100 watt light bulb running for 10 hours would use 1 kilowatt-hour of energy. A 1,000 watt microwave would use 1 kilowatthour of energy in just 1 hour.

Energy consumption

The rate at which energy is transformed is called power (P ), and its unit of measurement is the watt (W). If an electrical device uses 1 W of power, it means it consumes 1 J of energy per second. For example, a 100 W light bulb uses 100 J of energy every second. The amount of energy used by appliances in your home determines how much you pay on your electricity bill. To measure energy usage, electricity companies use a unit of measurement called the kilowatt-hour (kWh). This is the amount of energy a 1-kilowatt appliance uses in 1 hour. There are 1,000 W in 1 kilowatt (kW), so if you have a 1,000 W appliance running for 1 hour, it uses 1,000 W × 1 hour = 1,000 watt-hour, or 1 kWh.

Learning intentions and success criteria

power  the rate at which energy is transformed in a circuit

watt unit of power; 1 watt is equal to 1 joule per second kilowatt-hour unit used by electricity companies to measure electricity usage; it is equal to the amount of energy used (in kilowatts) in one hour

Electricity companies typically charge a certain rate per kWh, which is listed on your electricity bill. For instance, if the cost is $0.10 per kWh, running a 1 kW appliance for 1 hour would cost you 10 cents.

A power meter is a device that measures the power used by an electrical device. Using a power meter can help you monitor how much electricity an appliance uses, which can help you save energy and reduce electricity costs. Power meters are easy to use; you simply plug the power meter into an electrical outlet and then plug the electrical device into the power meter (Figure 1). The power meter will show you how many watts the device uses.

Calculate kWh by following these steps.

1 Divide the power in W by 1,000 to convert them to kW.

2 Multiply the kW calculated in step 1 by the number of hours the device was used.

To work out how much the electricity costs, multiply the kWh (calculated in step 2) by the cost of electricity per kWh on your electricity bill.

Worked example 2.11A Energy consumption

Calculate the energy in kWh that a 3,500 W air conditioner uses in 2 hours.

a If the cost of electricity is $0.20 per kWh, calculate the cost of running the air conditioner for 2 hours.

Solution

Steps

What to do

a. For part a , to convert W to kW, divide the power in W by 1,000.

b. To calculate the energy used in kWh, multiply the kW by the number of hours the device was used.

c. For part b, to calculate the cost of running the air conditioner for 2 hours, multiply the kWh by the cost of electricity per kWh.

DRAFT

Working out

Energy star rating

Scientists are constantly trying to design the best appliances possible with the highest efficiency ratings. This makes the appliances better for the environment and less costly to power. Do you and your family always buy the most efficient appliances? Are you familiar with the star ratings on appliances?

The energy star rating labels provide two important pieces of information about the device: a star rating and the energy consumption per year. A device can have between 1 and 6 stars. The more stars, the more energy-efficient the appliance is, meaning it uses less energy than a model of similar size and features. Not only is it good to know that less energy is being wasted, but it also means that, on your electricity and gas bills, you are paying for energy that is being used rather than for energy that is being thrown away. The other information on an energy star rating label is the energy consumption of the device. It shows how much electricity a device uses in kWh per year (Figure 2).

Check your learning 2.11

Check your learning 2.11

Retrieve

1 Define the term “power”.

Comprehend

2 Explain the purpose of the energy star rating labels.

3 Explain why two appliances with the same power rating might have different energy star ratings.

Analyse

4 Calculate:

a the electrical energy (in kWh) used by a 300 W refrigerator in 24 hours

b the cost of using the refrigerator for 24 hours if each kWh costs $0.20.

5 Calculate:

a the energy in kWh that a 100 W laptop uses in 8 hours

b the cost of running the laptop for 8 hours if the cost of energy is $0.20 per kWh.

Apply

6 For three days in a row, record the reading on your family’s electricity meter at exactly the same time each day (e.g. 6 pm).

a Calculate the number of kWh your family used in the first 24-hour period (subtract the second reading from the first). Then calculate the number of kWh your family used in the second 24-hour period.

b Calculate the approximate cost of each 24-hour period’s electricity, assuming that each kWh costs $0.20. (What information do I have? Where do I need to place this in an equation?)

c List all the electrical appliances your family used during this time (e.g. electric hot water, kettle, electric stove and/or oven, computers, TV).

d Identify the items in part c that you think used the most energy during this time, using the information from their energy star rating.

e Compare the energy efficiency of the items in part c using their energy star rating.

Lesson 2.12

Investigation: Comparing the energy transformed over time

Purpose

To investigate energy transformation over time

Materials

• 30 cm nichrome wire

• Wires

• Alligator clips

• Power supply

• Ammeter

• Voltmeter

• Calorimeter

• Thermometer

• Stirring rod

• 100 mL measuring cylinder

• Stopwatch

Procedure

Part A: Prepare the heating coil

1 Wrap the nichrome wire around a pencil to form a coil shape. Ensure the coils do not touch each other.

Part B: Set up the circuit

2 Use alligator clips and wires to connect the two ends of the nichrome wire (heating coil) to the power supply.

3 Place an ammeter in series with the circuit to measure the current.

4 Place a voltmeter parallel to the heating coil to measure the voltage drop.

Part C: Prepare the calorimeter

5 Fill the calorimeter cup with 100 g (100 mL) of cold water.

6 Insert the thermometer into the water. Make sure it doesn’t touch the sides or bottom of the cup.

7 Record the initial temperature of the water.

Part D: Placing the heating coil in the calorimeter

8 Gently place the nichrome heating coil into the calorimeter cup. Ensure the coil is fully submerged in the water and is not touching the bottom of the calorimeter cup.

9 Secure the coil in place by either of the following methods.

– Attach the coil to a small piece of string or thread, which can be tied to the top of the calorimeter. This keeps the coil from touching the bottom of the cup or the sides of the calorimeter.

Part E: Start the experiment

10 Set the voltage of the power supply to 2 V.

11 Turn on the power supply and start the stopwatch immediately.

12 Set the current to 1 A by adjusting the voltage. Make sure the current is maintained at 1 A.

13 Record the voltage at 1-minute intervals throughout the experiment.

14 Monitor the temperature of the water using the thermometer.

15 Continue the experiment until the water’s temperature increases by about 10°C.

DRAFT

– Use a small clamp or stand to hold the coil just above the bottom of the cup while ensuring it is still submerged in water. If you use a clamp, make sure it does not touch the wire directly to avoid any unwanted energy loss.

16 Turn off the power supply.

17 Stir the water gently to ensure uniform temperature distribution.

18 Record the final temperature of the water.

Calculations

Calculate input energy

1 Calculate the power used in each 1-minute time interval by multiplying the current by the voltage drop (P = I × V ). Record this in the results table.

2 Multiply the power value for each interval by 60 seconds to calculate the energy used in each time interval (energy = power × time).

3 Add together the energy used in all time intervals to calculate the total electrical energy used during the experiment.

Calculate the heat absorbed by the water

4 Calculate the heat absorbed by the water (q) using the formula:

5 q = mass of water (g) × 4.18 × (final temperature − initial temperature)

Results

1 Note the initial and final temperatures.

2 Copy and complete Table 1.

Table 1 Experiment results

Discussion

1 What type of energy transformation occurred in this experiment?

2 Compare the heat absorbed by the water (q) to the total energy input of the circuit.

Lesson 2.13

3 Explain any discrepancies between the calculated energy and the heat absorbed by the water.

Energy efficiency can reduce energy consumption

Key ideas

→ When cooking food, you do not want to lose heat energy to the surroundings or else it will take longer for the food to cook.

→ Insulation prevents the transfer of thermal (heat) energy.

→ The use of traditional ground ovens by Aboriginal and Torres Strait Islander Peoples demonstrates their understanding of energy efficiency, ensuring that heat energy is retained during the cooking process.

DRAFT

Being energy efficient

For thousands of years, Aboriginal and Torres Strait Islander Peoples have used their understanding of the way energy is transferred and transformed to develop energy-efficient ways to generate heat and to cook food and not lose the heat energy to the surroundings.

Cooking food

One role of archaeologists is to develop an understanding of traditional methods used by Aboriginal and Torres Strait Islander Peoples to cook food. With the permission of the Barengi Gadjin Land Council Aboriginal Corporation, which represents the Traditional Owners of the Jadawadjali language group in Western Victoria, archaeologists set out to recreate a traditional ground oven. They dug a large pit, 25 cm deep, in the earth and lined the base of the pit with spheres made of clay and sand. On top of the spheres, a fire was slowly built up until it burned strongly for 1 hour (Figure 1A–E). When the fire died down to glowing coal, half the coals and spheres were removed (Figure 1F). Wet reeds were placed on top of the remaining coals and clay spheres (Figure 1G) before the edible roots of Microseris scapigera (yam daisy) were placed on top of the reeds. The remaining hot coals and spheres (Figure 1H) were placed on top of the roots before being covered with large sheets of stringy bark (Figure 1I) and sand (Figure 1J). The food was cooked overnight. This process of using the reeds, stringy bark and sand to insulate the heat, reduced the loss of heat and increased the efficiency of the ground oven.

DRAFT

Heating and cooling your house

You probably use electricity or gas to run heating or cooling systems at home. In a hot environment, energy is needed to remove the heat from inside your home, allowing it to cool down.

The warm air inside the house is moved over cool pipes in an air conditioner. The thermal energy of the house air is passed to the refrigerant inside the pipes and is then carried outside the house. If the house is well designed, thermal energy remains outside and the house stays cool.

Home design features

Architects design homes to help control the flow of thermal energy. They can add a variety of features that help limit the amount of heating or cooling your house needs.

Insulation

Lining the inside of the walls, floors and roof of your house can ensure that heat is not transferred between the outside air and the inside of the house. This keeps the heat inside on a cold day and outside on a hot day.

Reducing window heat

One of the main places that heat is transferred is through windows. On a hot day, light and heat from the Sun can easily penetrate a window. This transfers heat into the house.

An awning on a window can limit this. Limiting the number of windows facing the Sun can also help to prevent the heat being transferred into the house.

Double-glazed windows have two panes of glass, separated by an air gap (Figure 3). Air does not transfer heat very well (it is a good insulator). A home with double-glazed windows will not gain much heat during a hot day or lose heat on a cold night.

