Kelter P., Mosher M., Scott A. Chemistry. The Practical Science

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38 Chapter 1 The World of Chemistry

electrodialysis The process of removing unwanted salts

from a solution through a series of semipermeable

membranes by applying an electrical charge. (p. 10)

element A substance that contains only one kind of

atom. All elements are listed in the periodic table of

the elements. (p. 5)

exact number A number that can be known with ab-

solute certainty. Exact numbers possess an inﬁnite

number of signiﬁcant ﬁgures. (p. 28)

extensive property A characteristic of a substance that is

dependent on the quantity of that substance. (p. 23)

heterogeneous mixture A mixture that is not uniformly

mixed, so there are different proportions of the com-

ponents in different parts of the mixture. (p. 8)

homogeneous mixture A mixture that is uniformly mixed

so that it has the same composition throughout. Also

known as a solution. (p. 8)

hypothesis A tentative explanation for an observation—

that is, a statement about what we think might be an

explanation for an observation. (p. 13)

intensive property A characteristic of a substance that is

independent of the quantity of that substance. (p. 23)

International System See SI.

kelvin (K) The SI base unit of temperature. (p. 18)

kilogram (kg) The SI base unit of mass. (p. 17)

kilogram per cubic meter (kg/m

) The derived SI unit

for density. (p. 22)

liter (L) A commonly used unit for volume; equal to

1dm

.(p. 22)

luminous intensity Brightness, expressed in the SI unit

candela (cd). (p. 20)

macroworld A term used to describe the “big world” of

everyday experience, as opposed to the “nanoworld”

of atoms, molecules, and ions, whose activities ulti-

mately determine what happens in the macroworld.

(p. 20)

mass A measure of the amount of matter in a body, de-

termined by measuring its inertia (resistance to

changes in its state of motion) and expressed in

the SI base unit kilogram. (p. 17)

matter Anything that has a mass and occupies space.

(p. 4)

meter (m) The SI base unit of length. (p. 18)

milliliter (mL) One thousandth of a liter. (p. 22)

mixture A sample containing two or more substances.

(p. 8)

mole (mol) The SI base unit of amount of substance.

One mole of entities, such as 1 mole of atoms, is ap-

proximately equal to 6.02214 × 10

entities. (p. 20)

molecule A particle composed of two or more atoms

bonded together. (p. 5)

nanotechnology Technology that depends on manipulat-

ing materials and their chemistry at the very small,

“nanoscale” level of individual particles or assemblies

of small numbers of particles. (p. 36)

nanoworld A term used to describe the “world of the

very small” at the level of individual atoms, mole-

cules, and ions, as opposed to the “macroworld” of

everyday experience. (p. 20)

physical change Change in the physical state of a sub-

stance, such as a change between the solid, liquid, and

gaseous states, that do not involve the formation of

different chemicals. (p. 6)

physical property A characteristic of a substance that can

be determined without changing its chemical compo-

sition. (p. 6)

precision The reproducibility of a measurement. (p. 29)

reverse osmosis The process of purifying water by pass-

ing it through a semipermeable membrane. Dissolved

solutes are unable to pass through the membrane.

(p. 10)

scientiﬁc law Concise description of the behavior of the

natural world. (p. 13)

scientiﬁc method A reliable way to ﬁnd out things about

nature by making use of appropriate combinations of

these key activities: making observations, gathering

data, proposing hypotheses, performing experiments,

interpreting the results of those observations and ex-

periments, checking to ensure that the results are re-

peatable, publishing the results, establishing scientiﬁc

laws, and formulating theories. (p. 12)

second (s) The SI base unit of time. (p. 18)

SI The International System (Système International) of

agreed-upon base units, derived units, and preﬁxes

used to measure physical quantities. (p. 17)

signiﬁcant ﬁgures Those speciﬁc numbers in a measure-

ment whose values we can trust. (p. 31)

solution A homogeneous mixture of solute and solvent.

(p. 8)

state The physical appearance of a chemical, typically

as a solid, liquid, or gas. (p. 10)

substance A type of matter that has a ﬁxed composi-

tion. (p. 6)

theory A trusted explanation of an observation, based

on a hypothesis that has been tested in experiments.

(p. 13)

uncertainty A measure of the lack of conﬁdence in a

measured number. (p. 28)

weight A measure of the gravitational force exerted on

a body. (p. 17)

Focus Your Learning 39

The answers to the odd-numbered problems and some selected

problems appear at the back of the book, as represented by the

blue numbering.

Section 1.1 What Do Chemists Do?

Skill Review

1. Deﬁne the term chemistry. Why is chemistry a science?

2. Explain why chemists need to be inquisitive.

3. In the section, we listed a number of things that chemists do.

Look around the room in which you are sitting. List ﬁve

additional things that you suspect are manufactured using

chemistry.

