Physics and Chemistry 3 Student Book sample by Grupo Anaya, S.A.

DEMO

N O I T A C U D E Y R A D EC O N

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Building

Blocks

this is

your book

Reading and listening

ch unit

f ea The opening pages o

Speaking

We read and listen about the topic of the unit, learning about key concepts and developments in technology.

Force and its effects g

Reading and listenin

Understanding

A debate t. the following statemen and 14.3. Debate Follow the Analyse SDG 13.a to planet Earth.” are detrimental “Human beings ts instructions. group prepares argumen groups. Half of the the group prepares • Step 1: Form small t. The other half of statemen the that agree with ts. with the statemen arguments that disagree to make. ts that you want on the main argumen • Step 2: Decide ts and prepare argumen counter think about the • Step 3: Try to answers for them. debate. • Step 4: Hold the

heat our Burning fossil fuels to dioxide. homes creates carbon re This causes Earth’s temperatu to rise.

the forces of nature

. for their strength aren’t exactly known from one place to Human beings we move heavy objects However, every day than just the strength task that needs more another. This is a the of of our muscles. nding thanks to our understa This has been possible of nature. As a result, control the forces main elements that heavy objects easily. s that can move we have built machine is our intelligence. and Our real strength the face of our planet tion is changing it. We must find However, construc l activity are polluting industria Earth. from residues we want to protect these problems if ways to address text that mean... 1 Find words in the strong. being physically a) The quality of

know how That’s true But now we using the to generate electricity waves, power of the wind and planet. which doesn’t harm the

b) Weighs a lot. c) Work to do. l process. after an industria d) A substance left text. to summarise the of control the forces must learn to better a) Human beings more efficiently. to find nature to move objects this will help us are strong, and b) Human beings by pollution. caused s solutions to the problem nature but this has learned to control have beings c) Human nces. had negative conseque two and 11.3. Write ion on SDG 9.1 they Look for informat 3 ences of the changes negative consequ positive and two surface. cause on the Earth’s

Writing A short report 5 and 7 nt of between 17.1, an investme Development Based on goal the Sustainable required to reach nts reached billion dollars is international agreeme caused by research on the Objectives. Do repair the damage that is needed to findings. to raise the money to summarise your Write a short report lization. industria

sentence 2 Choose the best

SDG. Reflection on and analysis of SDGs, such as gender equality, climate action, reducing inequalities, etc.

GE BANK GE BANK LANGUA LANGUA BANK GE NK GE BANK GE BA LANGUA LANGUA LANGUA BANK 127 GE BANK GE NK GE BANK GE BA LANGUA LANGUA LANGUA LANGUA BANK GE BANK NK NGUAGE NGUA BA GE LA LA UA

LANG

Writing 126

The audios of each unit’s content are available at www.anayaeducacion.es

We speak about the different issues relating to the unit and the UN Sustainable Development Goals.

Speaking

We write a variety of different styles and types of text relating to the unit topic, sometimes relating them to the UN Sustainable Development Goals. By practising different styles of writing, we improve our writing skills we need.

content development Two types of activities:

ä 2.3 Nuclear power station

An energy transformation is produced in an electric power station: from primary energy (that which we find available in nature) to electrical energy. Afterwards, this is distributed by means of the power lines of the country to the different points of consumption.

When we talk of nuclear power stations, we are referring to nuclear fission power stations, in which uranium is normally used. This deals with a non-renewable source of energy. Uranium is a radioactive material. Its atoms are not stable and end up splitting (undergoing fission) forming other lighter atoms. In the process of fission, matter disappears, transforming into energy which is invested to heat water. The steam is conducted through pipes until the turbines of the generator move, producing electricity, as seen in the lower image.

As mentioned in a previous unit, this energy transformation is possible thanks to the alternator. From an energy perspective, what is done is transform mechanical energy (that of the turning of the alternator) into electrical energy. Therefore, the challenge of producing electrical energy involves looking for natural resources that could make the alternator turn. Several alternatives have been found to do this, and a type of electric power station stems from each one.

ä 2.2 Thermal power station Thermal power stations transform chemical energy, obtained from burning coal, oil or natural gas; and the energy released is invested in heating water until it boils. The steam is conducted through pipes to the turbines of the generator, connected to the alternator. When the steam at high pressures moves the turbines, these make the alternator turn and electrical energy is produced which travels through power lines, as seen in the image below.

Working with pictures

Understand, think, search… Activities to strengthen learning and relate knowledge. res. with pictu Working city a p your ca Develop and n o rvati for obse . n tio interpreta

Unit

This source of energy is non-renewable; coal and oil will end up being exhausted, and they cannot be regenerated as they need millions of years to do so. It is also pollutes, as the waste substances are released into the atmosphere. Carbon dioxide stands out among them, as it contributes to the rise in the greenhouse effect, and therefore to global warming.

In the image below, why do you think the smoke from the chimney is dark while that from the cooling tower is white?

Nuclear changes are very profitable from an energy perspective; with 1 g of uranium the same energy can be obtained as with 2 000 kg of oil, or around 3 000 kg of coal. One disadvantage of these power stations is that they produce radioactive waste, which must be kept carefully isolated as long as they are toxic to Matter is condensed energy. The amount of energy E that forms a piece of matter life. But the main risk is their enormous danger in the face of accidents. of mass m is determined by Einstein’s If something goes wrong it can cause a radioactive leak, such as what equation, E = m · c 2 where c is the speed happened in Chernobyl in 1986, with hundreds of thousands of people of light, (c = 3 · 108 m/s). 3.5 UM approximation 3 MOTION seriously affected and thousands of square kilometres of landä abandoned for decades until the radioactive contamination fell to tolerable levels. UM is the simplest type motion that can be studied. However, speed is Also, more recently, in Fukushima in 2011, although in this case, despiteconstant, which means motion is usually more complex. For not usually What similarities and differences the seriousness of the accident, there were less consequences. do uniform you see during betweena aroad thermal example, motion is not trip, when birds migrate, a nuclear or when water flows power down station a river. and The speed will almost always vary. fission However, we can think of it power as UM,station? obtain the average speed and get a good estimate. We can also divide the trajectory into smaller segments, to approximate each of them to UM.Transmission Study the following example.

Nuclear fission power station Containment structure

line

Cooling tower

Problems solved

Steam generator

Water 1 A vehicle starts moving at kilometre zero. It travels

Thermal power station

for 50 minutes at vCondenser 1 = 120 km/h. It later travels for 20 minutes at v2 = 90 km/h.

Reactor

a) Create a s–t graph for the vehicle. Generator

Cooling tower Transmission line

Condenser Steam

194

d) When will the vehicle pass the 120 km point?

b) The average speed is equal to the total distance travelled divided by the total time (speed = distance ÷ time): s2 – s0 130 km e . 111, 4 km/h vm = t = t + t = 5 1 1 2 h+ h 6 3 c) If the motion had been uniform, the s–t graph would be (red line):

Transformer

140

Transformer

to transport it via the high-tension lines. The cooling tower, together with the condenser, cools the water. Find a resource on the production of electrical energy on anayaeducacion.es.

s = s + v · t = 0 + 120

h = 100 km

0 1 1 6 h Solutions to all the 1numeric activities are on anayaeducacion.es.

And the second segment goes from position s1 = 100 km to: s2 = s1 + v2 · t2 = 100 km + 90

km 1 · h = 130 km 3 h

s/km 140

120

20 0 10

t/min

Fireworks shows are a good place to compare the speed of light and sound. We can see the fireworks before we can hear them. If a firework explodes 500 m away from us, we will see the light 1.7 ms after the explosion. The light travels this distance one hundred and fifty times, faster than the time it takes to blink! However, we will hear the sound 1.5 seconds later (upper right picture).

Sound ts = 1.5 s Light tl = 1.7 · 10–3 s

The speed of sound is slower than the speed of light, which reaches us almost instantly.

Our universe is so big that we are unable to imagine it. We measure the distance between celestial bodies in light years (ly).

MILKY WAY

One light year is the distance light travels in one year. It is an enormous distance, equivalent to about 9.5 trillion kilometres! The star closest to the Sun, Alpha Centauri, is 4.2 ly away, and the North Star, Polaris, is 431 ly away.

Solar system

Problems solved 2 Galaxy M-31 is 2.5 million light years away and is 70

t/min

d) The 120 km point is reached in the second segment. We must therefore calculate motion for195 this segment: s = s1 + v2 · t 8 120 km = 100 km + 90

km ·t h

120 km – 100 km 2 = h = 13 min and 20 s t= 9 km 90 h To determine when the vehicle passes this point, we must add the time of the first segment:

120 km t= . 1, 077 h = 64 min and 37 s km 111, 4 h The estimated result is close to the true value.

Some natural phenomena move at a constant speed. For example, sound travels through air at approximately 340 m/s, and light travels through air at about 3 · 108 m/s. The speed of light is almost the same in air and in a vacuum. In fact, light travels so fast that it could travel around the Earth 7.5 times in just one second.

Our solar system is about two-thirds of the way out from the centre of the galaxy.

t = 50 min + 13 min + 20 s = 63 min and 20 s e) Using the equation: km s = v · t = 11, 4 · t = 120 km h

100

The icons included with some activities indicate the keys to the project.

men

Unit

ä 3.6 UM distribution

Our galaxy, the Milky Way, has an estimated diameter of approximately 150 000 ly. Our neighbouring galaxy, Andromeda (M-31), is 2.5 million light years away, and the most distant observable galaxies are 13 000 million light years away!

s/km

en 120 motion had been uniform? gm Se Advantages and disadvantages. Write aper list hour. of 5 The calorific value of 100coal depends on the type of coal. a) Give your answers in kilometres factors in favour of and against thermal power stations. Let’s imagine a type that gives off 30 000 kJ for each 80 5 1 Carry out the same task nuclear = h fission t1 = with 50 min ; t2 = power 20 min = h kilogram that it burns. Determine how many grams of 6 3 t1 60disintegrate in norder stations. matter would have to toUMobtain the e There are two consecutive UMs. Therefore, we will amount of energy. gm same e 40 S 4 Why do we not two take straight advantage of The gymsslope whereof the second draw lines. 20 people pedal online exercise to make alternator 6 theLook up information on how radioactive waste is shouldbikes be less steep an than the first because move? Think about thistravels idea at and writespeed. it would be isolated from nuclear0power stations. vehicle a lower possible to carry The it out. 10 20 30 40 50 60 first segment goes from position s = 0 to:

Fuel Alternator

c) Use the graph from section a) to draw a s–t graph Turbines that shows uniform motion.

e) Would it pass the 120 km at a different time if the Understand, think, search… Turbines

Generator

The steam moves the turbines of the generator. The electricity produced is transformed to the desired voltage

b) Calculate Steamthe average speed over the entire distance travelled.

