Type:
Solution Manual
Resource:
Chemistry
Edition:
7th Edition
Author(s):
John E. McMurry Robert C. Fay Jill Robinson
CHAPTER 1 CHEMICAL TOOLS: EXPERIMENTATION AND MEASUREMENT Chapter Learning Goals for Students Section 1.1
Identify the steps involved in the scientific method. Differential between a qualitative and a quantitative measurement.
Section 1.2
Write numbers in scientific notation and use prefixes for multiples of SI units.
Section 1.3
Describe the difference between mass and weight. Convert between different prefixes used in mass measurements.
Section 1.4
Convert between different prefixes used in length measurements.
Section 1.5
Convert between common units of temperature measurement.
Section 1.6
Convert between SI and metric units of volume. Convert between different prefixes used in volume measurements.
Section 1.7
Calculate mass, volume, or density using the formula for density. Predict whether a substance will float or sink in another substance based on density.
Section 1.8
Calculate the kinetic energy of a moving object. Convert between common energy units.
Section 1.9
Specify the number of significant figures in a measurement. Evaluate the level of accuracy and precision in a data set. Report a measurement to the appropriate number of significant figures.
Section 1.10
Report the answer of a mathematical calculation to the correct number of significant figures. Round a measurement to a specified number of significant figures.
Section 1.11
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Change a measurement into different units using appropriate conversion factors.
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Chapter 1—Chemical Tools: Experimentation and Measurement
Lecture Outline Introduction 1.1. The Scientific Method in a Chemical Context: Improved Pharmaceutical Insulin A. Scientific method – systematic approach to research 1. Observations – qualitative descriptions or quantitative measurements 2. Hypothesis – possible explanation of the observations 3. Experimentation – testing of the hypothesis 4. Theory – consistent explanation of known observations and logical interpretations of experimental results; has predictive power and can be modified or replaced B. Scientific method applied to Humalog® 1. Observation – aggregation of injected insulin lessens its ability to act like insulin produced by the human body 2. Hypothesis – the chemical structure of insulin led to this problem and that modifying its chemical structure could change its behavior in the body 3. Experimentation – insulin analogs produced and tested; Humalog® developed which mimics the behavior of insulin produced by the human body 4. Theory – modeling showed that the last five amino acids in the B-chain were important in aggregation but not biological activity 1.2. Experimentation and Measurement1 A. International System (SI) of Units – seven base units (and units derived from them) that suffice for all scientific measurements (textbook Table 1.3) B. Common prefixes used to modify SI units 1. giga (G); factor = 109 2. mega (M); factor = 106 3. kilo (k); factor = 103 4. deci (d); factor = 10–1 5. centi (c); factor = 10–2 6. milli (m); factor = 10–3 7. micro (); factor = 10–6 8. nano (n); factor = 10–9 C. Scientific notation – exponential format for very large or very small numbers (textbook Appendix A) D. All measurements of physical quantities contain a 1. number 2. unit label 1.3. Mass and Its Measurement2 A. Mass (SI unit = kg) – amount of matter in an object B. Matter – anything physically real C. Weight – pull of gravity on an object D. Mass of an object 1. Measured on a balance 2. A comparison of the weight of the object to the weight of a reference standard of known mass 1.4 Length and Its Measurement3 A. Meter 1. Standard SI unit of length 2. Distance traveled by light in a vacuum in 1/299,792,458th of a second 1.5. Temperature and Its Measurement4 Test Item Questions: Multiple Choice 4 – 10, Algorithmic 1 – 13, Short Answer 3 – 4 Test Item File Questions: Multiple Choice 11 – 15, Algorithmic 14 – 20, Short Answer 5 3 Test Item File Questions: Multiple Choice 16 – 19, Algorithmic 21 – 26, Short Answer 6 4 Test Item File Questions: Multiple Choice 20 – 26, Algorithmic 27 – 29, Short Answer 7 1 2
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Chapter 1—Chemical Tools: Experimenation and Measurement A. Common unit – Celsius degree (oC) B. Scientific unit – Kelvin C. Celsius and Kelvin scales –100 degrees between the freezing point and boiling point of water Temperature in K = temperature in C + 273.15 Temperature in C = temperature in K – 273.15 D. Fahrenheit scale –180 between the freezing point and boiling point of water 1. 180F encompasses the same range as 100C 180 oC 9 1 oC ´ = ´ oF 5 100 o F E. Conversion from Celsius to Fahrenheit 1. Size correction 2. Followed by zero-point correction F. Conversion from Fahrenheit to Celsius 1. Zero-point correction 2. Followed by a size correction æ 9 oF ö o F = ç o ´ oC÷ + 32 o F è5 C ø o
C =
5 oC 9 oF
( F - 32 F ) o
o
1.6. Derived Units: Volume and Its Measurement5 A. Derived quantities – quantities expressed in terms of one or more of the seven base units (See textbook Table 1.5.) B. Volume – amount of space occupied by an object 1. Measured in SI units by the cubic meter (m 3) 2. Commonly used measurements: a. Cubic decimeter (dm3) = metric liter (L) b. Cubic centimeter (cm3) = metric milliliter (mL) 1.7. Derived Units: Density and Its Measurement6 A. Density – intensive property relating mass to volume 1. Expressed in units of g/cm3 or g/mL 2. Temperature dependent property 3. Useful property – allows conversion of a liquid’s volume to mass 1.8. Derived Units: Energy and Its Measurement7 A. Energy 1. Capacity to do work or supply heat 2. Energy = work + heat B. Kinetic energy 1. Energy of motion 2. EK = 1/2mv2 C. Potential energy – stored energy D. Joule 1. SI unit for energy 2. 1 J = 1(kgm2)/s2 E. Calorie 1. Amount of energy necessary to raise the temperature of 1 g of water by 1C 2. 1 cal = 4.184 J Test Item File Questions: Multiple Choice 27, Algorithmic 30 – 36, Short Answer 8 – 9 Test Item File Questions: Multiple Choice 28 – 37, Algorithmic 38 – 41, Short Answer 10 – 11 7 Test Item File Questions: Multiple Choice 38 – 40, Algorithmic 42 – 44, Short Answer 12 – 13 5 6