4. Look on the label of ingredients for ﬁve products in your

kitchen pantry. List some examples of substances that might

be commercially prepared. Why did you choose these? List

some substances that are added in more or less their natural

form. Why did you choose these?

Chemical Applications and Practices

5. The directions for baking a particular cake include the fol-

lowing instruction: “Carefully add 1 cup of water to the

powdered mix and stir.” Use this statement to explain why

measurements are important to the chemist.

6. A scientist has just identiﬁed a new drug for treating cancer.

Use this statement to explain why a scientist communicating

this discovery might need a chemical “shorthand.”

Section 1.2 The Chemist’s Shorthand

Skill Review

7. Deﬁne, differentiate between, and give three examples of an

element and a compound.

8. What dispute might you have with the manufacturer of a

cleanser that was labeled “chemical-free?”

9. How is it possible that oxygen, found in our atmosphere, can

be called an element and a molecule but not a compound?

10. How is it possible that gold, found as ﬂakes in a stream, can

be called an element but not a molecule or a compound?

11. Name one characteristic that a mixture and a compound

have in common.

12. Describe a critical difference between a mixture and a

compound.

13. Which of these chemicals are elements and which are com-

pounds? For the compounds, list the elements that are pre-

sent. You may need to use the periodic table and a chemical

encyclopedia to help you answer some of these.

a. hydrogen gas d. neon

b. sodium chloride (table salt) e. copper sulfate

c. glucose f. titanium

14. Which of these chemicals are elements and which are com-

pounds? For the compounds, list the elements that are

present. You may need to use the periodic table and a chemi-

cal encyclopedia to help you answer some of these.

a. nitrogen gas d. helium gas

b. calcium chloride (sidewalk salt) e. silver metal

c. aspirin f. water

Focus Your Learning

15. Indicate whether each of these is a heterogeneous mixture or

a homogeneous mixture.

a. lake water d. soda

b. yellow notebook paper e. milk

c. marble f. dirt

16. Indicate whether each of these is a heterogeneous mixture or

a homogeneous mixture.

a. tap water d. paint thinner

b. apple juice e. spaghetti sauce

c. beach sand f. air

17. List at least two methods used to separate a homogeneous

mixture.

18. Why are most heterogeneous mixtures easier to separate than

most homogeneous mixtures?

19. For each of these processes, indicate whether a chemical

change or a physical change is taking place.

a. molding melted chocolate into a bar

b. heating your home with a woodstove

c. drying your clothes in the dryer

d. snow melting in the heat of the sun

20. For each of these processes, indicate whether a chemical

change or a physical change is taking place.

a. the yellowing of an old newspaper

b. making hard-boiled eggs

c. magic ink appearing on a piece of paper

d. making dirty clothes clean in the washing machine

Chemical Applications and Practices

21. Some ancient civilizations considered air an “element.” Today

we consider air a mixture, compound (select one). What is the

basis of your choice?

22. Some ancient civilizations considered water an “element.”

Today we consider water a mixture, compound (select one).

What is the basis of your choice?

23. A “health food” store has a poster in its window that says,

“Eat natural food, not chemicals.” Brieﬂy explain what is

wrong with this statement, and try to summarize, in a chem-

ically accurate way, what the writer of the poster was really

trying to say.

24. A box of noodles in a “health food” store indicates that the

noodles are “free of chemicals.” Brieﬂy explain what is wrong

with this statement, and try to summarize, in a chemically

accurate way, what the writer of that phrase was really trying

to say.

Section 1.3 The Scientiﬁc Method

Skill Review

25. Suppose you sit down at your computer to draft an e-mail to

a friend. However, after you have written the e-mail, it ap-

pears that it cannot be sent from your computer. Explain how

you might use parts of the scientiﬁc method to help you solve

this problem.

26. Suppose you wanted to determine which grade, or type, of

gasoline would provide the best miles-per-gallon ratio in

your car. What would be the important variables that you

40 Chapter 1 The World of Chemistry

would control as you used the scientiﬁc method to draw your

conclusion?

27. Which aspects of the scientiﬁc method are most likely to be

subject to interpretation? Which, on the other hand, should

be least ambiguous?

28. For what reasons, apart from the sharing of information, is it

important to publish the results of scientiﬁc studies?

29. How do we distinguish a theory from a hypothesis?

30. We are familiar with how governments enact laws. How is a

scientiﬁc law formed?

Chemical Applications and Practices

31. Several studies have been done to determine the effectiveness

of various vitamins on speciﬁc health issues. Explain how it is

possible for scientiﬁc studies on the same subject to produce

conﬂicting results.

32. As a consumer, you encounter many claims about remedies

for various human conditions from acne to balding. What

aspects of the scientiﬁc method would you expect to see

employed before such claims are made?