Control rods

Water Boiler

The problems solved allow the learning of reasoning processes and problem-solving strategies.

Energy that forms matter

ä 2.1 Production of electrical energy

Working with pictures

2 ELECTRICAL POWER STATIONS

moving towards the Milky Way at about 300 km/s. a) How long will it take for its light to reach us? b) Give your answer (the distance) in SI.

c) Scientists believe that when both galaxies collide, a giant elliptical galaxy will be formed. When might this happen? a) Its light takes 2.5 million years. We see M-31 as it was that long ago.

b) In SI, the distance to the galaxy is: 15

9.5 · 10 m = 2.4 · 1022 m e = 2.5 · 106 al · 1 al c) The speed at which it is approaching the Milky Way is: km 103 m = 3 · 105 m/s v = 300 s · 1 km If this speed were maintained, it would arrive in: e 2.4 · 1022 m 16 9 t= v = m = 8 · 10 s . 2.5 · 10 years 3 · 105 s

Understand, think, search… 14 Determine the distance to the Sun if its light takes approximately 8 minutes 20 seconds to reach Earth.

15 How far away is a lightning bolt if we timed 2.5 s from the moment when we see the lightning until we hear the thunder?

16 The star known as Vega is 25.05 ly from Earth. If we could travel at 1 % of the speed of light, how long would we take to get there?

17 The centre of our galaxy is approximately 2.6 · 1017 km away. Express this distance in ly. How long does it take for light to reach Earth from the centre of our galaxy?

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134

KEYS

PROJECT

SDG

SDG Commitment Discover the Sustainable Development Goals and be an active part of our commitment to make a more equal and liveable world.

Developing thinking Work on strategies for thinking: reflect on the content you are learning, generate ideas, organise them, debate them, explain them…

Cooperative learning Get involved in your learning and participate in the group’s learning; you will find that cooperating improves performance and harmony in the class.

Emotional education Get to know yourself; identify the situations that bring up complicated emotions and manage them with constructive, self-affirming experiences.

A research project in each unit to implement the application of the scientific method and encourage the acquisition of skills and attitudes necessary for scientific work.

Science workshop SCIENCE WORKSHO

Unit

research project Introduction

the energy of the atmosphere

proof of the atmospheric pressure

You might think that global warming as a consequence of climate change and the growing number of highly devastating hurricanes and storms are opposite phenomena. This is because warming is associated with drought and desertification and in theory this is the opposite of torrential rain phenomena.

Glossary

Approaching the problem The presence of the atmosphere explains many everyday situations, but we do not notice it. This is because we live at the bottom of this great mass of air and do not have proven experience of the lack of atmosphere.

With this simple experiment we intend to explain the behaviour of the gaseous state compared to the temperature.

Objectives

1. MATTER. GASES

Nuclides

Force exerted on the walls of a container per unit of area due to collisions of particles in a gaseous state.

Kinetic-molecular theory

Theory that describes the different states of matter based on the kinetic energy of the particles of a substance (firstly described considering the gaseous state).

4. IDEAL GAS LAWS

Radionuclides

2. ATOMS BOND

Absolute zero

The theoretical temperature at which a substance would not occupy a volume and would not exert any pressure.

Chemical bond

Boyle and Mariotte’s Law

At a constant temperature, the volume of a gas is inversely proportional to the pressure that it exerts on the walls of the container in which it is found.

Octet rule

Charles and Gay-Lussac Laws

For a specific mass of a gas, both the pressure and the volume of the gas are directly proportional to the temperature.

40W

30W

20W

10W

2. THE ATOM 2. FROM THE ELECTRICAL NATURE OF MATTER TO THE FIRST ATOMIC MODEL

Path of hurricane Ophelia, which hit The dynamic between storms and warming seas occurs in part Ireland Process in mid-October Global involving2017. forces of attraction through more elements create a climate system: becausewhich of thetwo roleorthat hurricanes play in our warming cansubstance. affect hurricanes leading new they rebalance Earth's heat. The storms remove heat from tropical them to appear where they do not usually oceans in theeight form electrons of moisture the heat up into the When two they tend to accommodate in and theirpump last shell, occur. (Research andatoms Science.bond, November atmosphere. Hereprovides it is redistributed and radiated out into space. 2017). except H, Li and Be which are left with two electrons. This them with chemical

Molecular mass

The mass of the molecule of a substance.

Ions with a positive charge

Electrification

Process through which matter acquires a negative charge.

Aqueous reaction

Electron

Subatomic particle with a negative charge.

Artificial reaction

1. CHANGES IN THE COMPOSITION OF SUBSTANCES 1 With your classmates, and based

Decomposition reaction

3. FROM RADIOACTIVITY TO THE NUCLEAR MODEL OF THE ATOM

In vivo reaction

Alpha radiation

Type of radioactive emission where alpha particles are emitted from an atom. Alpha particles are composed of two protons and two neutrons.

Beta radiation

Type of radioactive emission where beta particles are emitted from the nucleus of an atom. Beta particles can be positive or negative.

Product

Gamma rays

Electromagnetic radiation that is originated due to radioactive decay.

Reagent

Golf Foil experiment

Experiment that gave insights on the shape of the atom.

Radioactivity

The lost of energy in the form of radiation from an unstable nucleus.

Natural reaction

on Chemical the work you have done, think reactions taking place within a solution in which the solvent is water. Results about the impact that these Chemical reaction provoked by humans. Include a description of the process needed to make the poster: extreme weather phenomena Chemical reaction where a single reagent products. have on the daily life of people • List becomes of websitestwo used to look up information. who live in areas of the planet that Chemical reactions taking place within organic of matter organs, cells, etc.). • Planning tasks (organisms, and people responsible. experience them.

Reaction

Synthesis reaction

Empirical laws

Visual Arts

C REATE

Working with pictures

Draw a waterfall from a high tank, and indicate which form of energy the water has at different points of the fall.

Number of protons in the nucleus of an atom of an element.

Mass number, A

It is the sum of protons and neutrons of an atom of an element.

5. FORCE AND ITS EFFECTS

Atomic orbital

Regions where electrons revolve around the nucleus.

Scalar quantity

Physical quantity defined through magnitude. The value is followed by its unit.

Electron shells

Energy level of orbits surrounding the nucleus.

Vector quantity

Valence electrons

It refers to electrons from the last shell of an atom.

Physical quantity defined through magnitude and direction. The value of the vector is proportional to its length and followed by its unit.

211

ä 2.7 Marine power stations The mechanical energy from seawater is harnessed in these power stations. Wave energy is that which harnesses the energy transported by sea waves (upper-right image). No method has been established to extract this energy, and nowadays there are different ways to do so.

This type of power station uses a renewable source of energy, as the potential energy of water is used. It does not produce pollution, but the required flooding of areas modifies the environment, consequently destroying entire ecosystems.

The other energy we can harness from oceans is tidal, generated by the movement of masses of water in tides. To do this, we need to find bays which flood in each high tide. Here a barrage* is built and the energy produced by water passes through holes with a turbine in each one of them, transmitting the movement to an alternator.

In some places that have hot springs, such as Iceland, they use it to carry the water to homes. In this way they do not have to heat water and save. There are also countries that use the high temperatures of the subsoil to create a closed circuit of water which is injected from the surface to the hot source, obtaining steam which rises and which will move the turbines of the generator.

Energy from water and wind Wind power station Rotor

ORGANISING MY MIND

This deals with a renewable source of energy, as the fuel is regenerated more quickly than it is consumed; however, it produces polluting gases.

Drives

There is no one standard design of device to collect wave energy. Look up information on the main methods that are used and draw a diagram of each one. The compare advantages and disadvantages.

Which countries have geothermal power stations? In which areas of the planet can we find them? Do you think they could be used in Spain? Look up information on this matter.

Dam Transformer

Alternator Transformer Generator

Turbine

The water moves the blades of the turbine of the generator.

Geothermal power station

c) Person B pulls perpendicularly to person A.

12 The following situation represents the forces that three people exert on a rock. Calculate the net force.

F2 = 500 N

can produce

F1 = 700 N can be

Cold water

Hot water

.................................

at-a-distance

.................................

for example

some can be measured by

friction

.................................

F3 = 300 N

Hooke’s law

change in the state of motion

1. Elastic limit

Systemic diagram, etc…

Circle of viewpoints. According to the characteristics of our country, what type of renewable energy would seem more logical to you to invest in? Make a list of the reasons that support your suggestion, and get ready to defend it in front of other classmates who have chosen an option different from yours.

1 Identify at least four common forces in your everyday life and say whether they are contact or at-a-distance forces. 2 Pick a body from your surroundings with more than one force acting on it. Draw the force diagram and net force in your notebook.

In accordance with goal 15.5, another type of wind turbine has been designed which would avoid killing birds. Look up how these new wind turbines are in the development stage and write a short report describing them.

3 Describe a situation in which a force causes a clear deformation and a change in the state of motion. 4 Can a body move without forces acting on it? Explain your answer.

12 Although we live on a planet where its surface is three

5 Two people exert forces on the same body, the first exerts 150 N to the south, and the second 200 N to the west. What is the net force?

quarters water, this source of energy is not used very often. Look for information on the Internet and draw up a list of the countries that are using tidal energy.

6 In the previous activity, what force would a third person have to exert in order for the net force to be zero?

197

144

Create In this section we create a cross-curricular project that joins Physics and Chemistry with other subjects.

3. Breaking point

Deformation is measured with

position

measures changes in

19 An elastic band, A, has an elastic constant of 50 N/dm, and another, B, has an elastic constant of 6 N/cm. Which band will offer more resistance to being deformed? Explain your answer.

.................