Verandas

Verandas work much like awnings, but also prevent heat and light from the Sun from shining on walls. This stops heat from being transferred to the walls and then to the air inside.

DRAFT

Check your learning 2.13

Check your learning 2.13

Comprehend

1 Explain how insulation reduces the need for artificial heating and cooling.

2 Describe how window awnings and verandas keep a house cool in summer. Apply

3 Summarise how architects use their knowledge of energy efficiency to minimise the energy used in a house.

4 The temperature inside and outside a house was measured over 4 days and displayed in Figure 5.

a Determine from the graph whether the house was insulated.

b Justify your answer (by using numbers from the graph as evidence).

Lesson 2.14

Challenge: Design an energyefficient house

Design brief

Design and build two identical model houses out of cardboard or wood. Add a feature to one of the houses that will make it more efficient in staying cool. Test your design feature by exposing both houses to an energy source (a strong light) and determine the rate of temperature increase for each house.

Criteria

DRAFT

• Only one feature may be added to the second house.

• The feature must represent a design feature that is currently available to homeowners.

• The feature must be proportionate in size to the house.

Questioning and predicting

1 Identify the feature you will add.

2 Identify the materials you will use.

3 Use your knowledge of heat energy to explain why your added feature will keep the house cool.

Planning and conducting

1 Explain how you will measure the temperature of the two houses.

2 Draw a table that you will use to collect your data. Include headings and units of measurement.

3 Describe how long you will expose the houses to the energy source.

Processing, analysing and evaluating

1 Create a graph to compare the data from both houses.

2 Describe the rate of temperature increase in both houses.

3 Calculate how efficient your feature was at preventing the transfer of thermal energy by comparing the difference in temperature of the two houses.

4 Describe the limitations of your design (when it will not prevent thermal transfer).

5 Explain how you could create a large-scale version of your design for a real house.

6 Evaluate your design and explain how you would modify it if you were doing this experiment again.

Communicating

DRAFT

Present the various stages of your investigation in a formal scientific report.

Learning intentions and success criteria

Lesson 2.15 Electricity is generated from different energy sources

Key ideas

→ Global energy consumption has increased since 1900.

→ The world is moving towards a greater reliance on electrical energy.

→ Electrical generators transform kinetic energy into electrical energy.

Introduction

The world’s energy consumption is increasing as populations grow and people become wealthier. This global rise in energy demand has prompted efforts worldwide to develop alternative sources of energy and to become more energy-efficient.

Global energy consumption

Global energy consumption has increased almost every year since 1900 (Figure 1). Until the mid-1800s, the main sources of energy were renewable, such as wood and waste from agriculture (e.g. animal dung and excess plant material), which were burned for heating and cooking. These sources of energy are called “traditional biomass” (Figure 1). After the mid-1800s, the use of fossil fuels rapidly expanded. Since 1900, the majority of energy has come from coal, oil and natural gas, which are non-renewable energy sources. Today, fossil fuels remain the dominant energy source worldwide, although the use of renewable sources is growing.

Global primary energy consumption by source

Primary energy (1) is based on the substitution method (2) and measured in terawatt-hours (3).

renewables

gas

Figure 1 Global primary energy consumption

Primary energy: raw energy sources (like coal or solar) before conversion, including both usable energy and losses. The substitution method: adjusts non-fossil energy to match fossil fuel inefficiencies for fair comparison, using a standard efficiency factor (~0.4). A watt-hour: a unit of energy equal to 1 watt used for 1 hour (3,600 joules), often measured in kWh, MWh, etc.

Australia has abundant fossil fuels, and coal is its main energy source (Figure 2). There is increasing awareness of the environmental impact of continually burning fossil fuels, and pressure is being put on politicians to consider climate change when managing the use of these energy sources. Reducing Australia’s dependency on fossil fuels would decrease the environmental damage caused by their combustion and the effects of climate change.

Per capita energy from fossil fuels, nuclear and renewables, 2023

Measured in kilowatt-hours of primary energy consumption per person, using the substitution method

The rate of growth in electricity generation has outpaced the growth in total energy consumption by 25 per cent. This suggests that the world is shifting towards greater reliance on electrical energy, highlighting the need to explore alternative energy sources for electricity generation.

There are many ways to generate electricity. Electrical generators convert kinetic energy into electrical energy. Turbines, which consist of a series of blades mounted on a pole, drive electricity generators. Different sources of energy, such as water, steam and wind, can be used to rotate a turbine’s blades. The turbine is attached to a generator, and the kinetic energy of the turbine is transferred to the generator. The generator then converts this energy into electrical energy.

Generating electricity using renewable sources of energy

Solar energy

Solar energy is the most abundant source of energy. The Sun emits solar radiation as light. Solar energy technologies, such as solar panels, take this light energy and transform it into electrical energy. This process is called photovoltaic effect. Solar panels are also called photovoltaic panels.

turbine a large wheel with angled sections called vanes, like a propeller, that is used to generate electricity

generator a machine that uses the electromagnetic effect to separate charges and produce electricity

Wind energy

Wind energy is the kinetic energy of moving air. Wind turbines transform this kinetic energy into electrical energy. A wind turbine is the opposite of an electric fan which transforms electrical energy into kinetic energy. Wind turbines consist of large blades mounted on a tower. As the wind blows, it causes the blades to spin which turns a generator to produce electricity. Wind farms, which are collections of wind turbines, can be found both onshore and offshore.

Hydropower

hydropower energy produced by falling water that turns turbines to generate electricity

DRAFT

geothermal energy energy that comes from heat beneath Earth’s surface biomass organic matter (material from organisms such as plants and animals); a renewable resource that can be used to generate energy biofuel a renewable energy source derived from organic materials, including plants and animal waste

Hydropower uses the gravitational potential energy of water moving from a higher elevation to a lower point. As the water flows to the lower level, its gravitational potential energy decreases and is converted to kinetic energy, according to the law of conservation of energy. The kinetic energy of the water is used to turn a turbine and generate electricity. Hydropower plants can be found in various forms, including large dams, run-of-the-river systems and pumped storage systems. These plants provide a significant portion of the world's renewable energy.

Snowy Hydro 2.0 is the largest renewable energy project in Australia, located in NSW. It links two dams at different heights: the Tantangara and the Talbingo. Water will be pumped from the lower dam to the upper dam when there is less demand for electricity. When more electricity is needed, the water from the upper dam will be released back down to the lower dam, transforming gravitational potential energy into kinetic energy. The kinetic energy of water turns a turbine which generates electricity by converting kinetic energy into electrical energy. This project will help provide reliable, renewable energy.

Geothermal energy

Geothermal energy is heat energy from under the Earth’s surface. Steam turbines are used to transform this heat energy into electrical energy. Geothermal power plants typically use steam produced from reservoirs of hot water found a few miles or more below Earth’s surface. The steam is brought to the surface through wells and used to drive turbines connected to generators.

Biomass

Biomass is an organic energy source. It can come from a variety of sources, such as wood, crops and animal waste. When biomass is burned, it releases energy that is used for heating, electricity generation and transportation. These biofuels can be used in place of fossil fuels.

Generating electricity using coal

Fossil fuels are burned to heat water and generate electricity using steam turbines. Coal, a non-renewable energy source, is still widely used in Australia for electricity generation. The energy stored in coal is converted into electrical energy in a power station. Since coal is inexpensive and readily available in Australia, there has been resistance to adopting emerging renewable technologies, such as solar power, hydropower and wind energy. Despite this reluctance, scientists are working to encourage the use of these renewable sources and to find more sustainable methods of using coal. Many people in today’s society, particularly younger generations, increasingly seek renewable energy sources and adopt more sustainable lifestyles. While the transition to renewable energy is important, some scientists are exploring methods to reduce the environmental impact of using coal.

Coal washing

Coal washing removes impurities from the coal. In this process, coal is crushed and mixed with liquid, allowing contaminants to separate. The coal is then burned, and the harmful gases produced are treated with limestone and water to remove sulfur dioxide. Nitrogen oxides can also be reduced, using burners that limit the oxygen involved in the combustion process.

Coal gasification (IGCC)

Another technique is the Integrated Gasification Combined Cycle (IGCC) system, which transforms coal into gas for energy production. The IGCC process uses steam and pressurised hot air to break apart the carbon molecules in coal. This method is more energyefficient than directly burning coal to generate heat for turning a turbine.

Carbon capture and storage (CCS)

When carbon dioxide is emitted from power plants, it can be captured and stored through carbon capture and storage (CCS). Several methods have been developed to capture carbon dioxide, including the following.

• Flue-gas separation captures carbon dioxide using steam, which is then condensed into a concentrated stream.

• Oxy-fuel combustion is a process in which coal is burned in pure oxygen, creating a gas composed mostly of carbon dioxide and water vapour, without sulfur dioxide or nitrogen oxides. The carbon dioxide is then stored in containers, either deep underground or under the ocean, where it dissolves.

Individual choices and future developments

In our daily life, the energy choices we make – such as which appliances to purchase –can have an impact on energy consumption. Some appliances are more energy efficient than others, helping to reduce overall energy demand. Scientists, including engineers, biologists, chemists and physicists, are collaborating to develop new, more sustainable energy sources. Their work will play a crucial role in creating a future where energy consumption is both environmentally responsible and efficient.

coal washing the process of “cleaning” coal with water and chemicals to remove sulfur and other impurities before it is burned at a coal power plant

DRAFT

Check your learning 2.15

Check your learning 2.15

Retrieve

1 Identify the two waste gases other than carbon dioxide that result from burning coal.

2 List three renewable sources of energy used to generate electricity.

Comprehend

3 Summarise the environmental benefits of using solar power over coal.

4 Explain how hydroelectric power stations convert kinetic energy into electrical energy.

Analyse

5 Use the graph in Figure 1 to identify past trends in energy use and predict future energy demands at global levels.

6 Compare the environmental impact of electricity generation from coal, wind and solar.

Apply

7 Predict the impact on electricity output if wind speed decreases on a wind farm.

8 The use of coal in Australia is widely debated. Coal has negative environmental impacts, and people sometimes suggest Australia should use

renewable energy sources, specifically nuclear energy. This is suggested because Australia has one of the largest uranium stores on Earth.

a Research nuclear power as a source of energy.

b Evaluate nuclear energy and coal energy, considering ethical issues and how sustainable they are.