33. Assume that ﬁsh are dying in a river that runs through your

town. The river begins in remote mountains, runs through

many miles of farmland, and then passes through a large in-

dustrial area before entering town. What sorts of questions

need to be should be asked in an attempt to learn why the ﬁsh

are dying? What investigations could be carried out to answer

the questions?

34. In an attempt to treat a wart on your hand, you buy a propri-

etary remedy, and two weeks later your wart has disappeared.

Does this prove that the remedy is effective? What steps

should be performed to examine the effectiveness of the rem-

edy in a proper scientiﬁc manner?

Section 1. 4 Units and Measurement

Skill Review

35. Based on the table found in this chapter, arrange these dis-

tances in order from largest to smallest:

1 millimeter 1 terameter 1 kilometer 1 nanometer

36. Based on the table found in this chapter, arrange these masses

in order from largest to smallest:

1 microgram 1 kilogram 1 milligram 1 picogram

37. Complete the conversions:

a. 100 kg to grams d. 3.20 mg to grams

b. 25.9 m to kilometers e. 9.11 nm to picometers

c. 25°C to °F f. 98.6°F to °C

38. Complete the conversions:

a. 150 mL to liters d. 2.33 L to milliliters

b. 8.42 g to milligrams e. 700 mg to grams

c. 48.5°C to °F f. –20°F to °C

39. Complete the conversions:

a. 8.7 kg to milligrams d. 3.20 dL to kiloliters

b. 25.9 dm to meters e. 9.11 s to nanoseconds

c. 190°C to °F f. 350°F to °C

40. Complete the conversions:

a. 3.99 mL to deciliters d. 14.5 L to megaliters

b. 8.42 Mg to kilograms e. 55.5 ks to gigaseconds

c. –40°C to °F f. 75°F to °C

41. A 2.00-L sample of nutrient agar would be able to be divided

into how many equal 100-cm

media containers for a bacter-

ial study?

42. Suppose the nutrient agar described in Problem 41 amounted

to 32 containers, each holding 50 cm

of media. How many

total liters of nutrient agar are in the containers?

43. Using scientiﬁc notation, express 327 kilometers in:

a. meters c. micrometers

b. millimeters d. nanometers

44. Using scientiﬁc notation, express 499 seconds in:

a. milliseconds c. deciseconds

b. microseconds d. kiloseconds

45. A 62.56-g sample of mercury was added to a graduated cylin-

der. It had a volume of 4.60 mL. What is the density of the

mercury?

46. A 22.4-g sample of a substance was added to a graduated

cylinder. It caused a 18.3-mL change in the volume of water

in the cylinder. What is the density of the substance?

47. A 250.0-mL sugar solution had a density of 1.37 g/mL. An

additional 30.0 g of sugar was added to the solution, raising

the volume by 24.6 mL. What is the density of the resulting

sugar solution?

48. A chemist added 17.8 g of salt to 150.0 mL of a salt solution

of unknown density. The resulting solution had a ﬁnal vol-

ume of 165.9 mL and a density of 1.22 g/mL. What was the

density of the original salt solution?

49. List the fundamental units that you would combine to get

these derived units (you may need to look up the meaning of

some of the terms).

a. velocity c. volume

b. acceleration d. speciﬁc heat

50. List the fundamental units that you would combine to get

these derived units (you may need to look up the meaning of

some of the terms).

a. density b. pressure c. energy d. force

Chemical Applications and Practices

51. Which of the following rulers would provide the greatest

number of signiﬁcant ﬁgures in the measurement of the vol-

ume of a cardboard box?

123456789

2468

Focus Your Learning 41

61. Most samples of matter expand when heated. Assuming that

this is the case with water at room temperature, would the

density increase or decrease as the water warmed? Show the

mathematical basis of your answer.

62. Ice ﬂoats on top of water. Using the information from Prob-

lem 61, explain how this could occur and show the mathe-

matical basis of your answer.

63. In casual food preparation, one may be directed to add a

pinch or a smidgeon or “just a bit” of a particular ingredient.

If 10 pinches equaled 2 smidgeons and 10 “just a bits”

equaled 1 smidgeon, how many “just a bits” of hot sauce

should be added to a recipe that calls for 2 pinches?

64. Consider the tongue twister “Peter Piper picked a peck of

pickled peppers.” If two dozen pickled peppers are in a peck,

and Peter Piper picked 8 pecks for his girlfriend Polly, how

many peppers did Peter Piper pick?

Section 1.5 Conversions and Dimensional Analysis

Skill Review

65. Illustrate a plan of attack (in the same manner as indicated

in the text) for converting units of miles per hour (mph) to

meters per second.