Deformations

.................

7 Propose three examples of plastic materials, and another three elastic materials.

Trust in your skills and knowledge, develop creativity, adapt to changing situations and have a proactive and responsible attitude.

2 Draw the forces that act on a vehicle that is moving along on a horizontal segment on a motorway with a constant speed. What is the net force?

18 The graph represents the elastic force of a spring compared to its deformation. Based on the graph, determine the elastic constant of the spring and explain what happens after point 1.

2. Permanent deformation

Look up all the objectives goals regarding goal 7 “Affordable and non-polluting energy” on anayaeducacion.es.

Enterprising culture

b) Person B pulls in the same direction as person A, but in the opposite sense.

Force

Forces

The wind moves the blades of the wind turbine.

196

Unit

The source of energy is the thermal energy from hot sources of the subsoil.

Round table. Work in groups and look for information to find out the current status of research on fusion power stations: where they are being located, what date we expect to have them available and their benefits. Show your findings on a wall.

The experiences of the Practical Work section to remember and apply what was studied in the initial unit of the book and, at the same time, work on the contents developed in the unit.

Systemic diagram

Visual organizer of the content

Organic waste, such as waste from forests, cattle, farming, etc. is utilised to produce a fuel which will be burned.

hands-on task you have just performed if air does not enter or exit because it is covered.

unit

1 Complete the conceptual map in your notebook. Following the example, make one with all the contents from the unit.

Brazil has opted for a model in which the waves move buoys fixed to mechanical arms.

Understand, think, search… Generator

Blade

2 Explain why the plastic bottle became deformed in the

REVIEW

barrage: a wall built across a river to store water

Hydroelectric power station

Sluice gate

from this resources to choose Remember o. for your portfoli

ä 2.9 Biomass thermal power station

F ocus on English

and the temperature? Describe it in terms of KMT and the corresponding empirical law.

review

Wave power station

ä 2.8 Geothermal power station

en to strength Activities d ie d u st n bee w h at h a s rk o ferent w using dif strategies.

A biomass power station is a thermal power station in which biomass is burned instead of fossil fuel.

Together with photovoltaic solar power stations, this is the great effort of renewable energy in Spain. It involves installing wind turbines in strategic zones, taking up large areas of land. Part of the kinetic energy of the wind moves the blades of the wind turbine. This movement makes the alternator turn, producing electric current (lower-right image).

1 What is the relationship between the volume of a gas

1. FORCES

In the first hydroelectric power stations, dammed water was left to fall in order to move the turbines of the generator; in current ones, it is pressurized through some pipes in the lower part of the dam (bottom-left image).

ä 2.6 Wind power station

• Carry out both experiments and find similarities and differences (if there are any).

Draw conclusions...

The mass of an atom of a specific element.

Atomic number, Z

ä 2.4 Hydroelectric power station

These two types of power station use renewable sources of energy.

• Observe the safety measures when handling hot elements.

Laws which come from the experimental studies, measurements and results.

Atomic mass

Unit

Look for and watch a video on homemade wind turbine generator to see how a wind turbine works. Then, create your own model.

Guidelines

Chemical reaction that take place in nature without the interaction of humans. • Difficulties in carrying out the task and how you overcame them. Substance substances) as aofresult of a chemical reaction. only involves (or droughts and anthat appears • Areas improvement. increase in temperatures? Process in which reagents rearrange to form new substances, called products. Discussion, conclusions and presenting your work 3 AreInitial the factors affected(or by climate substance substances) that reacts in a chemical change to generate new Use the poster you have prepared to include knowledge from Geography change interlinked? ones. relating to migrations; in this case due to climate change. Chemical reaction where two or more reagents become only one.

2 Can we claim that climate change

44 4. LAWS OF CHEMICAL COMBINATION AND CHEMICAL EQUATIONS

Do you think Physics and Chemistry and English have anything in common? Discover how language, physics and chemistry are linked so you can learn them all.

• Through the use of photovoltaic panels. Of all the electric power stations, the photovoltaic is the only one that does not use an alternator, as the photovoltaic panels have the property to produce electricity directly from the light they absorb.

Materials • Plastic bottle • Water • Ice • Tray. For the alternative suggestion, you will need: • Empty soft drink can • Container to heat water • Tray for cold water • Tongs to handle the can without the risk of burns.

4. CHEMICAL REACTIONS Final reflection

Ions with a negative charge

Focus on English

• A boiler with water heats up by means of large mirrors which focus light from the sun onto it until the water boils, and the steam redirected through pipes moves the turbines of the generator. This type of electric power station is the solar thermal power station.

C Alternatively, you can heat a soft drink can in a water bath to around 60 ºC and then, cool the can quickly by submerging it in cold water. Make sure water does not get inside! In this case, you will see how the volume suddenly contracts.

“Was the extreme hurricane season of 2017 driven by climate change?” In Research and Science, November 2017, adapted from an article by Annie Sneed/Scientific American

Sum of the masses of the atoms that are part of the formula of the substance.

210

In solar power stations, the electromagnetic energy coming from the sun is transformed into electrical energy by means of two mechanisms:

B Then, quickly cool down the bottle by placing it in a tray with ice and pouring cold water on it. See how the bottle changes shape.

“In some senses, hurricanes are a relief valve,” explains Kevin Trenberth, a scientist in the Climate Analysis Section at the National Center for Atmospheric Research of the United States.

stability.

Cation

6. ATOMIC ORBITALS

ä 2.5 Solar power station

Our proposal A Fill three quarters of a plastic bottle with hot water and put the lid on. You will therefore have a volume of air inside the bottle at a temperature higher than room temperature (one quarter of the bottle).

10E

Formula unit mass

Anion

4. THE NUCLEUS OF THE ATOM

2 ELECTRICAL POWER STATIONS

Your proposal The volume of a gas enclosed in a container is the same as the capacity of the container itself. If the container is deformable, its shape and capacity will depend on the value of the pressure inside and outside the container. Suggest different ways to show this.

3. CHEMICAL SUBSTANCES

5. CHEMICAL FORMULAS

We learn the relevant terms that are underlined in the units with a clear definition.

How can we prove that the volume of gas decreases if the temperature also decreases by using everyday materials?

Unstable atomic isotopes with an excess of energy which transform into other stable Shared reading Procedure nuclei, emitting radioactivity. Search for information on this phenomenon. You could use this extract as a starting point:

Tension

Glossary

Make a poster explaining the relationship between the sea temperature and the formation of hurricanes, using your knowledge from the unit. Do Variant of atoms with a specific number of protons andand neutrons. this work in groups, plan and share out tasks.

7. APPLICATIONS OF RADIOACTIVE ISOTOPES

2. KINETIC-MOLECULAR THEORY Gas pressure

practical work

measures changes in

8 Write two everyday phrases which correctly use the term “force” from a scientific point of view, and two other phrases which do not use this term correctly. 9 Indicate in which cases the state of motion of a car is changing, and in which it is not. Explain your answers. a) When it is going up a straight hill at 50 km/h. b) When it curves at a constant velocity of 80 km/h. c) When it starts to brake because the traffic light has turned red. d) While it is stopped at the traffic light. 10 In which cases from the previous exercise do the forces acting on the car cancel each other out? Explain your answer. 11 One person, A, pulls a big stone with 500 N to the right using a rope. If the other person, B, also ties a rope and pulls with 400 N, what will the net force be if: a) Person B pulls in the same direction and sense as person A. Solution to the numeric activities are on anayaeducacion.es.

Questions on the essential aspects of the unit so that you may make your own summary.

Academic and professional

13 Explain what it means for the elastic constant value of a spring to be 250 N/m. 14 If the spring in the previous activity is stretched with a force of 196 N, how far does it stretch? How much force would we need to pull on it in order to deform it by 5 cm? 15 We measure the deformation that a spring experiences based on the force applied to it, obtaining the following data: F/N

Δl/cm

Draw the graph showing the deformation over the force and determine for which values the spring could serve as a dynamometer. In this interval, what is the value of the elastic constant?

Explain in detail how you would build a dynamometer.

17 A 28 cm spring compresses until its length is 19 cm by applying a force of 27 N. a) Determine the spring’s elastic constant in SI units, and interpret its value. b) What will be the spring’s length when we stretch it with a force of 15 N?

20 A spring with an elastic constant of 10 N/cm joins with another of 20 N/cm. How much will they stretch as a whole if, with one fixed end, we pull from the other end with a force of 20 N? Explain your answer. Motion 21 A body’s position in a reference system can take positive or negative values, depending on whether it is to the right or left of the point of origin in the reference system, respectively. Of the other magnitudes we have studied (distance travelled, speed, acceleration), which can take positive or negative values, and which can’t? Explain your answer. 22 A woman goes to the hardware store and goes back home by the same route. The hardware store is 1.2 km from her home. It took 15 minutes to get there and 20 minutes to get back. How long did she spend at the shop, if the total average speed was 1 m/s? 23 Draw the distance-time graph for the previous activity assuming that the motion starts at the position s0 = 0. 24 It takes a small plane 2 hours and 18 minutes from the start of take-off until finishing its landing. If the average speed of the trip is 200 m/s, how far has it travelled? 145

Images to observe and interpret.

ICT

orientation

Evaluation

Linguistic Plan

Learn how to obtain information, select it and apply it; to plan, manage and work on projects; to collaborate online in an ethical and safe manner.

Evaluate your personal skills, discover and awaken your calling, train yourself to make decisions and learn to choose between different options.

Discover different strategies to analyse what you have learnt and how you learnt it; train yourself to take responsibility or overcome difficulties.

Use your communication skills in the different types of text that you will see. Language is always present, communicate!

The resource bank is LIKE THIS www.anayaeducacion.es A space with resources, techniques and activities, designed to strengthen your knowledge. Access the resource bank by registering at anayaeducacion.es. You just need to have an email, the code indicated on the first page of this book and the permission of a parent or a legal guardian.

More about the keys

Resources related to

THE KEYS of the project SDG

SDG Commitment, with microvideos that will help you know what are the targets for reaching the Sustainable Development Goals worked on in this project.