Skills builder: Conducting investigations

9 Research two sources of information related to the use of coal in Australia. Then investigate two sources of information related to renewable energy in Australia.

a List the references for each source.

b Discuss whether one source was better than the other.

10 Scientists assess strategies that are identified as possible solutions to a problem. An example of a problem and a possible solution is coal and coal washing. Evaluate the method of coal washing by writing a pros and cons list. (THINK: What is the value of coal washing? What are the outcomes of coal washing? Are there better alternatives?)

Learning intentions and success criteria

Key ideas

→ Solar energy is converted into electrical energy using solar cells.

→ Solar energy is stored in a battery as chemical potential energy, which can be used when needed.

Introduction

A solar cell is any device that transforms the Sun’s light energy into electrical energy. The number of households using the Sun’s light energy to heat water or power heating and cooling devices is growing rapidly every year.

Using solar energy in Australia

Australia is often known as the sunburnt country. This is a reference to the large number of hours each day that the Sun shines. Australia is a big country, however, and the number of hours the Sun shines varies greatly, depending on the location and the time of year. Solar energy is often measured as the number of peak sunlight hours every day (Figure 1). This is then averaged out over the whole year. For example, in the Hunter Valley in NSW, the number of peak hours can be as low as 4.0 hours/day in winter and as high as 6.5 hours/day in summer. Over a year, this averages out to 5.6 hours/day. In Tasmania, the average number of peak hours is 3 hours/day. In Queensland, the Northern Territory and Western Australia, the average number of peak hours each day is 6.

energy the energy from sunlight that can be converted into electrical or heat energy

Converting energy from the Sun

DRAFT

Using energy from sunlight to power a house has its problems. The most common time people use electrical energy is when sunlight is least available. This means that the light energy from the Sun needs to be stored so it can be used at night. This light energy is transformed into potential chemical energy in a battery so it can be used to heat water, provide light or supply energy for cooking (Figure 2).

Figure 4 History of solar cars; the following parts are labelled:

1 1883: The first solar cell was invented by Charles Fritts. A solar cell is selenium (a semiconductor) with a thin layer of gold.

2 1941: The silicon solar cell was invented by Russel Ohl and had an efficiency of 1 per cent.

3 1954: Gerald Pearson, Calvin Fuller and Daryl Chapin improved the efficiency of the silicon solar cell to 6 per cent. Silicon strips were used to create the first solar panels.

4 1955: The first solar car invented was a tiny 35 cm vehicle created by William G. Cobb of General Motors.

5 1962: International Rectifier Company designed the first solar car that could be driven. They converted a vintage 1912 Baker electric car to run on approximately 10,640 PVCs.

6 1977: Alabama University professor Ed Passerini constructed his own solar-powered car called “Bluebird”.

7 1980: Englishman Alain Freeman road-registered a threewheeler solar car with a solar panel on the roof.

8 1980: Arye Braunstein and colleagues at Tel Aviv University (Israel) designed a solar car with a solar panel on the roof and hood of the car. The car was recorded reaching 65 km/h with a maximum range of 80 km.

photovoltaic cells (pv cells) solar cells that transform solar energy into electrical energy; also known as pv cells

DRAFT

9 1982: Australian brothers Larry and Garry Perkins designed and hand-built the “Quiet Achiever”, the first vehicle driven across a continent using only solar power. Larry and Hans Tholstrup drove the Quiet Achiever from the east coast of Australia to the west coast. Their feat is recognised in the World Solar Challenge, a solar car race that allows designers to compete in a race across Australia every 2 years.

10 1987: GM Sunraycer completed a 3,010 km trip in California with an average speed of 67 km/h.

11 2014: A solar-powered family car (with four seats) called “Stella” was driven 613 km from Los Angeles to San Francisco.

Capturing the light energy

Solar panels are a collection of solar cells called photovoltaic cells (PV cells). When light shines on the surface of PV cells, the light energy is transformed into electrical energy. The most efficient PV cells currently convert 30 per cent of the energy they receive from the Sun.

Alternatives to fossil fuel cars

Since the beginning of the 1900s, people have relied on cars to move from one place to the next. Cars rely on the chemical energy in fossil fuels (petrol and diesel) to generate the kinetic energy to move. This energy transformation from chemical energy to movement energy has contributed to the carbon dioxide that is warming the atmosphere. As a result, scientists and engineers are working to develop alternative forms of energy transformation.

Hybrid cars combine combustion engines that use fossil fuels with electric motors that use energy stored in a battery. The car uses the electric motor at low speeds and the combustion engine when accelerating and travelling at faster speeds. Hybrid cars cannot be plugged into the energy grid to charge the battery. Instead, the battery is recharged by converting kinetic energy (from when the car brakes or coasts) into electrical energy and storing it in the battery. Electric cars use the chemical energy in batteries to generate kinetic energy. The batteries can be charged through the same electrical grid that powers your house. They can also use solar panels to transform sunlight into electrical energy, which can be stored as chemical potential energy in the battery.

Solar cars use a variety of solar panels to transform light energy into kinetic energy. Most current solar-powered vehicles only carry one person (Figure 3). They are lightweight (approximately 600 kg) so that they are more energy efficient.

Check your learning 2.16

Check your learning 2.16 Retrieve

1 Define the following terms: a Tesla Powerwall b photovoltaic cell.

2 Recall why Australia is known as the sunburnt country. Analyse

3 Explain why it is important to store solar energy.

4 Compare the carbon footprint of fossil fuel cars, hybrid cars and electric cars. Apply

DRAFT

5 Investigate the challenges electric cars face in terms of battery life and charging infrastructure.

6 Imagine your family needs to buy a car and asks your opinion on choosing between a fossil fuel car, a hybrid or an electric car. Which option would you suggest? Explain your choice in terms of cost and environmental impacts.

Skills builder: Processing and analysing data

7 The amount of (photovoltaic) sunshine available across Australia changes according to the time of the year (Figure 6). Photovoltaic data is collected by a number of Australian research groups to track the effectiveness of energy transformation from light energy to electrical energy.

8 Analyse the graphs by answering the questions below.

a Identify the variable on the horizontal x-axis.

b Identify the variable on the vertical y-axis.

c Identify Queensland’s maximum percentage of photovoltaic capacity from the graphs.

d The data was collected at different times of the year. Evaluate the energy efficiency of the different seasons by answering the following.

e Identify which graph has the highest value.

f Explain how the different seasons affect the level of sunshine available in Queensland.

g Decide which season produces the highest percentage of photovoltaic capacity.

h Evaluate which state is capable of transforming the most light energy into electrical energy through the use of PV cells by answering the following.

i Identify which state has high percentages of photovoltaic capacity in both seasons.

j Explain why transforming light energy across the whole year is more important than transforming the most light energy in just one season.Decide which state is capable of transforming the most light energy into electrical energy.

Time of day in summer

NSW Performance

NT Performance

QLD Performance

SA Performance

TAS Performance

VIC Performance

WA Performance

Lesson 2.17

Review: Energy Summary

Lesson 2.1 Energy cannot be created or destroyed

• The law of conservation of energy states that energy cannot be created or destroyed.

• When energy is transformed, waste energy is produced.

• Efficient energy transformations produce less waste energy.

Lesson 2.2 Sankey diagrams can represent energy efficiency

• The conservation of energy can be represented in a Sankey diagram.

Lesson 2.4 Electricity can flow through circuits

• A closed circuit occurs when the positive and negative charges can be separated and reunited.

• An electrical conductor allows the charges to flow easily.

• An electrical insulator restricts the movement of the charges.

Lesson 2.7 Current can flow through series and parallel circuits

• In a series circuit, the loads are connected one after the other, and the current is the same throughout the circuit.

• In a parallel circuit, the loads are parallel to one another, and the current is shared between them.

• A short circuit occurs when the electrical energy can move through an easier path with less resistance.

Lesson 2.11 How is power measured?

• The unit of measurement for power is the watt (W), which is the amount of energy used per second.

• To determine how much you pay for electricity, a power meter is installed and read, then a bill sent out.

DRAFT

Lesson 2.9 Voltage, current and resistance

• Voltage is a measure of the difference in electrical potential energy carried by charged particles between different points in a circuit.

• Voltage can be measured using a voltmeter or multimeter in parallel to the circuit.

• Resistance is a measure of how difficult it is for the current to flow through part of the circuit.

• The energy star rating system is a visual guide to show consumers how energy efficient an appliance is. The more stars, the more energy efficient.

Lesson 2.13 Energy efficiency can reduce energy consumption

• When cooking food, you do not want to lose heat energy to the surroundings or else it will take longer for the food to cook.

• Insulation prevents the transfer of thermal (heat) energy.

• The use of traditional ground ovens by Aboriginal and Torres Strait Islander Peoples demonstrates their understanding of energy efficiency, ensuring that heat energy is retained during the cooking process.

Lesson 2.15 Electricity is generated from different energy sources

• Global energy consumption has increased since 1900.

• The world is moving towards a greater reliance on electrical energy.

• Electrical generators transform kinetic energy into electrical energy.

Lesson 2.16 Solar cells transform the Sun’s light energy into electrical energy

• Solar energy is converted into electrical energy using solar cells.

• Solar energy is stored in a battery as chemical potential energy, which can be used when needed.

Review questions 2.17

Review questions Module 2

Retrieve

1 The units of voltage, current and resistance, respectively, are:

A amps, ohms and volts

B ohms, volts and amps

C volts, amps and ohms

D volts, ohms and amps.