66. Illustrate a plan of attack (in the same manner as indicated in

the text) for converting units of kg·m/s

to lb·ft/s

67. Osmium (element 76) is one of the most dense elements

known. The standard density is 22.6 kg/L. What is the density

in units of g/cm

? What would be the mass of a 0.50-L sam-

ple of osmium?

68. Mercury has a density of 13.6 g/cm

. What is the density in

kg/L for mercury? Calculate the weight in pounds of 3.6 L of

mercury.

69. Convert the following into the indicated units:

a. 35 mph to kph c. 733 mi/gal to km/L

b. 22.4 L/s to cm

/s d. 4.184 g/°C to lb/°F

70. Convert the following into the indicated units:

a. 12 doz/lb to gross/kg c. 14.4 lb/in

to kg/m

b. 16 lb/gal to g/mL d. 3.04 °C/min to °F/s

71. In the vacuum of space, light travels at a speed of 186,000

miles per second. Indicare how many miles light travels

through space in:

a. 1 minute b. 1 day c. 1 year

72. The speed of sound varies greatly depending on the medium

and conditions. If the speed of sound at sea level and zero

degrees Celsius is approximately 1100 feet per second, indi-

cate how far sound travels in:

a. 1 millisecond b. 1 dekasecond c. 1 microsecond

73. Perform these conversions:

a. 2.0 oz to pounds d. 96 in to meters

b. 4.0 qt to liters e. 13 ft to centimeters

c. 160 lb to kilograms f. 32 mi to kilometers

74. Perform these conversions:

a. 3.0 kg to pounds d. 134 oz to kilograms

b. 7400 s to days e. 75.5 cm to feet

c. 50.34 mL to gallons f. 2.88 L to quarts

52. Determine the volumes of liquid in each of these graduated

cylinders, and report your answers with the correct number

of signiﬁcant ﬁgures.

53. A fast-food restaurant wants to standardize the temperature

of its coffee. It installs a coffee machine that is speciﬁed as de-

livering coffee at 75°C

± 3°C. What are the maximum and

minimum temperatures of the coffee delivered by this

machine in °F?

54. The temperature of the hot oil bath in a fast-food restaurant

determines the quality of the french fries that are produced.

The heater on the oil bath can regulate the temperature at

350°F ± 10°F. What are the maximum and minimum tem-

peratures of the french fries delivered by this machine in °C?

55. Carbon atoms have an atomic radius of approximately

77 pm. If you drew a line that was 1 cm in length using a piece

of charcoal, approximately how many atoms of carbon

would be in this line? (For the purposes of this question, as-

sume that the atoms are touching and that they form a

straight line one atom wide.)

56. The same piece of charcoal (see Problem 55) was used to

darken a box on a survey form. The box measures 5 mm on

each side. How many atoms of carbon would be in this box?

(For the purposes of this question, assume that the atoms are

touching, that they line up into a square grid, and that they

are only one layer thick on the paper.)

57. During the 1980s, several new elements were synthesized in

Germany. These elements are made of unstable atoms. Half

of the atoms in a sample of unstable atoms will decompose

over a period of time known as the element’s half-life. One of

these newly discovered elements, Meitnerium (element 109)

has a half-life of only 0.07 s.

a. What is its half-life in milliseconds?

b. What is the length of time of four of its half-lives in terms

of microseconds?

58. Before ﬁlling, an empty, irregularly shaped container has a

mass of 0.1956 kg. When this container is totally ﬁlled with

water,the combined mass of the containerand wateris 305.6 g.

Whatis the mass of wateradded to the containerin kilograms?

59. A certain red tomato has a mass of 45.6 g. A green tomato

also has a mass of 45.6 g. However, when placed in water, the

green tomato ﬂoats and the red one sinks. (Try this. Depend-

ing on the degree of ripeness, it actually happens!) Which of

the two is denser? Explain how two tomatoes with the same

mass can have different densities.

60. Various plastics have identiﬁable density values. For example,

you may have heard of high-density polyethylene and low-

density polyethylene. If you had pieces of each that were

equal in volume, which would have the greater mass?

(

)

(b)

42 Chapter 1 The World of Chemistry

75. A typical chemistry lecture lasts for approximately 50 min-

utes. What is that time in years? . . . in centuries? ...in

decades? Report each number using a proper metric preﬁx

that enables you not to have any zeros in your ﬁnal answer.

76. Some people live to be 100 years old. What is that time in sec-

onds? . . . in minutes? . . . in hours? Report each number using

a proper metric preﬁx that enables you not to have any zeros

in your ﬁnal answer.

Chemical Applications and Practices

77. The mass of 6.02 ×10

atoms of gold is approximately 197 g.

a. What is the average mass, in grams, of just one atom of

gold?

b. Select a preﬁx that could more appropriately be used to

report the average mass, and express the mass in that unit.