Linguistic Plan, with infographics that will give you models to work with the four linguistic skills, using different types of texts (descriptive, narrative, explanatory, etc.). Cooperative learning Preparing for the task In small groups, of four or five members: 1 All the members of the team will review how the assigned task can be accomplished. 2 To do this, the steps can be shared out to each team member who then in turn will explain how each part of the process can be done to the others. The others listen and participate if they think they can contribute something.

Authorship / adaptation : Variant of the Educational Innovation Laboratory of the colegio Ártica - David and Roger Johnson.

Developing thinking, where explanations are included on how to apply the different strategies for thinking proposed in the project.

3 Once everyone is in agreement on how to do each part, you will all complete the tasks and, finally, verify, among everyone, that you have solved it correctly.

Cooperative learning, which includes the description of the cooperative learning techniques proposed in the project. Emotional education, with resources to support you with overcoming worries generated in different situations in your learning process (beginning of the school year, taking a test, etc.).

Thinking techniques Logic Wheel This thinking technique will help you to establish phases when analysing specific content that you have to study.

Identify What is it? What is it like? Are there different types?

By following a logical sequence (the logic wheel), and by asking yourself a series of questions in each phase, you can:

• Identify content by asking yourself: What is it? What is it like? Are there different types? • Compare the content by formulating questions such as: In what way is it similar to ...? In what way is it different from ...? • Establish cause-effect relationships by asking yourself questions such as: Why? What impact does it have ...? • Argue, assess and ask yourself questions such as: What conclusions can be drawn after the analysis? What can be assessed or scored about it? Doing a data dump of these questions into a graphic organiser will help you. Authorship: Hernández, P., and García, L. A.; adapted by Escamilla, A.

Compare

Argue, assess What can we conclude?

Logic wheel

3 Establish cause-effect relationships Why? What impact does it have ...?

In what way is it similar to ...? In what way is it different from ...?

ICT, by using data sheets that will reinforce your healthy, correct and safe use of information and communication technologies.

Academic and professional orientation, with information on different professions linked to the subject content.

Evaluation, which includes resources for your portfolio, as well as rubrics and targets that will facilitate your self-evaluation.

NOTEWORTHY

resources in the material A utonomous-community specific contents W hat you should know T o study L earn by playing Virtual laboratories and simulations V ideos P resentations S elf-assessments S olutions

Resources classified

by unit

All the resources are classified so that you can easily locate the ones related with each section of your unit.

course contents Scientific Knowledge

Page 8

chemical substances

Page 72

The use of science ................................................................... 8 1. What is science? ................................................................... 10 2. Physics and Chemistry ....................................................... 13 3. Physical quantities. Units and measurements .......... 14 4. Measuring instruments. Errors ........................................ 16 5. Multiples and submultiples .............................................. 19 6. The language of science ................................................... 20 7. Laboratory equipment. Safety rules ............................. 22

The food industry ..................................................................... 72 1. Simple substances and compounds ............................. 74 2. Atoms bond ........................................................................... 76 3. Chemical bond ...................................................................... 78 4. Molecules and crystals ....................................................... 80 5. Chemical formulas ............................................................... 82 6. Industrial, biomedical and technological applications ............................................................................ 84

Research project. Archimedes and buoyancy ................................................... 24

Research project. Fertilizer explosives.................................. 86

Practical work. Does aluminum float in mercury? ....... 25

Review .......................................................................................... 88

Review .......................................................................................... 26

Appendix. Nomenclature ...................................................... 92

Matter. Gases

Page 30

Learning about gases ............................................................. 30 1. States of aggregation ........................................................ 32 2. Kinetic-molecular theory .................................................. 34 3. Changes in state ................................................................... 36 4. Ideal gas laws ........................................................................ 38 5. The Earth’s atmosphere .................................................... 42 Research project. The energy of the atmosphere ............................................ 44 Practical work. Proof of the atmospheric pressure .................................... 45 Review .......................................................................................... 46

Practical work. Simple substances and compounds ... 87

Chemical reactions

Page 106

Chemistry and global warming .......................................... 106 1. Changes in the composition of substances ............... 108 2. Atomic theory of chemical reactions ........................... 110 3. Chemical equations ............................................................ 112 4. Laws of chemical combination and chemical equations ................................................................................ 114 5. Amount of substance ......................................................... 116 6. Chemistry, environment and society ............................ 118 Research project. CO2 sinks .................................................. 120 Practical work. Chemical reactions with gaseous substances ................................................................................... 121 Review .......................................................................................... 122

the atom

Page 50

Scientific theory and paradigm shifts ............................. 50 1. First ideas about the atom ................................................ 52 2. From the electrical nature of matter to the first atomic model ......................................................................... 54 3. From radioactivity to the nuclear model of the atom .............................................................................................. 56 4. The nucleus of the atom .................................................... 58 5. Classification of the elements .......................................... 60 6. Atomic orbitals ...................................................................... 62 7. Applications of radioactive isotopes ............................. 64 Research project. Radioactive waste ..................................... 66

Force and its effects

Page 126

Understanding the forces of nature ................................. 126 1. Forces ....................................................................................... 128 2. Deformation ........................................................................... 130 3. Motion ...................................................................................... 132 4. Everyday forces .................................................................... 138 Research project. The acceleration of gravity ................................................... 142

Practical work. Chemistry of fireworks ............................. 67

Practical work. Elastic deformation .................................................................. 143

Review .......................................................................................... 68

Review .......................................................................................... 144

Nature of forces

Page 148

Geolocation ................................................................................ 148 1. Gravitational force ............................................................... 150 2. Electrostatic force ............................................................... 154 3. Magnetic force ...................................................................... 158 4. Electromagnetism ............................................................... 160 Research project. Magnetic force of an electromagnet ................................. 162

Energy sources

Page 190

Electric cars ................................................................................ 190 1. Rational use of energy ....................................................... 192 2. Electrical power stations .................................................. 194 3. Transport and distribution of electrical energy ....... 198 4. Electrical energy and power ........................................... 200 5. Electrical energy in our homes ....................................... 202 Research project. Types of lamps ..................................... 204

Practical work. Where is North? ......................................... 163

Practical work. Energy for cooking ................................... 205

Review .......................................................................................... 164

Review .......................................................................................... 206

Circuits

Annex Page 168

• Glossary ...................................................................................... 210

The transistor ............................................................................. 168 1. Electric current ..................................................................... 170 2. Electric circuit ....................................................................... 172 3. Ohm’s Law .............................................................................. 174 4. Kirchhoff’s Laws ................................................................... 176 5. Electric devices .................................................................... 180 6. Electronics .............................................................................. 182 Research project. Evolution of microprocessors .............................................. 184 Practical work. Measuring resistances ............................. 185 Review .......................................................................................... 186

CHEMICAL REACTIONS Reading and listening

Chemistry and global warming Chemistry is the scientific discipline that deals with chemical transformations; the change of substances from one to another resulting from reactions. As in many other fields of study, what forms the core of chemistry nowadays is the result of many years of research and practical work. Centuries ago, the predecessor of chemistry was alchemy, a non-scientific study of matter with different aims, for instance, finding the elixir of immortality. Although alchemy did not evolve, it set the basis that allowed asking relevant questions, thus igniting the development of the field. Research laboratories are places where cutting-edge chemistry takes place. Some objectives encompass developing techniques to enhance the efficiency of chemical reactions that accelerate or slow down industrial processes, studying reactions that take place in the environment, as well as designing specific reactions that could impact entire societies. Global warming could potentially jeopardise the existence of human beings, thus one of our biggest concerns. The origin of global warming takes place in the emission of considerable amounts of carbon dioxide to the atmosphere exceeding the limit that nature can absorb. A consequence of these emissions reflects on an increase in the average temperature of the planet. This situation has been taking place ever since industrial revolutions and has increased with the establishment and proliferation of industries all around the world.

1 What is the difference between alchemy and chemistry? 2 What is the main point of the introduction? 3 Find two synonyms to the word ‘jeopardise.’ 4 Name four different types of industries. Give an example of each.

106

Speaking An interview

Global warming and chemical reactions are not only affecting our atmosphere, the impact is also polluting our oceans. For this reason, SDG 14 focuses on ‘life below water.’ In pairs, imagine one person is a journalist and the other an expert on climate change. Use the following information to ask and answer questions on how people can conserve and sustainably use the world’s oceans, seas and marine resources. For open ocean and deep sea areas, sustainability can be achieved only through increased international cooperation to protect vulnerable habitats. Establishing comprehensive, effective and equitably managed systems of governmentprotected areas should be pursued to conserve biodiversity and ensure a sustainable future for the fishing industry. On a local level, we should make ocean-friendly choices when buying products or eating food derived from oceans and consume only what we need. Selecting certified products is a good place to start. Making small changes in our daily lives, like taking public transport and unplugging electronics saves energy. These actions reduce our carbon footprint, a factor that contributes to rising sea levels. We should eliminate plastic usage as much as possible and organize beach clean-ups. Most importantly, we can spread the message about how important marine life is and why we need to protect it. Source: https://www.un.org/sustainabledevelopment/wp-content/ uploads/2018/09/14.pdf

What can we do to take of our oceans and seas?

We can use less plastic. Writing An infographic

Based on the previous information and on deeper research, create an infographic to inform people on specific actions they can take to conserve and sustainably use the world’s oceans, seas and marine resources.

NK E BANK A B E G A ANGU LANGUAG L ANK ANK GE BANK B B E E G G A A U U GUA K LANG ANG N L A L AN GE BANK 107 ANK GE BANK B B E E G G A A U U G A LAN LANG LANGUA LANGU

1 CHANGES IN THE COMPOSITION OF SUBSTANCES

ä 1.1. Chemical changes As we have learned, there are changes in matter where substances do not change; in other words, no new substance appears. We call these physical changes. But there is another kind of change where some substances are transformed into different ones; we call these chemical changes: Chemical changes, also called chemical reactions, are those which cause new substances to appear. Therefore, we say a chemical reaction has taken place when: • The substances that were present before the change combine with each other and, partly, disappear. These substances are known as the reagents of the reaction. • Due to the combination of reagents, one or several new substances appear which were not present before the change. These substances are the products of the reaction.

A chemical reaction is any process where one or more substances are transformed into one or more substances. The reagents transform into the products.