2 A 50 Ω resistor is connected to a 10 V battery. The current flowing through it is __________.

3 If the voltage is doubled, then the current will be __________.

A 5 A, 2.5 A

B 0.2 A, 0.1 A

C 5 A, 10 A

D 0.2 A, 0.4 A

4 A voltmeter is connected in __________ in a circuit, and an ammeter is connected in __________ in a circuit.

A series, series

B parallel, parallel

C series, parallel

D parallel, series

5 Identify the circuit in Figure 1 as either parallel or series.

6 Identify each symbol (ammeter, cell, globe or switch) in Figure 2.

9 Identify the correct labels for A, B and C in Figure 3.

7 Define the term “resistance”.

8 In your own words, describe Ohm’s law.

Comprehend

10 Describe how current moves in a parallel circuit.

11 Figure 4 shows a block of ice melting.

a Describe what is happening to the molecules as the ice melts. Draw a diagram to illustrate your answer.

b Explain where the energy to melt the ice comes from. Explain how the energy is transferred to the molecules of ice.

Analyse

12 Draw a circuit diagram showing a battery and a switch, with a globe on either side of the switch.

a Does it matter where in the circuit the switch is placed?

b Show the direction of electron flow and the direction of conventional current.

13 Calculate the current flowing through a 30 Ω resistor when it has a voltage drop of 12 V across it.

14 Calculate the voltage drop across a 50 Ω resistor when a current of 25 mA flows through it.

15 Calculate the value of a resistor that has a voltage drop of 18 V across it when a current of 0.3 A flows through it.

16 Draw a circuit diagram showing a battery, three globes and a switch that turns off the whole circuit. Two globes are in series, while the third globe is in parallel with the other two globes.

17 Explain why your home is wired in parallel.

18 Consider why it is scientifically incorrect to say that the fridge passed on its cold energy to you.

19 Compare current and voltage.

20 Calculate the current flowing through a 30 Ω resistor when it has a voltage drop of 12 V across it.

21 Calculate the voltage drop across a 50 Ω resistor when a current of 25 mA flows through it.

Apply

22 Assess the use of coal in Australia to generate electricity.

23 Explain why your home is wired in parallel.

24 Aboriginal and Torres Strait Islander Peoples have used possum, kangaroo and wallaby skin coats to keep themselves warm. Traditionally, the skin was worn with the fur facing towards the body to reduce heat loss. Use your understanding of the transfer of thermal energy to discuss the effectiveness of this strategy.

25 Rubber and wood have very high resistance to the flow of electricity. Propose how this will affect the current and voltage in a circuit.

Critical and creative thinking

26 A storm has blown a tree over on the main power line to your neighbourhood. The electricity supply is cut. Describe your day without electricity.

27 Investigate two sources of information related to the use of coal in Australia. Then investigate two sources of information that provide an alternate energy source in Australia.

a Write down references for each source.

b Discuss whether one source is better than the other.

28 Construct a fair experiment to investigate the effect of increasing resistance on the current.

a Write a hypothesis for the experiment.

b Determine independent, dependent and controlled variables.

c Write a method for performing the experiment.

d Draw a labelled scientific diagram of the equipment set-up.

30 Use your understanding of current and voltage to create a model of the flow of electricity through a circuit. You might use people or even an animation as your model.

Research

31 Choose one of the following topics for a research project. A few guiding questions have been provided, but you should add more questions that you wish to investigate. Present your report in a format of your own choosing. marked value − average calculated  value marked value

32 Incandescent light globes

DRAFT

29 The use of coal in Australia causes debate among people. Coal has negative environmental impacts, and people sometimes suggest Australia should use renewable energy sources, specifically nuclear energy. This is suggested because Australia has the largest uranium stores on Earth.

a Investigate nuclear power as a source of energy.

b Create a table to compare nuclear energy and coal energy.

Incandescent light globes are traditional light globes. You are likely to see them around homes. What does “incandescent” mean? What are incandescent light globes made of? Why must the filament be contained in an inert gas like argon? What temperature does the filament need to be heated to so that it gives off light? How efficient are incandescent light globes?

Generating electricity

Australia is powered via coal energy, which is created at coal power stations. Why do they need to burn coal? What is water steam used for? How can wind energy or any other renewable resources be used instead of coal?

Energy-efficient housing

In previous societies, energy efficiency was important because people had limited access to the types of energy supplies and their applications that we have today. Research how civilisations in tropical areas designed their homes to keep them cool and damp-free. What different types of energy-efficiency practices have humans used through the ages? Imagine your family needs to buy a car and asks your opinion on choosing between a fossil fuel car, a hybrid or an electric car. Which option would you suggest? Explain your choice in terms of cost and environmental impacts.

Aabsolute dating

a method of determining the age of a fossil by measuring the amount of radioactivity remaining in the rock surrounding the fossil acceleration the change of velocity over time acceleration due to gravity the acceleration of an object due to a planet’s gravitational field; on Earth, g = 9.8 or 10 m/s2

accommodation the process where the shape of the eye’s lens changes to focus images of objects at different distances

accuracy how carefully, correctly and consistently data has been measured or processed; in science, how close a measured value is to the true value achondroplasia

a genetic (inherited) disorder of bone growth resulting in abnormally short stature and short limbs

acid

a hydrogen-containing substance that has the ability to donate a proton action force the force acted on one object by another object

active site

the region of an enzyme to which substrates can bind

adaptation

a characteristic or behaviour of a species that allows it to survive and reproduce more effectively alkaline solution

a solution that consists of a base dissolved in water

alkali

alpha particle

a radioactive particle containing two protons and two neutrons; can be stopped by a piece of paper

amino acid

the building blocks of proteins, consisting of an amino group, a carboxyl group and a variable side chain

amyloplast

a specialised plant organelle packed with starch granules and used in geotropism

analogous structures

structures in organisms of different species that have the same function but are structurally different because they evolved independently; for example, wings in birds and bats

anecdotal

based on personal accounts rather than facts or research

angle of incidence

the angle between the incident ray and the normal (the line drawn at right angles to a reflective surface)

angle of reflection

the angle between the reflected ray and the normal (the line drawn at right angles to a reflective surface)

angle of refraction

the angle between a refracted ray and the normal (a line drawn at right angles to the surface where refraction occurs)

anion

a negatively charged ion; an anion has more electrons than protons

anther

the end part of a stamen (male part of a flower); contains pollen

antibody

a molecule produced by B cells that binds to a specific pathogen

artificial passive immunity

the temporary immunity that occurs when a person receives ready-made antibodies from an outside source

asbestosis

a lung disease caused by the inhalation of asbestos fibres

asexual reproduction

reproduction that involves a single organism producing offspring that are genetically identical to itself

atomic number

DRAFT

a base that dissolves in water alkane

an organic compound that only includes carbon and hydrogen atoms

allele

a version of a gene; a person inherits two alleles for each gene, one coming from each parent

allopatric speciation

a mode of speciation that occurs when a population is geographically separated into two or more isolated groups, preventing gene flow between them

antidiuretic hormone (ADH)

a hormone that regulates the amount of water in the body

antigen

a substance that triggers an immune response, such as a molecule on the surface of a pathogen or an allergen

apoptosis

programmed cell death

artificial active immunity

the long-lasting immunity that develops after a vaccination when the immune system is exposed to a weakened version of a pathogen

the number of an element in the periodic table, which equals the number of protons in that element

atom

the smallest particle of matter; cannot be created, destroyed or broken down (indivisible)

audible

able to be heard

autonomic nervous system

the part of the nervous system that controls involuntary actions such as heartbeat, breathing and digestion

autosomal dominant

an inheritance pattern in which only one copy of a gene (from either parent) carried on a non-sex chromosome is sufficient to cause the presence of a trait or disorder

autosomal recessive

an inheritance pattern in which two copies of a gene (one from each parent) carried on a non-sex chromosome are required for an individual to express the trait or disorder

autosome

a chromosome that does not determine the sex of an organism

auxin

a plant hormone that plays a crucial role in regulating growth and development

average speed

the total distance travelled divided by the total time taken

axon

a long projection of a neuron that carries electrical impulses away from the cell body to other neurons, muscles or glands

B cell

an immune cell that produces antibodies in response to pathogens

base

a substance that has the ability to accept a hydrogen proton

beta particle

a radioactive particle (high-speed electron or positron) with little mass; can be stopped by aluminium or tin foil

bias

leaning towards or against an idea by being prejudiced or unfair

binary fission

a form of asexual reproduction used by bacteria; the splitting of a parent cell into two equal daughter cells

bioaccumulation

the build-up of harmful substances in living organisms

biodegradable

a material that can be broken down naturally by living organisms, like bacteria, into harmless substances over time

biodiversity

the variety of life; the different plants, animals and microorganisms and the ecosystems they live in biofuel

a renewable energy source derived from organic materials, including plants and animal waste

biofuel

a renewable energy source derived from organic materials, including plants and animal waste

biomass

organic matter (material from organisms such as plants and animals);

a renewable resource that can be used to generate energy

bioplastic

a type of plastic made from renewable biological sources, such as plants, rather than fossil fuels

biotechnology

the use of living organisms or their parts to develop products and technologies, often to improve human life or the environment

bivariate data

Bohr model

the model of the atom developed by Niels Bohr in the 1910s, with electrons placed in shells centred on the nucleus

budding

asexual reproduction that involves a new organism developing from a bud on the parent and eventually detaching bulb

a short, fleshy stem surrounded by layers of modified leaves; serves as a storage organ and a means of vegetative reproduction

Ccarbon tax

a tax levied on the carbon content of fuels used by businesses or homes

carbon trading scheme

the process of allocating a set limit of carbon credits to businesses, which can then trade the credits

carcinogen

a substance that can cause cancer

carpel

the female reproductive structure of a flower, consisting of the stigma, style and ovary

carrier

a person who has the allele for a recessive trait that does not show in their phenotype

catalyst

a substance that increases the rate of a chemical reaction without undergoing any permanent chemical change cation

a positively charged ion; a cation has more protons than electrons causal relationship

a cause-and-effect relationship where one event or action directly leads to another cell body

cerebrum

the largest part of the brain; divided into four lobes called the frontal lobe, the parietal lobe, the temporal lobe and the occipital lobe

cervix

the narrow neck connecting the uterus and the vagina

chromatid

one side of the X-shaped chromosome that contains a double helix of DNA chromosome

the form of DNA that is tightly wound around proteins (histones) before replication