78. The mass of 6.02 × 10

atoms of carbon is approximately

12 g.

a. What is the average mass, in grams, of just one atom of

carbon?

b. Select another preﬁx that could more appropriately be

used to report the average mass, and express the mass in

that unit.

79. Suppose a football “star” signs a contract for 200 megabucks

over a ﬁve-year period. How many dollars is the star paid per

second? ...per three-hour game?

80. Which is longer; a 100-m soccer ﬁeld or a 100-yd football

ﬁeld? Show the mathematical proof for your answer.

81. Air is a mixture that consists mostly of oxygen and nitrogen.

The density of air varies, depending on temperature and

pressure. However, for this problem let’s assume a reasonable

value for the density of air to be 1.20 mg/cm

. Suppose the

dimensions of your dorm room are approximately 12 ft ×

14 ft × 9.0 ft. What would you calculate to be the approxi-

mate mass of the air in the room?

82. Modern pewter is a mixture of tin, antimony, and copper.

Formerly, pewter also contained lead. If a 1.00-lb sample of a

particular pewter alloy contained, by mass, 95.0% tin and

3.4 % antimony, how many grams of copper must be present

in the sample?

Section 1.6 Uncertainty, Precision, Accuracy,

and Signiﬁcant Figures

Skill Review

83. Some chemists are playing horseshoes. In their version of the

game, each gets four chances to throw a horseshoe to hit a

stake.What can you state about the accuracy and precision of

the chemist that threw the horseshoes to arrive at the out-

come shown here?

84. Two more chemists playing horseshoes each take a turn.

Which of the two outcomes shown here is more precise?

(a)

(b)

85. Three students weighed the same sample of copper shot

three times. Their results were as follows:

a. Calculate the average mass of the sample, as determined by

each student.

b. Which set of measurements is the most precise?

c. If the true mass of the copper shot is 15.384 g, which of the

students was most accurate?

d. What are the main sources of error that could have caused

the differences in the values?

86. The same three students measured the volume of the same

sample of water four times. Their results were as follows:

a. Calculate the average volume of the sample, as determined

by each student.

b. Which set of measurements is the most precise?

c. If the true volume of the water is 24.10 mL, which of the

students was most accurate?

d. What are the main sources of error that could have caused

the differences in the value?

87. Which of these values are quoted using exact numbers? How

many signiﬁcant ﬁgures are there in each of these numbers?

a. 12.000000 g d. 12 L

b. 3125 students e. 1 g

c. 12.2 L f. 42 test tubes

88. Which of these values are quoted using exact numbers? How

many signiﬁcant ﬁgures are there in each of these numbers?

a. 15 apples d. 44 mi

b. 500 people e. 70°C

c. 3.2050 in f. 10 g

Measurement Student 1 Student 2 Student 3

1 25.55 mL 23.79 mL 25.02 mL

2 24.81 mL 24.01 mL 25.10 mL

3 23.03 mL 24.32 mL 25.07 mL

4 24.28 mL 24.19 mL 25.17 mL

Weighing Student 1 Student 2 Student 3

1 17.516 g 15.414 g 13.893 g

2 17.888 g 16.413 g 13.726 g

3 19.107 g 14.408 g 13.994 g

Focus Your Learning 43

89. In each of these numbers, underline any zeros that are con-

sidered signiﬁcant.

a. 0.700 cm d. 100 m

b. 0.101 kg e. 0.01010 g

c. 100.0 cm

90. In each of these numbers, underline any zeros that are con-

sidered signiﬁcant.

a. 1.000 cm d. 0.56 m

b. 80.2 kg e. 3000 g

c. 2104 cm

91. How many signiﬁcant ﬁgures are there in each of these

values?

a. 6.07 × 10

–15

f. 1406.20

b. 0.003840 g. 0.0007

c. 17.00 h. 1600.0

d. 8 × 10

i. 0.0261140

e. 463.8052 j. 1.250 × 10

–3

92. How many signiﬁcant ﬁgures are there in each of these

values?

a. 6.022 ×10

f. 250

b. 1.79 × 10

–19

g. 13.50

c. 3.00 × 10

h. 101.010

d. 14 i. 12.000

e. 0.0035020 j. 550.050

93. Determine the answer for each of these problems. Report

your answer using the rules for signiﬁcant ﬁgures.

a. 3.44 + 6.2 f. 45.6 ÷ 2.4

b. 12.57 − 3.998 g. (754 + 0.8) ÷ 1.3

c. 2.534 + 1.23 + 2.0500 h. (49.53 × 1.20) + 12

d. 12.54 × 5.0 i. (35.865 ÷ 84.2) + 2.3890

e. 84 × 100

94. Determine the answer for each of the problems below.

Report your answer using signiﬁcant ﬁgures rules.

a. 120 + 6.77 f. 140 ÷ 2.9375

b. 453 − 0.32 g. (135 + 3.2) ÷ 1.332

c. 51.8 + 7.225 + 2.01 h. (2.78 × 1.2) + 3.96

d. 2.54 × 32 i. (14.42 − 1.023) ÷ 2.3

e. 36.33 × 0.300

Chemical Applications and Practices

95. Suppose your chemistry textbook fell 10.0 cm from a back-

pack to a desk. Then it slipped off the desk and fell another

0.91 m from the desk to the top of someone’s foot. (Ouch!)