ä 1.2 Diversity of chemical reactions There is an infinite number of chemical reactions and criteria to classify them; for example, depending on the number of reagents and products: if there is a single reagent which becomes two products, there is a decomposition reaction, and, on the contrary, if two or more reagents become one product, there is a synthesis reaction. Depending on the purpose of the reaction, it can be interesting to consider them as natural reactions, when no anthropogenic factors intervene; artificial reactions, if they occur due to human actions; reactions in aqueous solution, when substances are dissolved in water; or in vivo, reactions, such as those that take place inside cells.

Diversity of chemical reactions Glucose insulin

Insulin K+ ATP

Insulin Entrance of Ca2+

Mitochondria Ca2+

108

The synthesis of insulin takes place in the pancreatic cells. It is an in vivo reaction.

Photochemical smog, which causes atmospheric pollution in many cities, is a web of chemical reactions which are produced due to anthropogenic reasons.

Unit

ä 1.3 Evidence of chemical reactions At times, it is not obvious that a chemical change is taking place. Because physical changes might be taking place at the same time, it might not be easy to see the appearance of new substances. Some evidence of a chemical change is:

• Energy exchange between the substances which intervene in the chemical reaction and its environment. For instance, in the case of combustion reactions, this energy exchange is noticeable, but it is not so evident in all chemical reactions.

Evidence of a chemical reaction

When we notice the formation of bubbles in a glass of tap water, can we conclude that a gaseous substance has been produced as result of a chemical reaction?

1 Presence

or formation of a precipitate. If the reagents are in solution, it might be that the new substance obtained has a lower solubility, so it will precipitate and this may be observed at first sight.

As a result of a chemical reaction, we can obtain

Working with pictures

• Change in the properties of the environment where the reaction takes place. The properties of these new substances are different. For example, a precipitate (solid substance of low solubility) can form as a result of the chemical reaction, or bubbling may appear, if the new substance is a gas (in other words, of a boiling temperature lower than that of the environment).

2 Presence 1 2

Light and energy in the form of heat

or formation of substances in different state of aggregation. As in the previous case, if a gas is produced, a bubbling coming out of the solution will be observed.

3 A

change in colour. The appearance of a different colour in the reaction reveals the presence of a new substance.

Chemical 4

Substance of low solubility Gas

Substance of another colour

reactions that cause a great energy exchange are easily detectable, as it is the case of combustion, which exchanges energy in the form of light and heat.

Understand, think, search… 1

Graphic organiser. Chemical change has been defined as the opposite of physical change. But we have learned that some physical changes accompany a chemical change, although not all of them. Draw a Venn diagram to show this relationship between them. Explain your diagram to the rest of the class.

Check anayaeducacion.es for a resource on the evidence of chemical reactions.

I see, I think, I ask myself. When we take a jug of lemonade out of the fridge, we may notice the formation of a precipitate at the bottom of the jug. Can we conclude that a chemical reaction has taken place? Observe the evidence, and write the questions that occur to you to answer the activity.

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2 ATOMIC THEORY OF CHEMICAL REACTIONS

Not all substances react with each other when they come into contact. Some do so really quickly, others more slowly and others do not react. Furthermore, there are factors which influence whether a chemical change takes place or not and the rate at which it will happen. In this summary, we will learn the theory that explains, at an atomic scale, how chemical reactions happen and how quickly they do so.

ä 2.1 Collision theory According to Dalton’s atomic theory, a chemical reaction involves a reorganisation of atoms. In order to understand this process, we must keep in mind the ideas of the kinetic theory of matter, according to which matter is formed by particles (atoms, molecules or ions) which are in continuous movement. Due to this movement, particles crash into one another and, in appropriate conditions, the particles of the reagents move apart and regroup to form the products of the reaction. A chemical reaction takes place if the particles of the reagents crash into one another in an effective way, so that molecular bonds are broken which keep atoms together in the reagents, and new bonds are formed which give rise to products. For these collisions to be effective, two conditions must be fulfilled: • The collisions between particles must have enough energy. • The collisions must happen with the proper orientation.

Proper orientation of collisions Effective collision

Molecules get closer with enough energy and proper orientation.

An effective collision is produced.

New bonds are formed giving rise to the molecules of the products. Non-effective collision

Molecules get closer with enough energy but orientation is not proper. The collision is not effective. Molecules of products are not obtained, in other words, there is no chemical reaction.

110

Unit

Remember that…

ä 2.2 Factors that affect the reaction rate There are extremely fast chemical reactions, such as explosions, and other slower ones, such as the oxidation of iron. The rate of a chemical reaction is defined as the variation of the amounts of the products obtained, or of the reagents which disappear, per unit time. At times, the intention is to promote the formation of certain products that are beneficial to society, such as those obtained by the chemical industry; therefore, the rate of certain reactions is increased. However, in the case of non-desired reactions, such as food decomposition, the opposite effect is sought, that is to slow down the chemical change. In both cases, it is indispensable to know which factors influence the reaction rate. Some of them are: • Temperature. When temperature increases, the speed of particles increases, so the energy of the collisions that take place between them also increases, leading to a greater number of effective collisions and, accordingly, an increase in the reaction rate. When the temperature decreases, we get the opposite effect.

From now on, every time we talk about elementary entities, we will be referring to the smallest unit formed by a substance, which can be an atom, a molecule or a group of ions.

Working with pictures Besides temperature and concentration of reagents, there is another factor which affects the reaction rate: the presence of catalysts. Look up information on these substances and explain why they are so important. Give several examples and share your findings with the rest of the class.

• Concentration of reagents. In reactions that take place in solution, if the concentration of reagents increases, there will be a greater possibility of collisions between particles, and therefore, a faster reaction rate.

Factors which influence reaction rate

Food decomposition reactions are faster at room temperature (right) than inside cooled chambers (left).

The concentration of reagent in the reaction on the right is higher than that on the left, and therefore, the reaction rate is higher.

Understand, think, search… 3

Graphic organiser. Create an outline where you connect the ideas of the kinetic theory of matter and Dalton’s atomic theory with the collision theory of chemical reactions. Write conclusions on the factors which influence the rate of chemical reactions.

Think and share with a partner. Reflect and answer these questions: a) Do you think pressure affects the reaction rate if the reagents are gases? b) Will a log of wood burn before the same mass in the form of splinters?

At anayaeducacion.es, there is a resource on the formation of ammonia and another one about the oxidation of an apple.

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3 CHEMICAL EQUATIONS

A chemical equation is the symbolic representation of a chemical reaction which contains quantitative and qualitative information. Quantitative information refers to the number of elementary entities (atoms, molecules or ions) of reagents and products which intervene in the reaction. Qualitative information will be that which shows the state of aggregation of substances and the conditions in which the reaction takes place. A chemical equation is made up of: • Chemical formulas of the reagents separated by the ‘+’ sign, the symbol for chemical change (→8) and the formulas of products, also separated by the ‘+’ sign. • Stoichiometric coefficients, which indicate the number of particles of each substance that intervenes in the reaction. If the value of the coefficient is one unit, it is not written. To read the quantitative information that a chemical equation contains, it needs to be balanced. The number of atoms of each chemical element intervening in the process must be equal in both the reagents and the products. This is achieved by choosing the appropriate values for the stoichiometric coefficients, as shown in the charts on this page and the following one.

Balancing a chemical reaction We balance the reaction of iron sulphide (II) with oxygen to convert into iron oxide (III) and sulphur dioxide. Without changing the chemical formulas of both reagents and products, we follow these steps:

REAGENTS Iron sulphide(II)

The elements that only appear in one reagent and one product are chosen and we balance their stoichiometric coefficients. First, the metals and then the nonmetals:

Oxygen

PRODUCTS Iron oxide(III)

Sulphur dioxide

Then, we balance the simple substances, ending in H2 and O2. To do that, we count the number of atoms in the products and we balance the reagents:

Therefore, the stoichiometric coefficients are: 2 FeS + O2 8 Fe2O3 + SO2

2 FeS + O2 8 Fe2O3 + 2 SO2

To avoid fractional coefficients we multiply all the coefficients by the denominator of 2 · (2 FeS + 7 O2 8 Fe2O3 + 2 SO2) 2 the fraction, although both expressions are valid: REAGENTS

112

PRODUCTS

1 Ò 4 = 4 atoms Fe

2 Ò 2 = 4 atoms Fe

1 Ò 4 = 4 atoms S

2 Ò 7 = 14 atoms O

3 Ò 2 + 2 Ò 4 = 14 atoms O

2 FeS + 7 O2 8 Fe2O3 + 2 SO2 2

4 FeS + 7 O2 8 2 Fe2O3 + 4 SO2

Wo r k in g w it h p ic t u re s

Why do w e coefficients avoid fractional sto ichiometric in usefulininte chemical equation s? Are the rpretingth y eq contained in a chemic ualitativeinformatio n al equatio Look at th n? e figures on this pa these que ge to answ stions. er

Unit

Balancing a combustion reaction For this type of chemical reaction, we will always follow this method. We will use propane combustion as an example. In this chemical reaction, propane combines with oxygen to form carbon dioxide and water. The reagents and products of the reaction are: In order to know the number of molecules of carbon dioxide, we take into account that all the carbon atoms of propane will end up forming part of carbon dioxide.

REAGENTS

Propane

Oxygen

The number of water molecules is determined by the number of hydrogen atoms of propane, which is eight. Therefore, four water molecules are produced.

PRODUCTS

Carbon dioxide

Water

Lastly, there are ten oxygen atoms in the products; therefore, there will be five oxygen molecules in the reagents.

Following this reasoning, we establish the stoichiometric coefficients: C3H8 + O2 8 3 CO2 + H2O

REAGENTS

C3H8 + O2 8 3 CO2 + 4 H2O

PRODUCTS

3 Ò 1 = 3 atoms C

1 Ò 3 = 3 atoms C

2 Ò 5 = 10 atoms O

2 Ò 3 + 1 Ò 4 = 10 atoms O

8 Ò 1 = 8 atoms H

2 Ò 4 = 8 atoms H

C3H8 + 5 O2 8 3 CO2 + 4 H2O

ere n.es th al io c a c u ayaed cing chemic On an n la a pane b urce on pro o r s e e h r t o an is a ns and equatio ion. st combu

Understand, think, search… 5 Write the chemical equation that corresponds to the

a) b) c) d)

following description: Three dihydrogen molecules combine with one dinitrogen molecule to give two ammonia molecules’.