DRAFT

data that involves two variables and aims to explore the relationship between them

blind study when the participants do not know if they are receiving the treatment or a placebo

blue shift

the shift in the frequency of light towards higher frequencies, or the blue end of the spectrum, as the source of light and the observer move towards each other

the central part of a neuron that contains the nucleus and organelles cell line

a cell culture developed from a single cell and therefore consisting of cells with a uniform genetic make-up cell mutation

a change in a cell’s DNA due to exposure to mutagens

central nervous system

the brain and spinal cord

centromere

the structure in a chromosome that holds two chromatids together

cilia

tiny hair-like structures on the surface of cells

circuit diagram

a diagrammatic way to represent an electric circuit

circular economy

a system that minimises or eliminates waste by reusing, recycling and regenerating materials

climate

the weather conditions at a particular place, averaged over a long period of time, based on the collection and analysis of large amounts of data

climate change

the change in global climate patterns, including temperature, over time

closed system

a system that does not allow matter to enter or leave but does allow energy to be transferred in or out

coal washing

the process of “cleaning” coal with water and chemicals to remove sulfur and other impurities before it is burned at a coal power plant

codon

a group of three nucleotides on mRNA

collision theory

in order for a reaction to occur, the reacting particles must collide with enough energy and at the correct angle

colloidal particles

particles small enough to remain evenly distributed in a mixture but larger than the particles in a solution combustion

a reaction that involves oxygen and releases light and heat energy competition the struggle between individuals or groups for limited resources

complementary base

a nucleotide base that pairs with its partner nucleotide on the alternative DNA strand; adenine pairs with thymine, and guanine pairs with cytosine compostable

a material that can break down into rich soil (compost) under specific conditions, without leaving harmful residues

concave

refers to a lens or mirror that is thinner in the centre than at the ends conclusion

a statement that “answers” the aim of an experiment

conductor

a material or substance that electrons can flow through; the flow of electrons through a conductor is electrical current confirmation bias

a bias when a scientist selects a method that will support the outcome they want confounding variable a variable that is not measured but may impact the results of an investigation

con

a disadvantage that is a risk or unfavourable outcome

consequentialism

an ethical framework focused on the outcome of an action or decision continental drift the continuous movement of the continents over time continuous data

data that is measured and can be any value, such as height, mass, speed, temperature and distance continuous spectrum a spectrum that contains all wavelengths of light control centre

the part of an organism, typically the brain or spinal cord in animals, that processes and responds to information received from receptors control group

convergent evolution

the process whereby unrelated organisms evolve to have similar characteristics as a result of adapting to similar environments

convex

refers to a lens or mirror that is thicker in the centre than at the ends

Coriolis effect

the influence of Earth’s rotation on the direction of movement of air or water cornea

a thin, transparent material that protects the eye and refracts light correlation

a relationship between two or more variables

correlation coefficient

a number between −1 and 1 that quantifies the strength and direction of a linear relationship between two variables; often represented by “r ”

cosmic microwave background radiation

remnant electromagnetic radiation left from early stages of the Universe covalent bond

a chemical bond involving the sharing of electrons between atoms; the sharing of electrons creates a stable electron configuration within the atoms

credible information that is reliable, trustworthy and based on evidence

CRISPR-Cas9

a gene-editing tool that allows for easy and accurate modifications to DNA, enabling researchers to “cut” and “paste” genes in a way that can change how an organism functions critical angle the angle of incidence when the refracted angle is 90°

cross-linked polymer

cultural protocol

the customs, values and guidelines that shape behaviour and interactions within a specific cultural group, ensuring respectful and appropriate interactions cytokinesis the splitting of a replicating cell into two cells

Ddeciduous

a type of plant that loses its leaves during the cooler months to conserve energy when there is less sunlight; annual shedding of leaves

decomposition

DRAFT

a group of organisms, chemical reactions or physical conditions that can be compared to the group that has had the independent variable changed controlled variable

a variable that is kept constant and unchanged throughout an investigation conventional current the f low of positive charges in a circuit converge when rays of light move towards a single point

a polymer consisting of multiple long polymer chains that have been linked together to form a threedimensional structure cross-pollination

the exchange of pollen and ova between different plants of the same species crossing over a process during meiosis where homologous chromosomes exchange segments of genetic material, leading to increased genetic variation in the resulting gametes

cultural norm

the expectation that you should behave according to the values of the people around you

a reaction that involves the breakdown of a compound into simpler substances delocalised electrons

electrons that are not restricted to a single atom or covalent bond dendrite

the part of a neuron (nerve cell) that receives a message and sends it to the cell body

deontology

an ethical framework focused on the intent of an action or decision dependent variable

a variable in an investigation that may change as a result of changes to the independent variable descriptive statistics methods used to summarise and describe the main features of a data set diatomic molecule

a molecule that is composed of two atoms of the same or different chemical elements

dilation

widening of the pupil to allow more light to enter the eye

diploid

containing two complete sets of chromosomes

discrete data

data where the numbers can be separated into different groups

displacement

a vector quantity that measures the change in position of an object and its direction over a certain period of time

displacement reaction

a reaction resulting in the displacement of an atom or group of atoms distance

how far an object has travelled in a set time

diverge when rays of light move away from each other

divergent evolution

the process whereby related species become more dissimilar over time due to different environmental pressures, resulting in distinct traits from a common ancestor

DNA (deoxyribonucleic acid)

a molecule that contains all the instructions for every job performed by the cell; this information can be passed from one generation to the next DNA replication

the process by which a cell makes an identical copy of its DNA dominant allele

a gene variant that expresses its trait in an organism's phenotype even if only one copy is present

dominant trait

a characteristic that needs only one copy of an allele to appear in the physical appearance of an organism double displacement reaction an exchange of ions from the two reactants to form two new products

double-blind study

when neither the participants nor the treating doctors know if they are receiving the treatment or a placebo

dry cell

contains dry substances and uses a chemical reaction to produce electrical energy; commonly used for portable devices such as a torch battery

Eearly detection and predictive testing for adults

the testing of chromosomes for the presence of alleles that increase the probability of cancers forming echolocation

the ability to use sound to navigate and hunt

ecological footprint

measure of the environmental impact of a person, community or country by calculating the amount of land and water needed to provide resources and absorb waste, especially carbon emissions

ectoparasite

a parasite that lives on the host (e.g. a tick)

ectotherm

an animal that is unable to regulate its own body temperature effector

a cell, tissue or organ that responds to a stimulus

elastomer

a long chain of polymers occasionally linked together like a ladder

electric charge

a property of subatomic particles (electrons and protons) that results in electric energy; electric charge can be positive or negative

electric circuit

a closed pathway that conducts electrons in the form of electrical energy

electric current

the flow of electrical charge through a circuit

electrical conductor

a material through which charged particles are able to move

electrical insulator

a material that does not allow the movement of charged particles

electromagnetic wave

a transverse wave that transfers energy through space without any need for a medium

electron configuration

the arrangement of electrons of an atom, placed in electron shells centred on the nucleus

electron shells

the placement of electrons around an atom’s nucleus; an atom may have one or more electron shells

electron

a negatively charged particle that moves around in the space outside the nucleus

electroreception

endemic

always found in a specific location

endocrine system

a collection of glands that make and release hormones

endometrium

the lining of the uterus

endoparasite

a parasite that lives inside the host (e.g. a tapeworm)

endotherm

an animal that regulates its own body temperature

energy

the capacity to do work

energy efficiency

DRAFT

the ability to sense electric fields generated by other animals

electrostatic charge

economic sustainability practices that manage environmental, economic and social factors to support long-term economic growth and development today, without compromising this ability for future generations

economy the supply of money and goods and services that are produced, distributed and consumed

an electric charge between two objects caused by a deficiency or excess of electrons (negative charges)

element

a pure substance made of only one type of atom

emission spectrum

the pattern of coloured lines of light that are seen through a spectroscope when an element is heated

a measure of how much input energy is transformed, rather than lost (via sound or heat)

enhanced greenhouse effect

the additional effect that humans are having on the natural greenhouse effect due to the burning and release of fossil fuels

enriching

increasing the proportion of a specific component in a mixture

environmental sustainability practices to maintain, manage and minimise damage to natural resources today so they are available for the future needs of generations

enzyme

a protein-based catalyst

epidemic

a widespread outbreak of an infectious disease that is typically isolated to a specific region

epididymis

a coiled tube behind the testes that carries sperm to the vas deferens

ethical framework

a structured system of principles and values that guides individuals and organisations in making decisions about right and wrong

ethics

a set of principles that provide guidance to determine what is morally right and wrong

eukaryotic

an organism with cells that contain a nucleus and membrane-bound organelles; protists, fungi, plants and animals have eukaryotic cells

eutrophication

excess nutrients in a body of water that can cause the rapid growth of algae (algal blooms) and damage to aquatic ecosystems

evolution

the process by which populations of organisms change over successive generations through variations in their genetic material

evolutionary relationship

the way in which two species or populations are related with respect to their evolutionary descent external fertilisation

the union of male and female gametes outside the female reproductive tract extinct refers to when there are no living members of the species left extrapolation

estimating unknown values from trends in known data

Ffallopian tubes

tubes that connect the ovaries to the uterus

fermentation

an anaerobic process of breaking down sugars fertilisation

the union of male and female gametes filament the stalk or slender part of a stamen, which holds the anther, where pollen is produced

focal length

the distance from the middle of the lens to the focus

foetus

an unborn animal or human after the embryo stage; in humans, this is after 8 weeks of development

force

a push or pull that, if unbalanced, can cause a change in an object's motion or shape

fossilisation

the process of an organism becoming a fossil

fossil

Ggamete

a reproductive cell (sperm in males and ova in females) that carries half the genetic information necessary for the formation of a new organism

gamma ray

a high-energy electromagnetic ray released as a part of radioactive decay; can be stopped by lead gene cloning

the production of identical copies of a gene

gene editing

a method that allows scientists to make precise changes to an organism’s DNA to alter its traits

gene flow

the flow of genes from one generation to the next, or from one population to the next, as different families or groups in the population choose partners and mate

gene pool

all the genes or alleles in a population

gene therapy

a medical technique that involves altering the genes inside a person’s cells to treat or prevent disease; it aims to correct or replace faulty genes with healthy ones to improve health outcomes

generator

a machine that uses the electromagnetic effect to separate charges and produce electricity

gene

a segment of DNA that codes for a specific trait

genetic code the sequence of nucleotides in DNA, inherited from parent organisms

genetic disorder

genetic screening

the testing of populations or groups to identify individuals at risk of genetic disorders, even if they do not show symptoms

genetic technology techniques that involve manipulating the genetic material (DNA) of organisms to change their characteristics or functions

genetic testing

testing that examines an individual’s genetics to identify changes or mutations that may indicate a genetic disorder or an increased risk of developing certain diseases