Finally, it fell the remaining 40 mm to the ﬂoor. What is the

total distance, with the correct number of signiﬁcant digits,

that the textbook has fallen?

96. A piece of cheese has a mass of 250.67 g. Four people each

remove a slice of cheese from the piece. The ﬁrst removes

22.5 g of cheese, the second removes 10 g, the third removes

3.557 g, and the fourth takes 80.1 g. How many grams of

cheese remain? Use appropriate signiﬁcant ﬁgure rules to cal-

culate your answer.

97. Molybdenum has a melting point of over 2600

C. It makes

steel stronger, creates colors when added to molten glass,

and is an integral component of some biological molecules

known as enzymes. If you had a sample of the metal that had

a mass of 14.56 g and a volume of 1.43 cm

, what would you

calculate as the density of molybdenum? (Remember to fol-

low the rules for signiﬁcant ﬁgures.)

98. A student obtains the density of water. A 243-mL sample of

water was noted to have a mass of 235.5 g. What does the

student calculate as the density of the water sample? (Re-

member to follow the rules for signiﬁcant ﬁgures.)

Section 1.7 The Chemical Challenges of the Future

Skill Review

99. One of the “future frontiers” mentioned in this chapter

refers to the use of nanotechnology.

a. To what does the preﬁx nano- refer?

b. What would be the diameter, in centimeters, of a wheel

10 nm in diameter?

100. Ozone and other gases in the stratosphere are often mea-

sured in units known as parts per million (ppm). One ppm

ozone is equivalent to 1 g of ozone per million grams of air.

a. Determine the number of grams of ozone in 15 kg of air

containing 2.00 ppm ozone.

b. Which preﬁx would be best suited to identify this

quantity of ozone?

Chemical Applications and Practices

101. Use current Internet resources, or current print media, to

report one advantage and one disadvantage of genetic re-

search on corn. How long have genetically selected plants

been used in agriculture?

102. One method of cancer treatment involves chemotherapy.

What is the chemical connection to this medical term?

103. Depending on their identity and how they are used, chemi-

cals may be harmful or beneﬁcial to our lives. Give two

speciﬁc responses to the question “What has chemistry done

for me?”

104. Ozone, like many other chemicals, may be helpful or harm-

ful. The presence of ozone at high altitudes has advantages

for us. However, at ground level it can cause several prob-

lems. Use other resources to explain how the same molecule

can have such diverse impacts.

105. What are the chief energy problems facing the United

States? How are these similar to or different from those fac-

ing other countries, both economically wealthy and poor?

106. Select one of your answers from Problem 105 and explain

how your knowledge of chemistry might play a role in solv-

ing that problem.

Comprehensive Problems

107. What aspect of daily life do you predict will be most affected

by chemistry in the generation to follow yours?

108. Name ﬁve areas of your life where chemistry plays a major

role.

109. Describe two chemical changes and two physical changes

that are important in growing food crops.

110. Someone remarks that the baking of a cake is a physical

change. Another person says that the process is a chemical

change. Who is right and why?

111. Write a sentence to describe what is happening when you

dissolve some sugar in a cup of warm water.

44 Chapter 1 The World of Chemistry

112. The height of horses is often measured in “hands.” A “hand”

is considered to be 4 inches. Furthermore, up to three-

tenths, each tenth of a hand is considered to be 1 inch. Any

value over three-tenths of a hand is rounded up to the next

hand.

a. What is the height of a horse, in inches, that stands 14.2

hands?

b. How many hands tall is a horse that stands, from the

ground to the top of the withers, 1.6 m tall?

113. Numbers, and their meaning, are very important to the

practicing chemist.

a. How does the meaning of an exact number differ from

that of a number taken from a measurement?

b. Beverages are often sold in six-packs. Six six-packs would

have how many individual containers?

c. Those containers hold a total of 7200 mL of the beverage.

Which of the value(s) represented in this problem are

exact numbers?

114. What are the two most common sources of uncertainty in

measurements? Of the two, which typically produces uncer-

tainty in a consistent direction?

115. Describe two intrinsic and two extrinsic properties of

seawater.