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Chapter 1—Chemical Tools: Experimentation and Measurement 3. Nutritional calorie (Calorie) 4. 1 Cal = 1000 cal = 1 kcal = 4.184 kJ 1.9. Accuracy, Precision, and Significant Figures in Measurement8 A. Accuracy – how close a measurement is to the true value B. Precision – how well a number of independent measurements agree with one another 1. To indicate the precision of a measurement use all the digits known with certainty, plus one additional estimated digit 2. Number of digits in the measurement = number of significant figures C. Determining the number of significant figures – see rules in textbook D. Using scientific notation – helpful in determining number of significant figures E. Exact numbers – infinite number of significant figures 1.10. Rounding Numbers9 A. In carrying out a multiplication or division, the answer can’t have more significant figures than either of the original numbers. B. In carrying out an addition or subtraction, the answer can’t have more digits to the right of the decimal point than either of the original numbers. C. Rules for rounding off numbers 1. See text 2. Doing calculations a. Use all figures, significant or not b. Only round off final answer 1.11. Calculations: Converting from One Unit to Another 10 A. Dimensional analysis method 1. Quantity described in one unit converted into an equivalent quantity described in a different unit 2. Conversion factor used to express relationship between units Starting quantity conversion factor = equivalent quantity 3. Units a. Treated like numbers b. Can be multiplied and divided 4. Equation a. Set up so that all unwanted units cancel b. Leave only desired units c. Correct answer obtained only if equation set up so unwanted units cancel 5. Method: a. Start with given information, including units b. Identify information needed, including units c. Find relationship between known information and unknown answer d. Plan a strategy to get from known information to unknown answer e. Solve i. Use conversion factor that allows units in given information to cancel ii. Continue conversion factor use to cancel the previous unit until desired unit remains f. Consider whether answer obtained is reasonable (Refer to Ballpark Check in textbook.) 6. Number of significant figures in answer determined from given information Inquiry – What Are the Unique Properties of Nanoscale Materials? 11
Test Item File Questions: Algorithmic 45 – 53, Short Answer 14 – 15 Test Item File Questions: Multiple Choice 41 – 44, Algorithmic 54 – 61, Short Answer 16 10 Test Item File Questions: Multiple Choice 45 – 49, Algorithmic 62 – 66, Short Answer 17 11 Test Item File Questions: Algorithmic 67 – 68 8 9
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Chapter 1—Chemical Tools: Experimenation and Measurement
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Chapter 1—Chemical Tools: Experimentation and Measurement
CHAPTER 1 CHEMICAL TOOLS: EXPERIMENTATION AND MEASUREMENT Teaching Tips, Points of Emphasis, and Common Misconceptions Section 1.1
Chemistry is an experimental science. Challenge students to sharpen their skills of observation and measurement, relating laboratory work to concepts discussed in lecture.
Section 1.1
A theory provides the best explanation based on available information. Additional data can result in modification or replacement of the theory.
Section 1.2
All systems of measurement are based on arbitrary standards. The SI system is as arbitrary as the English system, but the relationship of one unit to another is more systematic and easier to remember in the metric system.
Section 1.2
For very large or very small quantities, commonly used prefixes represent amounts that vary by three powers of 10, for example, milli, micro, nano, and pico (10–3, 10–6, 10–9, and 10–12, respectively).
Section 1.6
Remind students to raise both the measured number and unit to the appropriate power when dealing with areas and volumes. For example, (3 cm)3 = 33 cm3 = 27 cm3, not 3 cm3 or 27 cm.
Section 1.7
Density is sometimes confused with mass. A kg of feathers weighs the same as a kg of gold, but gold occupies less space because it has a greater density, the ratio of mass to volume.
Section 1.7
Because students are very familiar with water they tend to use it as a standard when relating the density of a solid to the density of a liquid. Most solids sink in their liquids; water is unusual in that ice floats atop liquid water.
Section 1.9
Significant figures tend to be abstract to students until they realize that significant figures are a shortcut to expressing the limitations of laboratory measurements.
Section 1.9
Only measured quantities may contain a measured error, which limits the number of significant figures. In addition to counted objects (7 days = 1 week), numbers related by definition (1 in = 2.54 cm) are exact numbers with an infinite number of significant figures.
Section 1.10
The answer given to a series of calculations involving measured quantities is limited by the least precise measurement.
Section 1.10
Students can avoid round-off errors by always using one more significant figure for constants or molar masses than required by measured data and rounding off only the final answer and not intermediate ones.
Section 1.10
Based on calculator displays, students often report answers to problems that contain too many or too few significant figures. Remind students that calculators are incapable of distinguishing between measured and exact quantities. One consequence is that calculators do not record a zero at the end of numbers even when the zero may be a significant figure.
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