DRAFT

the remains or traces of an organism that existed in the past fragmentation

asexual reproduction in which an organism breaks into fragments, each capable of growing into a new individual frameshift mutation

a type of mutation in which a nucleotide is added or deleted, causing a shift in the reading frame of codons; usually results in a deformed protein

fuse

a switch or wire that stops the flow of current if it starts moving too fast

a condition caused by abnormalities (mutations) in the DNA (genes); genetic disorders are inherited (passed from parent to child)

genetic drift

a random evolutionary mechanism that causes changes in allele frequencies within a population’s gene pool over time

genetic engineering the deliberate engineering of change in the DNA of an organism

genetic predisposition an increased chance of developing a disease due to genetic (inherited) characteristics

genetically modified organism (GMO)

an organism that has had its DNA changed in a laboratory genome

the complete set of genetic material present in an organism, including both coding and non-coding DNA

genotype the combination of alleles for a particular trait geothermal energy energy that comes from heat beneath Earth’s surface geotropism the growth or movement of a plant in the direction of gravity (positive geotropism) or against gravity (negative geotropism)

gestation the length of time between fertilisation and birth

global warming potential (GWP)

a measure of how much impact a gas will have on atmospheric warming over a period of time compared to carbon dioxide

gonadotropin-releasing hormone (GnRH)

a hormone produced in the hypothalamus that plays a crucial role in regulating the reproductive system

greenhouse gas

a gas (carbon dioxide, water, methane) in the atmosphere that can absorb heat groups the vertical columns of the periodic table; elements in each group have the same number of electrons in their valence shell

gymnosperms

seed-producing plants that do not form flowers or fruits, and their seeds are exposed on the surface of cones

HHaber–Bosch process

the method for the production of ammonia

half-life

the time it takes the radioactivity in a substance to decrease by half haploid containing one complete set of chromosomes (n), which is half the diploid number; gametes (sperm and egg cells) are haploid

heredity

the process by which traits and characteristics are passed from parents to offspring through genes heterotrophic

an organism that consumes other organisms to obtain energy heterozygous having two different alleles for a particular trait; a carrier for a recessive trait

hibernation

an extended period of inactivity, typically in response to colder conditions high-pressure system regions where the air pressure is higher than surrounding areas

histamine

a chemical released by mast cells during allergic reactions and immune responses; causes blood vessels to dilate and become more permeable, leading to swelling, redness and itching

histone

a protein that helps package and organise DNA in the nucleus of eukaryotic cells

homeostasis

the process by which the body detects and responds to stimuli to ensure a stable internal state is maintained homologous chromosome pairs

chromosome pairs – one inherited from each parent – that are similar in size, shape and genetic content homologous structures

hydrocarbon

a molecule that contains only carbon and hydrogen atoms

hydrogen bond

a type of weak chemical bond between two groups of atoms; the bond between two nitrogenous bases in the DNA helix

hydropower

energy produced by falling water that turns turbines to generate electricity hydrotropism

the growth or movement of plant roots towards or away from moisture

hyperglycaemia

a condition resulting from too much glucose in the blood

hypoglycaemia

a condition resulting from too little glucose in the blood

hypothalamus

the region at the centre of the brain that produces hormones and regulates important body functions such as sleep, body temperature and heart rate

hypothesis

a proposed explanation for a prediction that can be tested

Iimage

what is formed when light from an object is reflected by a mirror immune

able to fight infection as a result of prior exposure

immune system

a system of organs and structures that protect an organism against disease incidence the number of new cases of a disease measured over a specific time inconclusive

not leading to a definite conclusion or result

infectious disease

a condition or disorder caused by pathogens such as bacteria, viruses and fungi

inference

a conclusion based on evidence and reasoning

inflammation

the body’s protective response to injury, infection or harmful stimuli

infrasound

sounds that cannot be heard by humans, with frequencies usually below 20 Hz

inorganic compound

a chemical compound that does not have any carbon–hydrogen bonds

insulator

DRAFT

structures that are similar in different species, because those species evolved from a common ancestor, but do not necessarily have the same function now; an example is forelimbs in different mammal species

homozygous having two identical alleles for a particular trait

hormone

a chemical messenger that travels through blood vessels to target cells

independent variable

a variable that is changed in an investigation

indicator

a substance that changes colour in the presence of an acid or a base inert

a substance that does not react with other substances

inertia

the tendency of an object to resist changes in its motion while either at rest or in constant motion

a substance that prevents the movement of thermal or

electrical energy

internal fertilisation

the union of male and female gametes inside the female reproductive tract interneuron

a nerve cell that links sensory and motor neurons; also known as a connector neuron

interphase

a phase of cell life where normal functioning occurs

interpolation

an estimation of a value within the original range of the data intrusion when upwelled waters do not reach the surface

inversely proportional relationship

a relationship between two variables in which the dependent variable decreases as the independent variable increases investigative able to be investigated through measurement and observation

ion

an atom that has either a net positive or negative electrical charge

ionic bond

a chemical bond formed from the electrostatic attraction between oppositely charged ions

ionic compound

a compound that is formed by ionic bonding; ionic compounds consist of both positively and negatively charged ions

ionisation

the process by which atoms become ions by losing or gaining electrons

iris

the coloured part of the eye that controls the dilation and shrinking of the pupil isobar

a line drawn on a weather map that joins places of equal air pressure

isolated system

a system that does not allow matter or energy to enter or leave isolation

the division of a population into two groups

isotopes

different forms of the same element that have a different atomic weight due to a different number of neutrons, but the same number of protons

Jjoule (j)

the unit of energy; its symbol is J

Kkaryotype

a way of representing a complete set of chromosomes, arranged in pairs, in order of decreasing size kilowatt-hour

unit used by electricity companies to measure electricity usage; it is equal to the amount of energy used (in kilowatts) in one hour

kinetic energy

the energy an object or particle has due to its motion

kurtosis indicates how much data resides in the tails (outliers) compared to a normal distribution

Llaw of conservation of energy

a scientific rule that states that the total energy of a closed system and its surroundings is always constant and cannot be created or destroyed law of reflection when light is reflected off a surface, the angle of incidence will equal the angle of reflection

lens

linear polymer

a long single chain of polymers

litmus paper

a paper containing an indicator that turns red when exposed to an acid and blue when exposed to a base living fossil

an existing species of ancient lineage that has remained unchanged in form for a very long time load

a device that transforms electric potential energy into other forms of energy such as heat or light load

a device that transforms electric potential energy into other forms of energy such as heat or light

logbook

a book used to record all the details of experiments or research projects longitudinal wave

a type of (sound) wave where the particles move in the direction of travel of the wave; also known as a compression wave

low-pressure system

regions where the air pressure is lower than surrounding areas

Mmagnetoreception

the ability to sense Earth's magnetic fields

magnitude the size or extent of something

mast cell

a type of white blood cell that plays a role in the inflammatory response; releases histamine, which causes capillary walls to become more permeable

maternal serum screening (MSS) the genetic testing of fetal DNA found in the mother’s blood matter

medium

the matter that waves travel through megafauna

large animals, typically extinct species that were significantly larger than modern-day relatives

meiosis

a specialised type of cell division that reduces the chromosome number by half, producing four genetically unique haploid gametes from a single diploid parent cell

memory cell

an immune cell produced in response to an infection; retains the memory of how to fight the pathogen

DRAFT

anything that has space and volume; it is made up of atoms

mean

a curved piece of transparent material line graph

a graph used to display continuous data that is connected by a line; typically used to demonstrate trends in data line of best fit

the line on a scatter graph that passes through, or nearly through, as many data points as possible to show any overall trends in the data

the average of a set of numbers calculated by adding the numbers and dividing by the total number of values

mechanical waves waves that need a medium to propagate (transfer energy)

mechanoreceptor

a nerve cell that detects pressure or touch

median

the middle value in a sorted data set

Mendelian inheritance

the inheritance patterns of traits controlled by single genes with two alleles, one dominant and one recessive meniscus

the curve at the surface of a liquid in a container menstruation

also known as a period; the process of the endometrial lining of the uterus breaking down and leaving the vagina mesothelioma

an aggressive type of cancer that results from asbestos fibres sticking to the protective layer of the lungs

methodology the overall approach to a scientific investigation

migrate

the movement of an animal from one region to another, typically in response to changing seasons

mineral

a naturally occurring inorganic substance with a definite chemical composition and crystalline structure mitosis

the process of cell division that results in genetically identical daughter cells; allows growth and repair

mode

the value that appears most frequently in a data set

molecular compound

a compound composed of two or more non-metal atoms held together by chemical bonds molecule

a group of two or more atoms connected by chemical bonds; a molecule is the smallest unit of a substance that retains its properties monatomic

an ion consisting of single, isolated atoms that are not bonded together

monogenic inheritance

the inheritance pattern in which a single gene determines traits monogenic trait

a trait determined by one gene with two alleles

monohybrid cross

a genetic cross between two individuals that focuses on the inheritance of a single trait, controlled by one gene with two alleles

monomer

a small molecule that is capable of reacting with other similar molecules to form a long-chain molecule (polymer)

mortality

number of deaths

motor neuron

a nerve cell that carries a message from the central nervous system to a muscle cell; also known as an efferent neuron

mRNA

a molecule that carries the coding sequence for protein synthesis

mutagen

a chemical or physical agent that causes a change in genetic material such as DNA

mutation

a permanent change in a DNA sequence

myelin sheath

a fatty layer that covers the axon of a nerve cell

Nnatural active immunity

the long-lasting immunity that develops when the immune system is naturally exposed to a pathogen, leading to the production of specific antibodies and memory cells

natural greenhouse effect

the natural warming of Earth due to water vapour and other gases being present in small amounts in the atmosphere and affecting Earth’s radiation balance

negative control

an individual test that checks that a negative result is possible in an experiment

negative feedback loop

a regulatory mechanism in which the stimulus causes a response that acts in the opposite direction to whatever is being regulated

net force

the vector sum of all the forces acting on an object; also known as resultant force

neuron

a nerve cell

neurotransmitter

a chemical messenger that crosses the synapse between the axon of one neuron and the dendrite of another neuron

neutral having a pH of 7, so neither an acid nor a base; an example is water

neutron

a neutral (no charge) subatomic particle in the nucleus of an atom

newborn screening the testing of chromosomes in a baby’s white blood cells for the presence of a genetic disease

newton the unit used to measure force, symbol N

Newton’s first law

an object remains at rest or in constant velocity unless acted on by a net unbalanced force; also known as the law of inertia