6 Indicate whether the following chemical equations are balanced or not. Correct as necessary:

8 Balance the following chemical equations: a) Ca + H2O 8 Ca(OH)2 + H2 b) Fe (s) + HCl (aq) 8 FeCl3 + H2 (g) c) CH4 (g) + O2 (g) 8 CO2 (g) + H2O (g)

a) 4 NH3 + 6 O2 8 4 NO2 + 6 H2O b) 2 K + 3 H2O 8 2 KOH + 3 H2 c) 4 KMnO4 8 2 K2O + 4 MnO + 5 O2 d) Na2O (s) + H2O (l ) 8 2 NaOH (aq)

7 Which one of these chemical equations corresponds

to the reaction of nickel (II) chloride NiCl2, with sodium hydroxide, NaOH? Solutions for all the numeric activities at anayaeducacion.es.

NiCl2 + NaOH 8 Ni(OH)2 + NaCl NiCl2 +2 NaOH 8 Ni(OH)2 + 2 NaCl NiCl2 + Na2(OH)2 8 Ni(OH)2 + Na2Cl2 2 NiCl2 + NaOH 8 2 Ni(OH)2 + NaCl

Glucose fermentation is a type of decomposition reaction; glucose breaks down into ethanol and carbon dioxide. Look up the formula of the three compounds, write down the reaction that takes place and balance it. Compare your solution with the rest of the class.

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4 LAWS OF CHEMICAL COMBINATION AND CHEMICAL EQUATIONS

Between 1789 and 1804, the laws of chemical combination were published with empirical laws that establish relationships between the mass of the reagents and of the products in a chemical reaction.

ä 4.1 Law of conservation of mass In 1789, the French scientist A. Lavoisier reached the conclusion that, in a chemical reaction, mass is neither created nor destroyed; only a transformation of substances takes place. This observation can be stated in the following way: In a chemical reaction, the sum of the masses of the reagents is equal to the sum of the masses of the products. The atomic theory explains this empirical law, since a chemical reaction is only a reorganisation of atoms. No new atoms are created; the atoms of the reagents are organised in a different way to form other substances, the products of the chemical reaction. Thus, the total mass of the reagents will be equal to the total mass of the products (Part 1 of the chart on the next page).

ä 4.2 Law of definite proportions Between 1794 and 1804, J. L. Proust established that, when two or more simple substances react to form a compound, the proportion by mass of the simple substances that reacted always had to be the same. This was verified by changing the masses of reagents in succession and checking that their proportion always remained constant. In a chemical reaction, the proportion by mass of the reagents and the products is fixed and independent of the amount that reacts. We can explain this empirical law by taking these facts into account: • The composition of each chemical substance is constant and expressed in its chemical formula. • The average atomic mass is a characteristic of each chemical element. The mass of a compound is obtained from the mass of the elements which make it up. • The number of elementary entities of each substance that intervenes in the chemical reaction is constant and is expressed by means of the stoichiometric coefficients in the chemical equation. Review what is explained in Part 2 of the chart on the next page.

Understand, think, search… 10 Knowing the average atomic masses of hydrogen

12 In the combustion reactions of wood in a chimney, we

11 From your answer to the previous exercise, verify that

(1 u) and nitrogen (14 u), does the formation of ammonia (NH3) from dihydrogen (H2) and dinitrogen (N2) comply with the law of conservation of mass?

the law of definite proportions is satisfied if we know that 7.5 u of dihydrogen combine with 35 u of dinitrogen to obtain 42.5 u of ammonia.

114

obtain ashes. The mass of ashes is lower than the mass of burned wood. Why does this happen? Is the law of conservation of mass satisfied? Explain the meaning of ‘empirical law’ and ‘theory’. What is the difference between an empirical law and a theory? Give an example of each case to back your statement.

Unit

The laws of chemical combination and chemical equations With this example, we prove the relationship between the laws of chemical combination (law of conservation of mass and law

of definite proportions), and the information obtained from a chemical equation.

Ammonia (NH3) combines with oxygen (O2) to give nitrogen monoxide (NO) and water (H2O). Part 1

4 NH3 + 5 O2 8 4 NO + 6 H2O

Atomic mass

No. atoms in reagents

Balanced chemical equation.

No. atoms in products

14 u

4·1=4

4 · 3 = 12

6 · 2 =12

16 u

5 · 2 = 10

4 · 1 + 6 · 1 = 10

REAGENTS

We check that the chemical equation is balanced. We add the average atomic mass data, which will be necessary later on.

PRODUCTS

NH3

H2O

14 + 3 · 1 = 17 u

2 · 16 = 32 u

14 + 16 = 30 u

2 · 1 + 16 = 18 u

17 u · 4 = 68 u

32 u · 5 = 160 u

30 u · 4 = 120 u

18 u · 6 = 108 u

68 u + 160 u = 228 u

120 u + 108 u = 228 u

We calculate the molecular mass from the average atomic mass.

We calculate the mass of each substance in the reaction from its molecular mass and stoichiometric coefficient.

We check that the law of conservation of mass is satisfied.

Part 2 NH3

H2O

68 u

160 u

120 u

108 u

Proportion between reagents mNH3 mO2

68 160

From the molecular masses of the substances that intervene in the reaction, we calculate the proportion between them.

These proportions remain constant for any mass, therefore obeying the law of definite proportions.

Proportion between products

mNO

mH2O

120 108

10 9

Repeat the calculations from the equation:

Proportion between reagents and products mNH3 mNO

68 120

17 30

;

mNH3 mH O 2

68 108

mO2 160 4 = = ; m NO 120 3 27 17

;

mO2 mH2O

160 108

40 27

On anayaeducacion.es there is a resource on the laws of chemical combination.

2 NH3 +

5 O 8 2 NO + 3 H2O 2 2

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5 A chemical reaction does not take place between a few particles; the number that intervenes is enormous, therefore, it is not practical to use the atomic mass unit. For that reason, this will be quantified in a different way.

AMOUNT OF SUBSTANCE

ä 5.1 Amount of substance

Amount of substance and mass

The amount that measures the number of elementary entities of a substance is called amount of substance and its unit in the SI is the mole. The property of matter that represents the amount of substance is not mass, but the number of particles that make up a certain extent of substance. As the mass of these particles is so small, the number of entities that make them up, for example, a gram of any substance is enormous. Moreover, this number will be different from one substance to another, as the elementary entities that make them up have different masses.

The quantity of grapes and chickpeas is the same; however, the mass of that quantity is different, since the mass of a grape is different from that of a chickpea.

One mole contains exactly 6.022 140 76 · 1023 elementary entities. This figure is called Avogadro’s number, NA.

Mass of a mole

ä 5.2 Molar mass

The value of molar mass of a substance numerically matches the molecular mass, or the mass of the formula unit, of that substance. Molecular mass Substance or formula mass/u

To establish the relationship between the mass of a substance and the present amount of that substance, we use the molar mass. The molar mass, M, of a substance is the mass of one mole of that substance, in other words, the mass of 6.022 140 76 · 1023 elementary entities of said substance. Their units in the SI are kg/mol, although g/mol is used more often.

Molar mass/ (g/mol)

196.97

KCl

74.6

NO2

46.0

The molar mass enables calculations to be made at a macroscopic scale from combinations of units of atomic scale. The relationship between amount of substance, n, and molar mass, M, is as follows: n (mol) =

m (g) M (g/mol)

Mass, amount of substance and number of elementary entities For a mole of acetaldehyde (ethanal, C2H4O), we know that: M (C2H4O) = 12 · 2 + 1 · 4 + 16 · 1 = 44 g/mol 44 g of C2H4O

1 mole of C2H4O

6.022 · 1023 molecules

24 g of C

In 1 mol of C2H4O there is 2 mol of C

1.2044 · 1024 atoms C

Multiplying by M (g/mol)

116

Multiplying by NA

4 g of H

In 1 mol of C2H4O there is 4 mol of H

2.4088 · 1024 atoms H

16 g of O

In 1 mol of C2H4O there is 1 mol of O

6.022 · 1023 atoms O

On anayaeducacion.es there is a resource on the amount of substance quantity.

Unit

Chemical reactions and amount of substance Calculate the mass of water, expressed in grams, that is obtained if 204 g of ammonia (NH3) react completely with oxygen, according to the following reaction. Check that the law of conservation of mass is fulfilled.

To calculate the mass of chemical substances intervening in a reaction, we start by its molar mass and the amount of substance of each one of them. 4 NH3

5 O2

4 NO

DATA: Average atomic mass N H O

DATA: Molar mass

14 u 1u 16 u

N H O

REAGENTS NH3

H2O M (H2O) = 2 · 1 + 16 M (H2O) = 18 g/mol

4 mol

6 mol

m (g) n (mol) = g n Md mol

mNH3 = 17 g/mol · 4 mO2 = 32 g/mol · 5 mNH3 = 68 g mO2 = 160 g

mO2

The numerical value of the average atomic mass equals the value of the mass in grams of a mole of atoms (molar mass).

M (NO) = 14 + 16 M (NO) = 30 g/mol

5 mol

mNH3

14 g/mol 1 g/mol 16 g/mol

PRODUCTS

M (NH3) = 14 + 3 · 1 M (O2) = 2 · 16 M (NH3) = 17 g/mol M (O2) = 32 g/mol 4 mol

Balanced chemical equation.

6 H2O

mlNH3 mlO2

Stoichiometric coefficients indicate the proportion between reagents and products expressed in amount of substance.

g m (g) = n (mol) · M d mol n

mNO = 30 g/mol · 4 mNO = 120 g

mNH3 mO2

mlNH3 mlO2

mH2O = 18 g/mol · 6 mH2O = 108 g

mNH3 mO2

160 g O2

From the stoichiometric coefficients and the molar mass of each substance, we calculate the masses of each substance to be able to establish the proportion by mass.

mlNH3 mlO2

We apply the proportion by mass to calculate the masses of the remaining substances from the mass of ammonia.

Data: m'NH3 = 204 g 68 g NH3

We calculate the molar mass of substances from their average atomic masses.