116. A chemist and her family go on vacation and ride the train

to the mountains. They start their journey from Chicago

and travel 1223 miles to Aspen, Colorado. The trip starts at

1:50 p.m. and the train arrives in Aspen at 1:53 p.m. the next

day. How fast, in kilometers per hour, does the train average

during the trip?

117. During a typical cross-country train trip, top speeds of

80.0 miles an hour are reached. What is that speed in

kilometers per second?

118. A student notices that the contents of a 12 fl oz can of diet

soda weigh 340 g.

a. What is the density, in grams per milliliter, of the soda?

b. Will this can of soda ﬂoat on water or sink?

119. A dairy wishes to deliver its milk in large trucks to reduce

the cost of transportation. Assuming that the delivery truck

has a weight of 6500 pounds, how many gallons of milk

(d  1.106 g/mL) could be placed into the truck so that it

could still make it over the small country bridge rated to

hold a maximum of 10.0 tons?

Thinking Beyond the Calculation

120. In a recent study of an allegedly pre-Columbian (before

Columbus) map of the North American continent, one re-

searcher claimed that the map was a forgery because the

black ink had a yellow tinge (older ink would sometimes do

this) that could have been made by ﬁrst laying down the

yellow line and then copying a thinner black line over it.

However, another researcher analyzed the difference

between the boundaries of the black and yellow lines and

claimed, after many measurements, that the differences

were consistently so small that it could not have been done

freehand.

a. Was the second researcher using precision or accuracy to

make his claim? Explain.

b. Describe how the second researcher used the scientiﬁc

method to study the map.

c. If the black lines had an average width of 1.45 mm.

What would that width be in inches? ...in meters? ...in

yards?

121. Biological evolution is a topic that often sparks debate.

Some say it is one of several theories, and others say it is a

fact. The ﬁeld of “chemical evolution,” in which chemists

study how the elements and simple compounds (such as hy-

drogen, methane, and ammonia) combined to form the

molecules of life (including proteins and DNA) has been ac-

tive for nearly a century. Look up the pioneering work of

Miller and Urey using Internet or print resources. Do their

experiments convince you that chemical evolution is possi-

ble? What sorts of experiments would you design to deter-

mine whether chemical evolution occurs? If so, would you

call it a theory or a fact? Why?

122. There has long been a debate about the relationship be-

tween the mathematical preparation of students and their

success in ﬁrst-year chemistry. The debate goes beyond

standardized test scores to social issues. If you were going to

study the relationship between math preparation and suc-

cess in ﬁrst-year chemistry, how would you approach the

problem? Although you would need to consider all aspects

of the scientiﬁc method in your study design, we are espe-

cially interested in three parts. What are the main questions

you would ask? What experiments would you design to an-

swer your questions? And how would you factor other, non-

quantitative data into your results?

Atoms:

A Quest for

Understanding

Fossils can provide evidence that life

existed millions of years ago. New

technologies have been developed

that can “see” evidence that life on

Earth is more than 3.5 billion years

old.

Contents and Selected Applications

Chemical Encounters: How Old Is Life?

2.1 Early Attempts to Explain Matter

2.2 Dalton’s Atomic Theory and Beyond

2.3 The Structure of the Atom

Chemical Encounters: The Dover Boat and Radiocarbon Dating

2.4 Atoms and Isotopes

2.5 Atomic Mass

2.6 The Periodic Table

2.7 Ionic Compounds

2.8 Molecules

2.9 Naming Compounds

2.10 Naming Acids

Go to college.hmco.com/pic/kelterMEE for online learning resources.

How old is life? Scientists have been debating

that issue for quite some time. Xenophanes of

Colophon, an ancient Greek philosopher who died

about 490

B.C., examined fossils of marine life to generate a

hypothesis—a possible explanation based on observations—

about the history of Earth. Since then, scientists have been using

fossils to date life on this planet. Until recently, however, virtually all

fossils of creatures that lived before about 2.5 billion years ago had been

nearly impossible to detect.

In the early 1990s, high-powered microscopes were used

to detect and identify fossils in rocks that were 3.5 billion

years old. Apparently, life had existed on Earth earlier than

anyone had yet imagined. In 1996 a new technique was

developed to examine rocks for the biosignatures of life.

Biosignatures—traces of life left behind when a creature

dies—were identiﬁed using this technique in rocks 3.9 bil-

lion years old. Faint traces of life have also been suggested in

a Martian meteorite found in Antarctica (see Figure 2.1)

and also in rocks found in Greenland and Australia. Is this

evidence clear proof that life on Earth began over 3.5 billion

years ago? Some scientists believe it is, but the debate rages

on. Questions are raised. Experiments are designed and

done. As we discussed in the last chapter, this is the nature

of vibrant science.