Newton’s second law

a law describing how the mass of an object affects the way it moves when acted upon by one or more forces; often expressed as F = ma (F = total force on the object, m = mass of the object, a = acceleration)

Newton’s third law for every action, there is an equal and opposite reaction

non-investigable

cannot be investigated through measurement and observation non-specific immune response the generalised response of the immune system to protect the body against all pathogens, rather than targeting a specific pathogen; also called the “innate immune response” non-spuriousness not false or fake

normal

an imaginary line that is drawn at right angles to the surface of a reflective or refractive material

DRAFT

natural passive immunity

the temporary immunity that occurs when a baby receives antibodies in breast milk or through the placenta from the mother

natural selection

the process by which traits that enhance survival and reproduction become more common in a population, while less advantageous traits diminish over generations

noble gases gases with a full electron shell; noble gases are extremely stable and do not easily react with other elements non-disjunction an error in cell division (meiosis or mitosis), where chromosomes fail to separate properly, resulting in daughter cells with an abnormal number of chromosomes non-infectious disease

a condition or disorder caused by environmental or genetic factors rather than pathogens

nuclear fission

when the nucleus of an atom splits into two or more smaller nuclei, with the release of energy

nuclear fusion

the process in which smaller nuclei come together and form a larger nucleus nucleotide

the building block of DNA consisting of one deoxyribose sugar, one phosphate group and one nitrogenous base nucleus (chemistry) the small region at the centre of an atom that consists of the protons and neutrons; plural “nuclei” nutrient a compound that is required for the growth, repair and basic functions of a body; includes proteins, fats, carbohydrates, water, vitamins and minerals

nutritional deficiency a condition caused by inadequate intake or absorption of nutrients, such as proteins, fats, vitamins and minerals

Oobjective

without bias or prejudice observations facts or details based on actual sensory information

ochre

a natural clay earth pigment rich in iron oxide, commonly found in yellow, red and brown hues

octet

a group or set of eight octet rule

where the valence shell of an electron has eight electrons oestrogen a reproductive hormone in females offspring an organism’s young, or child

Ohm’s law

a law stating that electric current is proportional to voltage and inversely proportional to resistance

opaque

a substance that does not allow light to pass through open-cut mining

a surface mining method that digs a large hole to extract minerals near the surface

optic fibre

a thin fibre of glass or plastic that carries information and/or data in the form of light

optic nerve

the connection that sends the electrical signal to the brain to create the image; creates a blind spot where it meets with the retina due to the lack of lightsensitive cells

ore

a naturally occurring solid material from which metals or minerals can be extracted

organic compound

a chemical compound that has carbon–hydrogen bonds

organism

an individual living thing

outlier

a data point that does not fit with the rest of the data

ovum

(plural: ova) the reproductive egg

ovary

a female reproductive organ found in both animals and plants; it produces eggs (ova) in animals and ovules in plants

ovulation

the part of the menstrual cycle when an egg is released from the ovary

Ppandemic

a widespread outbreak of an infectious disease that is spread across multiple global regions

pattern

when a set of data repeats in a predictable way

pedigree

a chart showing the phenotypes of an individual and their ancestors, usually over several generations; also known as a family tree diagram

peptide hormone

a protein-based hormone that is fast acting and relatively short-lived periods

the horizontal rows of the periodic table; elements in each period have the same number of electron shells

peripheral nervous system

all the neurons (nerve cells) that function outside the brain and spinal cord

permafrost

ground that has been frozen since the last Ice Age; stores carbon permeable

a barrier that allows fluids, gases or other substances to pass through it

pH scale

a scale that represents the acidity or basicity of a solution; pH < 7 indicates an acid, pH > 7 indicates a base, pH 7 indicates a neutral solution

phagocyte

an immune cell that surrounds, absorbs and destroys pathogens

phagocytosis

the process by which certain white blood cells engulf and destroy bacteria phenotype

observable physical and physiological traits of an organism, resulting from the interaction between its genotype and environmental influences photon

an elementary particle of electromagnetic radiation that acts as both a particle and a wave photoreceptor

placebo

a substance or treatment that is designed to have no effect

placenta

the organ that connects the developing foetus to its mother

pluripotent

a stem cell that can develop into nearly all cell types in an organism

pollination

the process in which pollen from the male reproductive plant structures is transferred to the female reproductive structure of a plant

pollution

DRAFT

parallel circuit

the positioning of loads (e.g. lights) in an electric circuit so that they are connected to the battery separately; they are in parallel to one another parthenogenesis

asexual reproduction in which an egg develops into a new individual without fertilisation

pathogen

a disease-causing agent such as bacteria, virus or fungi

a cell in the eye that detects light phototropism

the growth or movement of a plant towards or away from light

photovoltaic cells (pv cells)

solar cells that transform solar energy into electrical energy; also known as pv cells

phylogenetic tree

a branching tree-like diagram showing relationships between different taxonomic groups

pituitary gland

a small gland at the base of the brain that produces hormones

the introduction of substances to the environment that can cause harm

polyatomic ion

an ion consisting of two or more atoms that have been bonded together

polygenic

inheritance patterns where multiple genes contribute to a single trait, resulting in a continuous range of phenotypes

polymer

a long-chain molecule formed by the joining of many smaller repeating molecules (monomers)

polymerisation

a chemical reaction where small molecules (monomers) combine to form a long-chain molecule (polymer)

positive control

an individual test that checks that a positive result is possible in an experiment

potential difference

the difference in electrical potential energy between two points of a circuit for each unit of charged particle; also known as voltage drop

poultice

a soft, moist mass of material, often made from herbs, plants or clay, that can be applied to the skin, typically to relieve pain, reduce inflammation or treat infections

power

the rate at which energy is transformed in a circuit

precision

the state of measurements being consistent and repeatable prediction

an outcome that is expected based on prior knowledge or observation

primary colours of light

the three colours of light (red, blue and green) that can be mixed to create white light

primary data

data collected by the person writing the report

probe

a DNA or RNA fragment used to detect complementary sequences in a sample through hybridisation procedure

a series of clear steps that are followed when conducting a scientific investigation; also called a method product a substance obtained at the end of a chemical reaction; written on the right side of a chemical equation prokaryotic

a single-celled organism with no nucleus or membrane-bound organelles; bacteria and archaea are made up of a single prokaryotic cell

pro an advantage where the outcomes are favourable

prostate gland

a walnut-sized structure surrounding the neck of the male bladder that blocks the flow of urine so sperm can move along the urethra protein

a molecule made of long chains of amino acids, essential for the structure, function and regulation of body tissues and organs

proton

a positively charged subatomic particle in the nucleus of an atom pseudoscience incorrect beliefs that are mistakenly thought to be scientific Punnett square

a graphical tool used in genetics to predict the possible genotypes and phenotypes resulting from a cross between two individuals pupil the black, circular opening that controls the amount of light entering the eye

Qradioisotope

an isotope (different versions of the same element due to differing atomic mass) that emits radiation due to an unstable nucleus radionuclide

a radioactive isotope

random error

variability in a measurement in either direction by an unknown cause or causes randomised when people, objects or similar are selected at random reactant

a substance used at the beginning of a chemical reaction; written on the left side of a chemical equation reaction force the force acting in the opposite direction to an initial force reaction rate

how fast a reaction proceeds receptor a specialised cell that detects a stimulus or change in the normal functioning of the body

recessive allele

a gene variant that only expresses its trait when two copies are present recessive gene

a gene that must be present on both chromosomes to be expressed recessive trait

a characteristic that is only expressed in the phenotype when two identical alleles are inherited

recombinant DNA technology

refractive index

a measure of the bending of light as it passes from one medium to another refute

prove a statement to be false or incorrect using evidence regression analysis

a statistical method used to predict how one variable (the dependent variable) changes when another variable (the independent variable) changes relationship

DRAFT

qualitative data

information that is descriptive and cannot be represented by numbers quantitative data information that can be counted or measured; numerical values

Rradioactive decay

the conversion of a radioactive isotope into its stable form, releasing energy in the form of radiation

a range of techniques that use enzymes to cut and join the DNA from different organisms recycle to turn waste into a new material red shift the shift in the frequency of light towards lower frequencies, or the red end of the spectrum, as the source of light and the observer move away from each other reflex

an involuntary movement in response to a stimulus

refracted ray

a ray of light that has bent as a result of light speeding up or slowing down refraction the bending of light as a result of light speeding up or slowing down

an association between two or more variables; observed when a change in one variable causes a change in another relative dating a method of determining the age of an object relative to events that occurred before and after reliable

consistency of a measurement, test or experiment repeatable

the same results and observations can be made under the same conditions and using the same method reproducible

the ability to repeat and replicate a test exactly

resistance a measure of how difficult it is for the charged particles in an electric circuit to move

resistor

a device that has opposition to an electric current resource

any natural material that can be extracted and used

response

the action or change in behaviour or physiology that occurs as a result of a stimulus retina

light-sensitive cells that convert light into electrical signals

retinal cell

a photoreceptor cell of the eye’s retina rhizome

a horizontal, underground stem that grows parallel to the soil surface; serves both as a storage organ and as a means of vegetative reproduction risk assessment

the determination of quantitative or qualitative estimate of risk related to a well-defined situation and a recognised threat (also called hazard)

risk

the potential for harm

RNA

(ribonucleic acid) a single-stranded molecule essential for protein synthesis; contains the sugar ribose, unlike DNA which has deoxyribose runner

specialised horizontal stems that grow along the ground’s surface; they extend from the main plant and can produce new plants at their nodes