Remember that these proportions always remain constant. =

204 g NH3

68 g NH3

mlO2

120 g NO

mlO2 = 480 g

204 g NH3

68 g NH3

mlNO

108 g H2O

mlNO = 360 g

204 g + 480 g = 684 g

204 g NH3 mlH2O

mlH2O = 324 g

360 g + 324 g = 684 g

We check that the law of conservation of mass is fulfilled.

Understand, think, search… 14 Calculate the amount of substance present in 350 g of the following substances:

a) Potassium chloride, KCl c) Sucrose, C12H22O11 b) Iron. d) Ozone, O3.

15 Given the following equation, without balancing: N2 (g) + H2 (g) 8 NH3 (g)

Give reasons for whether the following statements are true or false: a) 1 g of N2 reacts with 3 g of H2. b) 1 mole of N2 reacts with 1 mole of H2. c) 1 mole of N2 produces the same amount of NH3. d) 28 g of N2 react with 2 g of H2 to produce 50 g of NH3.

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6 CHEMISTRY, ENVIRONMENT AND SOCIETY

Chemistry has a great impact on people’s quality of life, as it provides knowledge about new substances with all kinds of applications and contributes to the search for solutions to severe environmental problems.

ä 6.1 Environmental problems Some of these problems take place in the atmosphere as a result of gas emissions in chemical reactions. Acid rain In some industrial areas, gases are emitted, such as sulphur oxides and nitrogen, which move through the atmosphere and react with the atmospheric water vapour giving rise to corrosive acids, such as sulphuric (H2SO4) and nitric (HNO3) acids. When this solution of gases in water precipitates in the form of rain (called acid rain), it has catastrophic effects. Besides destroying buildings and historical monuments in towns, it also has a harmful effect in the flora and fauna of forests, rivers and lakes. Anomalous greenhouse effect The presence of carbon dioxide, CO2, in the Earth’s atmosphere keeps the temperature in our planet within certain values which enable life as we know it. This phenomenon, explained in the figure below, is known as the greenhouse effect. In recent decades, the amount of CO2 present in the atmosphere has noticeably increased. This is because the carbon cycle has been altered by using oil and coal as sources of energy in chemical combustion reactions. This greater amount of CO2 means that infrared radiation is retained in excess, which in turn provokes an increase in the average temperature of the atmosphere shown, for instance, with an increase in the frequency and intensity of hurricanes and cyclones. These phenomena are part of what we call climate change, devastating effects on our planet.

The greenhouse effect Part of the radiation that reaches the Earth from the Sun is reflected and another part is absorbed; therefore, the Earth heats up and, in turn, emits infrared radiation, as a result of being at a specific temperature.

The Sun

Part of the solar radiation is reflected by the Earth and the atmosphere

Most infrared radiation is absorbed by the greenhouse gases

Atmosphere

Earth

118

Part of the solar radiation is absorbed by the Earth’s surface and it warms it

The Earth’s surface emits infrared radiation

Greenhouse gases, such as CO2, present in the atmosphere, absorb part of the infrared radiation emitted by the planet and keep this radiation from dissipating outwards, contributing in this way to keep the average temperature of the Earth stable. If the atmosphere did not exist, the Earth’s surface would reach very high temperatures during the day and would be too cold at night, making the existence of life impossible.

At anayaeducacion.es there is a resource on the importance of CO2 in the atmosphere.

Unit

Stratospheric and tropospheric ozone Ozone is a molecule that consists of three oxygen atoms, O3, and forms a layer at about 60 km above sea level in the stratosphere. Ozone absorbs a part of the solar radiation that is harmful to health, ultraviolet radiation. In this process, the ozone molecule breaks down into dioxygen, O2, and monoatomic oxygen, O. The special characteristic of this dissociation is that it is reversible, in other words, ozone can form itself again nearly at once. Therefore, stratospheric ozone makes up the ozone layer, which is kept intact despite ultraviolet radiation. In the last decades of the past century, a hole in the ozone layer was detected, caused by the presence in the stratosphere of certain gases from human activity: the CFCs. Currently, environmental legislation has set strong limits on the production and use of these gases, and the hole in the ozone layer has been considerably reversed. On the other hand, since the Industrial Revolution, the presence of ozone in the lowest layer of the atmosphere, the troposphere, has been observed. This comes as a result of the emissions of nitrogen oxides and volatile organic compounds from the industry and motor vehicles. This tropospheric ozone is a pollutant, harmful to health and the environment.

Effects of acid rain in a forest.

ä 6.2 Chemical industry One of the main goals of this industry is the transformation of raw matter into other products which, in turn, will be the raw matter for an infinity of processed products. The dimensions of our daily life that are influenced by the development of chemistry are numerous, from water purification to the most advanced materials which are part of electronic devices, to polymeric fabrics and materials, car bodies and many more.

Evolution of the ozone layer during 2019.

Understand, think, search… 16

Associative analysis. Besides limiting the use of CFCs, there is another reason behind the reduction of the hole in the ozone layer. Look up information and share it with the rest of the class. How could this situation be improved without harming the planet?

Explain the differences between tropospheric and stratospheric ozone. Are there any differences between one molecule and the other?

Explain why CO2 is necessary in our atmosphere. What are the effects of the anomalous greenhouse effect? Search how it relates to goal 13.1 and think of how it could be sorted. Which actions are being carried out at the moment?

Look up information about the chemical product used to purify water and its cost. Write up a report and include a conclusion on its use with goal 6.1.

20 The development of the chemical industry is

accompanied by high pollution levels of water, air and soil. Many companies have tried to reduce this negative effect for some time, but it is very difficult due to the high economic costs and the complex adaptation of infrastructures. Look up information about a company that has managed to adapt to the goals established by the UN. Which measures have they adopted? Do you think it was easy? In teams, design an action plan for any company that has not done this.

From what you have learned in the previous exercise, which university degrees and professional training could you study in order to work in the chemical industry?

119

SHOP SCIENCE WORK

Research project CO 2 SINKS

Introduction The increase in the amount of carbon dioxide in the atmosphere has a direct relationship with the increase in the average temperature of the planet. The most obvious and known cause of this increase in carbon dioxide emerges as a result of the combustion of oil and coal utilised in the transformation of chemical energy into electrical energy (goal 13.a). However, there are other causes linked to the increase in carbon dioxide in the atmosphere, such as the increase in the world population. 1. Could the air that human beings who inhabit this planet exhale in the breathing process influence this fact? Look up the most well-known causes of climate change. 2. Could chemical reactions be developed where CO2 was a reagent and thus reduce its presence in the atmosphere? 3. In which natural process is CO2 a reagent and not a product of the reaction? Could this be the case with industry?

Objective Coral reef in the ocean that serves as a natural CO2 sink.

Research the so-called CO2 sinks and draw conclusions.

Procedure

Puzzle

Divide the class in groups of three. Each person will research one of the following areas, trying to answer the corresponding questions. Use bibliographies and references provided by the teacher. • Area 1. Impact of overpopulation. What has been the trend in the number of inhabitants of the planet in the last two centuries? How are the population’s habits? What is the impact of overpopulation in climate change? Does it affect lifestyle? • Area 2. Artificial CO2 sinks. Can climate change be reversed? Is it enough to reduce the emissions of greenhouse gases? What are artificial CO2 sinks?

Presenting your work 1 There will be an exhibition in the school with the infographics of the work groups.

2 Organise a round table for each

area to explain the conclusions. All classmates will elect the members of the round table.

120

C&R. Each participant who follows the round tables will write an article which summarises the positions and conclusions drawn.

• Area 3. Autotrophic nutrition. Natural CO2 sinks. What is the carbon cycle? What is autotrophic nutrition? Which living beings carry it out? Are they considered carbon sinks? Is there any action to promote this way of eliminating carbon dioxide?

Discussion of results Meet the members in each group who have been researching the same area and share your answers to the questions. Then, write a report for your area.

Conclusions Lastly, create an infographic with the pros and cons of each area to address actions related to the SDGs you have been working on.

Unit

PRACTICAL WORK CHEMICAL REACTIONS WITH GASEOUS SUBSTANCES

Approaching the problem The presence of gas in a chemical reaction, such as a reagent or product, changes the pressure of the reacting mixture. The difference between this pressure and the atmospheric pressure makes it possible to have proof of the reaction. Your proposal Prepare the task We will carry out two chemical reactions, one where carbon dioxide is obtained as the product of the reaction [1] and another one in which this gas is one of the reagents of the reaction [2]. NaHCO3(aq) + CH3COOH(aq) 8 CO2(g) + NaCH3COO(aq) + H2O(l ) [1] Sodium bicarbonate

Acetic acid

Sodium acetate

CO2 (g) + 2 NaOH (aq) 8 Na2CO3 (aq) + H2O (l )

[2]

Figure out, how to carry out each one of the reactions so that the difference in pressure before and after the chemical change is obvious. Observe the list of materials we suggest. Laboratory equipment necessary perform the experiment.

Our proposal Pour the vinegar (which contains acetic acid) into the plastic bottle and introduce the sodium bicarbonate into the balloon. Carefully, cover the bottle with the balloon and pour the bicarbonate inside. Observe the increase in volume of the balloon. Next, remove the balloon and add the sodium hydroxide. Screw the bottle cap and shake it, to boost contact between the carbon dioxide and the sodium hydroxide which is dissolving in the water. Observe the change in shape of the bottle. Materials • One 1.5 L flexible plastic bottle • One balloon • Around 100 cm3 of 6° vinegar • 8 g of sodium bicarbonate • 7 g of sodium hydroxide flakes

Guidelines • The masses of reagents that we show in the method exceed the stoichiometric amounts to ensure an adequate reaction rate. • Alternatively, the bottle can remain open in the first reaction, without using the balloon, so that the carbon

dioxide produced fills the space in the bottle and comes out. • To ensure this gas has displaced all the air that was inside the bottle, you can introduce a lit match and observe how the flame goes out.

Draw conclusions... 1

1-2-4. Work with your team and answer the following questions:

c) What is the meaning of the symbols in brackets in the chemical equations on this page?

b) Which effect is observed in the bottle when the second reaction takes place? Why?

d) Part of the reagents has not reacted. How do we know this?