What is the new technique that can be used to ﬁnd the

biosignatures of life? All organisms, whether they are mul-

ticellular or single-celled, leave traces where they have

lived. In some cases, these traces can be seen as fossils. In

other cases, particularly the more ancient ones, the biosignature is simply a slight ex-

cess of one kind of a type of matter known as the atom. All organisms are made up of

characteristic concentrations of speciﬁc types of atoms. By measuring larger-than-

normal concentrations of these atoms, scientists can claim to have identiﬁed a biosig-

nature of life. The particular biosignature that led to the discovery of life in the

3.9-billion-year-old rock is a larger-than-normal concentration of carbon-12.

What is carbon-12? It is a speciﬁc set of particles that make up one type of carbon

atom. Although several different sets of particles can give rise to a carbon atom, only

one of these produces the carbon-12 isotope. In this chapter, we’ll learn about the par-

ticles that make up the building blocks of matter called atoms. We’ll uncover the basic

structure of an atom, and we’ll learn how atoms are arranged in the most important

organizational chart used in chemistry: the periodic table of the elements.

2.1 Early Attempts to Explain Matter

As early as 600

B.C., philosophers developed a view that the world was made of a few basic

“elements”—earth, air, water, and ﬁre. The Greek philosopher Democritus (Figure 2.2) wondered

how he could be sitting in one part of his house and detect that bread was baking elsewhere in

the house. Could it be that small particles of the bread were breaking away from the loaf and

Application

HEMICAL ENCOUNTERS:

How Old Is Life?

FIGURE 2.1

An inside look at a meteorite, known simply as ALH84001,

that is presumed to have come from the surface of Mars. In

1996, scientist discovered what appeared to be microfossils

inside this meteorite. The meteorite is estimated to be

about 4.5 billion years old.

traveling through the air and into his nose? Noticing that wet clothing gradually

got drier and lighter led to the explanation that small, invisible pieces of water

were gradually leaving the clothing. What was the smallest possible piece of this

matter? In Democritus’ culture, these pieces of matter were thought to be indi-

visible, unable to be broken down further, or uncuttable. In their language, the

particles of the basic elements were atomos. This is the origin of the modern word

atom.

The lack of certain instruments that we use routinely today made it impossi-

ble, in Democritus’ time, to perform the experiments that have led to our current

understanding of matter. For instance, the invention of the balance for measur-

ing mass was one of the most signiﬁcant experimental advances in the history of

science. In fact, two important chemical laws were discovered with the use of the

balance. These laws helped to shape our current understanding of the ideas put

forth in Democritus’ era.

The Law of Conservation of Mass

The French scientist Antoine Lavoisier (1743–1794) used the most precise

balances of his time, shown in Figure 2.3, to examine a variety of chemical

processes (chemical reactions). From his repeated measurements, Lavoisier con-

cluded that the total mass of the

reactants (what is consumed in a reaction) did

not differ from the total mass of the

products (what is produced in the reaction).

In other words, matter is neither created nor destroyed in a chemical reaction.We

call this conclusion the

law of conservation of mass.

Strictly speaking, this law is not precisely true because of the tiny

changes in mass resulting from something we’ll discuss in Section 21.5: the

mass-energy equivalence discovered by Albert Einstein. However, the law of

conservation of mass is accurate enough to indicate a fundamental truth

about chemical reactions: The atoms with which you start are the same as the

ones with which you end. When atoms participate in chemical reactions,

they are not destroyed or replaced by newly made atoms but, rather, are

rearranged. DNA, the genetic code in our cells, is composed of atoms of

carbon, hydrogen, oxygen, nitrogen, and phosphorus. Arranged in one way,

these atoms are the genes that lie at the heart of the chemistry of life.

Arranged in other ways, they are a mixture of water, carbon dioxide gas,

and a fertilizer called ammonium phosphate. Arranged in still other ways,

they form parts of biosignatures from billions of years ago.

The Law of Deﬁnite Composition

Another French scientist, Joseph Louis Proust (1754–1826; see Figure 2.4),

studied the composition of various minerals. In 1799 he published his work

about a compound that contained copper, carbon, oxygen, and hydrogen.

His results indicated that every time he determined the composition of his

mineral, the components of the compound were always present in the same

2.1 Early Attempts to Explain Matter 47

FIGURE 2.2

The Greek philosopher Democritus

(460

B.C.–370 B.C.). His early deductions

about the composition of the basic

components of nature led him to believe

in unseen and uncuttable particles, called

atomos.

FIGURE 2.3

Using balances such as these, Lavoisier and

others were able to reach conclusions about the

nature of chemical reactions.

FIGURE 2.4

Joseph Proust (1754–1826) was born in Angers,

France. He was a professor at different institutions in

Spain. In 1797 he published his understanding of the

Law of Deﬁnite Proportions. After returning to France

in 1808, he spent considerable time investigating

foodstuffs and discovered the molecule leucine, one

of the building blocks of proteins.