Ssafety data sheet (SDS)

a document providing information about how to minimise the risk associated with the use, handling and storage of hazardous chemicals

sampling bias

a bias where a group of test subjects does not represent the larger sample group

Sankey diagram

a flow chart that represents movement or change in resources, such as the transfer or transformation of energy satellite any object that orbits a planet or a star scalar quantity quantity that has magnitude (size)

scatter graph a graph used to represent continuous data; it consists of discrete data points scattering of light when light waves strike particles such as dust, gases or water droplets, causing them to deflect from their original path in different directions scientific argument an explanation based on evidence rather than belief or opinion scientific scepticism questioning the scientific basis of claims, theories or beliefs scrotum

a sac-like structure that contains the testes

sebum

selective gathering

the careful removal of specific plants or animals from a population to maintain ecological balance while allowing for resource use

self-pollination when both gametes come from the same plant

semiconductor

a material that has properties between conductors and insulators; its conductivity increases by adding some impurities to it

seminal vesicles

a pair of small pouch-like structures that provide a sugary fluid that assists sperm to travel along the vas deferens

sensory neuron

a nerve cell that carries a message from a receptor to the central nervous system; also known as an afferent neuron

series circuit

the positioning of loads (e.g. lights) side by side in an electric circuit so that the electrical energy passes through one load at a time

sex chromosome

a chromosome that determines the sex of an organism

sexual reproduction

the combination of genetic material from two parent organisms, resulting in offspring that are genetically unique

sexually dimorphic

describes species in which the male and female organisms look structurally different

shell diagram

a diagram that shows the number of electrons in each electron shell around a particular atomic nucleus

short circuit

a condition in an electrical circuit that allows the current to flow along an unintended path

social sustainability

practices that focus on inclusion, equity and just societies to ensure the wellbeing of current and future generations

solar energy

the energy from sunlight that can be converted into electrical or heat energy

solar radiation

radiant electromagnetic energy from the Sun

somatic cell

all types of cells in the body except for gametes (egg and sperm)

somatic nervous system

DRAFT

an oily secretion produced in the sebaceous glands of the skin secondary colours of light the colours of light (magenta, cyan and yellow) that result from the mixing of two primary colours of light secondary data data collected by someone else selection pressures

environmental factors that affect an organism’s ability to survive

silent mutation

a change in a DNA sequence that does not alter the amino acid sequence of a protein, typically having no impact on its structure or function

single displacement reaction

a reaction in which a more reactive element displaces a less reactive element on a molecule

sister chromatids

identical copies of a chromosome that are formed during DNA replication and are joined together at the centromere; they separate during cell division

the part of the nervous system that controls the muscles attached to the skeletal system

sonar

the recording of how long it takes a sound wave to reflect or echo back to its starting point after it hits an object; it is used to detect the location of things, for example, a submarine speciation

the process that results in the formation of a new species

species

a group of organisms that can breed with each other in natural conditions to produce offspring that are viable (alive) and fertile (able to have children of their own)

specific immune response

the response of the immune system that targets specific pathogens using B cells and T cells; also called the “adaptive immune response” spectroscope

a device that spreads out different wavelengths of light spectrum

a chart or graph that shows the intensity of emitted light across different wavelengths speed the distance travelled per unit of time speed of sound the speed at which a sound wave travels through a medium at a certain temperature

sperm

the male gamete (sex cell)

spinal cord

the cylindrical bundle of nerve fibres and associated tissue which is enclosed in the vertebrae

spore

a tiny reproductive structure that, unlike a gamete, does not need to fuse with another cell to form a new organism

spreadsheet

a digital tool that allows you to organise, calculate and analyse data displayed in rows and columns stamen

the male reproductive part of a flower, consisting of the anther and filament standard deviation measures how close the values in the data set are to the mean; a low standard deviation indicates data points are clustered tightly around the mean, while a high standard deviation means they are more dispersed

stellar fusion

is the process where light atomic nuclei fuse under extreme heat and pressure in stars, releasing energy

stem cell

a cell that can produce different types of cells; adult stem cells can produce a limited number of cell types (e.g. skin stem cells), whereas embryonic stem cells can produce many types of cells

steroid hormone

a cholesterol-based hormone that is slower acting and relatively long-lived stigma the top of the carpel; this is where the pollen from the anther begins its journey to the ovary stimulus

any information that the body receives that causes it to respond

stimulus–response model

a model that describes how an organism responds to a stimulus (change in their environment)

style

a slender, tube-like structure that connects the stigma to the ovary in the carpel subsidence

the gradual caving in or sinking of an area of land

substitution mutation a form of mutation where one nucleotide is substituted for another; may or may not result in a deformed protein

substrate

synaptic terminal

the bulb-like structure at the end of an axon that transmits information (neurotransmitters) to the synapse; also called an axon terminal synthesis

a reaction that involves building up compounds by combining simpler substances, usually elements

systematic error

a consistent and predictable difference in measurements

T

T cell

an immune cell that recognises and kills pathogens

target cell

a cell that has a receptor that matches a specific hormone

temporal relationship

the timing or order of events in relation to each other

test cross

a genetic cross used to determine the genotype of an individual with a dominant phenotype; requires a cross with an individual that is homozygous recessive for the trait

testis

(plural: testes) the male reproductive organ that produces sperm

testosterone

a male hormone involved in the reproductive system

the Doppler effect the apparent change in the frequency of a wave when there is a relative motion between the source of the wave and the observer

thermoplastic polymer

a polymer that softens and forms new shapes when heated

thermoreceptor

transcription

the process of copying the DNA that makes up a gene to mRNA transformed describes energy that has changed into a different form transgenesis

the process of introducing a gene from one species into the DNA of another species, creating a genetically modified organism (GMO)

transgenic organism

an organism that has a gene from another organism inserted into its own chromosomes

DRAFT

a nerve cell that detects temperature thermosetting polymer

a polymer that does not melt or change shape when heated

transitional fossil

a fossil or an organism that shows an intermediate state between an ancestral form and its descendants; also known as a “missing link”

translation

the formation of a protein from RNA; occurs on a ribosome

translucent

a substance that allows light through, but diffuses it so that objects cannot be seen clearly

transparent

a material or object that you can see through; allows light to pass through transverse wave

a type of wave where the vibrations are at right angles to the direction of the wave

trend

the general tendency of a set of data to move in a certain direction trisomy

a genetic condition characterised by the presence of an extra chromosome in an individual’s cells, resulting in a total of three copies of a particular chromosome instead of the usual two tRNA

a molecule that carries amino acids

true value

the value that would be obtained if its measurement was free of errors true-breeding

a molecule that reacts with an enzyme sustainability to maintain, manage and minimise damage to resources so they are available for future generations, while meeting the needs of the present synapse

a small gap between two neurons, across which nerve impulses are transmitted

total internal reflection when a light ray passes from a more dense material at an angle larger than the critical angle, it can be reflected back into the dense medium

trace fossil

a geological record of biological activity, distinct from body fossils; includes footprints, burrows, nests, fossilised dung and bite marks

an organism known to be homozygous dominant or homozygous recessive

tuber

the swollen, fleshy storage organ of a plant that develops from underground stems; serves as a storage organ and a means of vegetative reproduction

turbine

a large wheel with angled sections called vanes, like a propeller, that is used to generate electricity

U

ultrasound

a high-frequency sound, with a frequency above the range humans can hear

unbiased

showing no prejudice for or against something

uncertainty

the range of possible values where the true measurement lies

underground mining

a method that creates tunnels to reach and extract deeper minerals

unicellular prokaryotic organism

a single-celled life form without a defined nucleus or membranebound organelles, including bacteria and archaea

univariate data

data about a single variable universal indicator

a solution that is used to determine the pH (amount of acid or base) of a solution

upwelling

a process in which deep, nutrientrich cold water moves up towards the surface

uterus

an organ in the female reproductive system; where the foetus develops

Vvaccination

an injection of an inactive or artificial pathogen that results in the individual becoming immune to a particular disease

vagina

a female reproductive organ; a muscular tube connecting the outside of the female body to the cervix

valence electrons

the electrons in the valency shell of an atom

valence shell

vas deferens

the tube through which sperm travel from the epididymis to the prostate

vector

an organism that transmits a pathogen to a different species

vector quantity

quantity that has size and direction (e.g. velocity, displacement)

vegetative reproduction

asexual reproduction in plants from vegetative parts like roots or stems; examples include runners, tubers and rhizomes

velocity

the vector quantity that measures speed in a particular direction

vestigial structure

a structure in an organism that no longer has an obvious purpose

virtual focus

the point from which the rays of light seem to come

virtual image

an image that appears in a mirror; it cannot be captured on a screen virtue ethics

an ethical framework focused on the character of the individual(s) making the decision

visible spectrum

the variety of colours or wavelengths of light that can be seen by the human eye

voltage

a measure of the amount of energy in joules given to a unit of charged particles passing through a battery

Wwater cycle

the continuous movement of water on, above and below the surface of Earth

watt

unit of power; 1 watt is equal to 1 joule per second

wet cell contains wet substances and uses a chemical reaction to produce electrical energy (e.g. a car battery)

white blood cell an immune cell that destroys pathogens

X-linked dominant

an inheritance pattern in which a gene associated with a trait or disorder is located on the X chromosome, and only one copy of the gene is needed for the trait to be expressed; both males and females can be affected

DRAFT

the outermost electron shell of an atom valency

the number of electrons an atom needs to lose, gain or share to have a full outer shell

valid

where a test investigates what it sets out to investigate

Van de Graaff generator

a machine that produces an electrostatic charge

wave

a disturbance that transfers energy through a medium or space without the transfer of matter

weaning the gradual transition of a young mammal from a milk-based diet to solid food, reducing reliance on maternal milk weather the temperature, humidity, rainfall and wind on particular days at a particular place

X-linked recessive

an inheritance pattern in which the gene causing the trait or disorder is located on the X chromosome and two copies of the gene are required for females (XX) to express the trait; in contrast, males (XY) will express the trait if they inherit a single copy

Zzoonotic a disease that can be transferred between non-human animals and humans

zygote

the first diploid cell of a new organism that results from the union of two haploid gametes during fertilisation

DRAFT