121

r to choose Remembe rtfolio. po ur for yo

m this resources fro

unit

REVIEW

ORGANISING MY ideas

Hierarchical concept map

1 Copy the concept map in your notebook, or into an app to prepare concept maps, and do the following: a) Fill in the missing words. b) Explain why the word ‘molecules’ always has an alternative name in the concept map. To do this, think about the type of substances which are not molecular. c) Include a new branch in the indicated place in the concept map (1) to show which kind of change a chemical change is in relation with the composition of matter. d) From the branch in the previous activity, include which ones are pieces of evidence that show a chemical change is taking place.

e) Include in the map, from the place indicated (2), which other symbols can be displayed in a chemical equation. f) From the law of conservation chart, indicate the mathematical way of expressing this law. g) Indicate the relationship between amount of substance and mass in your concept map. To do this, include a branch in the place you consider appropriate. h) Based on orientation, illustrate with a drawing, and include it in the map, an effective collision and another one which is not effective. i) Include in the concept map the constant that connects the number of elementary entities with the amount of substance expressed in mole.

Chemical reactions

are represented by means of

are

Equations ? .................................

(1)

obey

Changes

in which we find

Law of conservation ? .........................................

in which the

Law of ? .........................................

(2) Coefficients ? .................................

Molecules or ? .................................

Chemical formulas

which give us information about the

Reagents

Collide

Number of Molecules or ? ................................

with enough

with proper

Energy

Orientation

and

which are expressed in the unit of amount of substance

giving rise to

? ........................... Mole

122

Molecules or ? .................................

Solutions for all the numeric activities at anayaeducacion.es.

Unit

Changes in composition 1 What does it mean that the nature of matter is altered in a chemical change? Define in your own words the expression nature of matter. 2 When vinegar and bicarbonate come into contact with each other, a gas is released, carbon dioxide, and sodium acetate and water are formed: a) Indicate the reagents of the reaction. b) Indicate the number of products of this reaction. 3 Indicate whether the following statements are true or false and explain why: a) Energy is released in all chemical reactions. b) Chemical reactions only occur naturally in living organisms. c) In a chemical reaction, reagents and products can be in different states of aggregation. d) Chemical reactions which take place in nature create an environmental problem. 4 There are chemical reactions for which the main application is energetic, as a great amount of energy is released during their development. Give an example and explain which environmental problem is associated with them.

c) From the previous chart, indicate in which time interval the rate of the chemical reaction is greatest. What do you base your answer on? Connect this observation with the collision theory.

The image. Explain what this represents:

What similarities and differences are there between the previous representation and the following one?

9 How does temperature affect the rate of a chemical reaction? Use the collision theory and kineticmolecular theory on the temperature and the average kinetic energy of particles. Representation of chemical reactions

Atomic theory of chemical reactions 5 Do all collisions that take place between the reagent particles cause them to break? Which factors does a collision depend on to be effective? 6 Is collision theory compatible with the law of conservation of mass? Both of them explain certain aspects of the chemical reactions, but do they make use of the same scale? Explain your answers. 7 The following table displays the masses of two substances while a chemical reaction takes place over time: Mass A/g

7,5

3,75

2,5

1,88

Mass B/g

1,7

3,4

6,8

13,6

Time/min

a) Are substances A and B, reagents or products of the reaction? Justify your answer. b) Graph the data of mass against time, and indicate if this is a linear relationship.

10 One student balances this chemical equation: NO + O2 8 NO2 as follows: NO + O2 8 NO3 Is what he has done right? Why?

11 Balance the following chemical reactions: a) Al + O2 8 Al2O3 c) NH3 + H2SO4 8 (NH4)2SO4 b) SO2 + O2 8 SO3 d) Fe2O3 + H2 8 Fe + H2O 12 Write all the information you can obtain from the following balanced chemical equation: 3 Cl2 (g) + 2 Fe (s) 8 2 FeCl3 (s)

13 Use this table to verify that the reaction in the previous exercise is balanced. Element

Atoms in reagents

Atoms in products

Cl Fe

123

REVIEW 14 Write the balanced chemical equation from the information in this drawing, where red has been used for oxygen atoms, black for carbon atoms and white for hydrogen atoms.

19 When we heat up 50 g of calcium carbonate, 28 g of calcium oxide and carbon dioxide is formed. a) Which mass of carbon dioxide is formed? b) If we start from 150 g of reagent, which mass is obtained from each product?

20 From the previous exercise, obtain the proportion by mass at which calcium carbonate and calcium oxide react. Could we obtain 56 g of calcium oxide from 60 g of calcium carbonate? Which law have you based your answer to this activity on? 15 Iron disulphide, solid, combines with dioxygen and sulphur dioxide and diiron trioxide, solid, are obtained. Write the balanced chemical equation of this process, indicating the state of aggregation of all substances. 16 Calculate the total number of atoms of each element in the reagents and in the products of the following chemical equations: a) 2 KOH + H2CO3 8 K2CO3 + 2 H2O b) 2 C2H6 + 7 O2 8 4 CO2 + 6 H2O

17 Check that the following chemical reactions are well balanced. If they are not, correct them: a) Zn (s) + Ag2O (s) 8 2 ZnO (s) + Ag (s)

we use 531.75 g of chlorine and 300 g of iron. Are these amounts in stoichiometric ratio? Use the information from the table. Mass of reagents/g

Mass of products/g

Cl2

FeCl3

212.7

111.7

324.4

Amount of substance 22 Fill in the following table:

b) 2 NH4NO3 (s) 8 2 N2 (g) + H2O (g) + O2 (g) c) MgSO3 (s) 8 MgO (s) + SO2 (g) d) H2S (g) + SO2 (g) 8 3 S (g) + H2O (g)

Substance

Mass/g

Water

Amount of substance/mol

Carbon dioxide

Total no. of O atoms 3.16 · 1024

Ozone

Laws of chemical combination and chemical equations

2.5

23 Order the following amounts from the lowest to the highest according to mass:

18 We have the following information about a chemical reaction:

a) 0.25 mol of lead tetrachloride.

3 H2 + N2 8 2 NH3

b) 5 mol of water.

Mass of products/g

NH3

6.06

28.02

34.08

c) 1 mol of sulphuric acid.

24 Calculate how many atoms and molecules there are in the following samples: a) 18 g of water.

a) Calculate the mass of ammonia that can be obtained if 7.878 g of hydrogen react completely.

b) 88 g of carbon dioxide.

b) Using the law of conservation of mass, calculate the mass of nitrogen required in the reaction based on the previous data. 124

3 Cl2 + 2 Fe 8 2 FeCl3

Calculate the mass of iron which will react and the mass of FeCl3 which forms.

c) 3 HCl + Al(OH)3 8 AlCl3 + 3 H2O

Mass of reagents/g

21 For the reaction of chlorine gas with iron:

c) 81 g of aluminium.

anayaeducacion.es Check the ‘Let’s study’ and ‘Learn by playing’ sections in the resource bank.

Unit

25 Silicon can be obtained from the reaction of SiO2 with coke (C) in an electric oven.

For this reason, fuels with lower carbon numbers are preferably being used. a) Balance the combustion reactions of methane (CH4), ethane (C2H6), propane (C3H8) and butane (C4H10):

a) Balance the chemical reaction:: + ___CO ___SiO ? ? 8 ___Si ? ? 2 + ___C 2 b) Which carbon mass reacts with 1 kg of SiO2?

I. ___CH ? ? 2 8 ___CO ? ? 2O 4 +___O 2 + ___H

Data: M (Si) = 28,09 g/mol; M (O) = 16 g/mol; M (C) = 12 g/mol.

II. ___C ? 2H6 + ___O ? 2 8 ___CO ? ? 2O 2 + ___H III. ___C ? 3H8 + ___O ? 2 8 ___CO ? ? 2O 2 + ___H

26 If we make potassium (K) react with water (H2O), potassium hydroxide (KOH) is formed and hydrogen gas (H2) is released.

IV. ___C ? 4H10 + ___O ? 2 8 ___CO ? ? 2O 2 + ___H b) One criterion to establish which one of the previous fuels is most polluting is to compare the amount of carbon dioxide released in the combustion of one mole of each one of them. Fill in the table with this information:

a) Write the balanced chemical equation. b) Calculate which mass of hydrogen gas is released in the previous reaction when 78 g of potassium react. c) If in the previous reaction, 20 g of potassium react with 9.21 g of water, what is the total amount of products obtained, in moles?

mole of CO2/mole of fuel methane ethane

Data: m (K) = 39 u; m (H) = 1 u.

27 Hydrochloric acid (HCl) combines with sodium hydroxide (NaOH) to give sodium chloride (NaCl) and water: a) Write and balance the chemical equation. b) To verify the law of conservation of mass is obeyed, calculate the mass of HCl needed for 103.5 g of NaOH to react completely. What masses of sodium chloride and water are produced?

28 An iron nail of 5 g is left out in the open. After some time, we see a part has oxidised, forming 5 g of diiron trioxide: a) What mass of iron has reacted? b) What mass of iron remains unreacted? Which percentage of the mass of the nail represents the part that has remained unreacted?

Chemistry and environment 29

Look up information on the destruction of the ozone layer and the anomalous greenhouse effect. Draw up a comparative table regarding these two environmental problems.

What makes you say that? In the combustion of hydrocarbons, one of the reaction products is carbon dioxide. The greater the number of carbon atoms in the hydrocarbon, the greater the amount of carbon dioxide that is produced.

propane butane

The objective of the combustion of hydrocarbons is to transform chemical energy into another kind of energy. In order to quantify the energy obtained in each reaction, we use the power of combustion parameter (PC), which is expressed in kilojoules (unit of energy) per mole of fuel (kJ/mol). The table shows the PC values of the fuels in the previous activity: Fuel

PC/(kJ/mol)

CH4

890

C2H6

1 560

C3H8

2 220

C4H10

2 900

From these values, calculate, for each one, the amount of carbon dioxide released for each kilojoule of energy. Which fuel is most energyefficient? Which one releases less carbon dioxide into the atmosphere per kilojoule? Based on your results, what conclusions can you draw? Taking into consideration what you have learned, and goal 13.a, what fuel would you choose to produce energy? What other sources of energy are in development to mitigate this fact? Check goal 7.2. 125

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