# CHEMISTRY: The Molecular Nature of Matter and Change 2016

## Educators

CW
BI
SA

### Problem 1

Scenes A–D represent atomic-scale views of different samples of substances:
(a) Under one set of conditions, the substances in A and B mix, and the result is depicted in C. Does this represent a chemical or a physical change?
(b) Under a second set of conditions, the same substances mix, and the result is depicted in D. Does this represent a chemical or a physical change?
(c) Under a third set of conditions, the sample depicted in C changes to that in D. Does this represent a chemical or a physical change?
(d) After the change in part (c) has occurred, does the sample have different chemical properties? Physical properties?

Dalton H.

### Problem 2

Describe solids, liquids, and gases in terms of how they fill a container. Use your descriptions to identify the physical state (at room temperature) of the following: (a) helium in a toy balloon; (b) mercury in a thermometer; (c) soup in a bowl.

CW
Charles W.

Dalton H.

CW
Charles W.

### Problem 5

Define physical change and chemical change. State which type of change occurs in each of the following statements:
(a) Passing an electric current through molten magnesium chloride yields molten magnesium and gaseous chlorine.
(b) The iron in discarded automobiles slowly forms reddish brown, crumbly rust.

Dalton H.

### Problem 6

Which of the following is a chemical change? Explain your reasoning: (a) boiling canned soup; (b) toasting a slice of bread; (c) chopping a log; (d) burning a log.

BI
Brian I.

### Problem 7

Which of the following changes can be reversed by changing the temperature: (a) dew condensing on a leaf; (b) an egg turning hard when it is boiled; (c) ice cream melting; (d) a spoonful of batter cooking on a hot griddle?

Dalton H.

### Problem 8

For each pair, which has higher potential energy?
(a) The fuel in your car or the gaseous products in its exhaust
(b) Wood in a fire or the ashes after the wood burns

SA
Susan A.

### Problem 9

For each pair, which has higher kinetic energy?
(a) A sled resting at the top of a hill or a sled sliding down the hill
(b) Water above a dam or water falling over the dam

Dalton H.

### Problem 10

The alchemical, medical, and technological traditions were precursors to chemistry. State a contribution that each made to the development of the science of chemistry.

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### Problem 11

How did the phlogiston theory explain combustion?

Dalton H.

### Problem 12

One important observation that supporters of the phlogiston theory had trouble explaining was that the calx of a metal weighs more than the metal itself. Why was that observation important? How did the phlogistonists respond?

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### Problem 13

Lavoisier developed a new theory of combustion that overturned the phlogiston theory. What measurements were central to his theory, and what key discovery did he make?

Dalton H.

### Problem 14

How are the key elements of scientific thinking used in the following scenario? While making toast, you notice it fails to pop out of the toaster. Thinking the spring mechanism is stuck, you notice that the bread is unchanged. Assuming you forgot to plug in the toaster, you check and find it is plugged in. When you take the toaster into the dining room and plug it into a different outlet, you find the toaster works. Returning to the kitchen, you turn on the switch for the overhead light and nothing happens.

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### Problem 15

Why is a quantitative observation more useful than a nonquantitative one? Which of the following is (are) quantitative? (a) The Sun rises in the east. (b) A person weighs one-sixth as much on the Moon as on Earth. (c) Ice floats on water. (d) A hand pump cannot draw water from a well more than 34 ft deep.

Dalton H.

### Problem 16

Describe the essential features of a well-designed experiment.

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### Problem 17

Describe the essential features of a scientific model.

Dalton H.

### Problem 18

Explain the difference between mass and weight. Why is your weight on the Moon one-sixth that on Earth?

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### Problem 19

When you convert feet to inches, how do you decide which part of the conversion factor should be in the numerator and which in the denominator?

Dalton H.

### Problem 20

For each of the following cases, state whether the density of the object increases, decreases, or remains the same:
(a) A sample of chlorine gas is compressed.
(b) A lead weight is carried up a high mountain.
(c) A sample of water is frozen.
(d) An iron bar is cooled.
(e) A diamond is submerged in water.

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### Problem 21

Explain the difference between heat and temperature. Does 1 $\mathrm{L}$ of water at $65^{\circ} \mathrm{F}$ have more, less, or the same quantity of energy as 1 $\mathrm{L}$ of water at $65^{\circ} \mathrm{C} ?$

Dalton H.

### Problem 22

A one-step conversion is sufficient to convert a temperature in the Celsius scale to the Kelvin scale, but not to the Fahrenheit scale. Explain.

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### Problem 23

Describe the difference between intensive and extensive properties. Which of the following properties are intensive: (a) mass; (b) density; (c) volume; (d) melting point?

Dalton H.

### Problem 24

Write the conversion factor(s) for
(a) $\mathrm{in}^{2}\mathrm{tom}^{2} \quad$ (b) $\mathrm{km}^{2}$ to $\mathrm{cm}^{2}$
(c) $\mathrm{mi/h}$ to $\mathrm{m} / \mathrm{s} \quad$ (d) $\mathrm{Ib} / \mathrm{ft}^{3}$ to $\mathrm{g} / \mathrm{cm}^{3}$

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### Problem 25

Write the conversion factor(s) for
(a) $\mathrm{cm} / \mathrm{min}$ to $\mathrm{in} / \mathrm{s} \quad$ (b) $\mathrm{m}^{3}$ to $\mathrm{in}^{3}$
(c) $\mathrm{m} / \mathrm{s}^{2}$ to $\mathrm{km} / \mathrm{h}^{2} \quad$ (d) $\mathrm{gal} / \mathrm{h}$ to $\mathrm{L} / \mathrm{min}$

Dalton H.

### Problem 26

The average radius of a molecule of lysozyme, an enzyme in tears, is 1430 pm. What is its radius in nanometers (nm)?

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### Problem 27

1.27 The radius of a barium atom is $2.22 \times 10^{-10} \mathrm{m} .$ What is its radius in angstroms ( A)?

Dalton H.

### Problem 28

What is the length in inches (in) of a 100.-m soccer field?

SA
Susan A.

### Problem 29

The center on your school’s basketball team is 6 ft 10 in tall. How tall is the player in millimeters (mm)?

Dalton H.

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### Problem 81

Brass is an alloy of copper and zinc. Varying the mass percentages of the two metals produces brasses with different properties. A brass called yellow zinc has high ductility and strength and is $34-37 \%$ zinc by mass. (a) Find the mass range (in g) of copper in 185 g of yellow zinc. (b) What is the mass range (in g) of zinc in a sample of yellow zinc that contains 46.5 $\mathrm{g}$ of copper?

Dalton H.

### Problem 82

Liquid nitrogen is obtained from liquefied air and is used industrially to prepare frozen foods. It boils at 77.36 $\mathrm{K}$ . (a) What is this temperature in $^{\circ} \mathrm{C} ?$ (b) What is this temperature in $^{\circ} \mathrm{F} ?$ (c) At the boiling point, the density of the liquid is 809 $\mathrm{g} / \mathrm{L}$ and that of the gas is 4.566 $\mathrm{g} / \mathrm{L}$ . How many liters of liquid nitrogen are produced when 895.0 $\mathrm{L}$ of nitrogen gas is liquefied at 77.36 $\mathrm{K}$ ?

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### Problem 83

A jogger runs at an average speed of 5.9 mi/h. (a) How fast is she running in $\mathrm{m} / \mathrm{s} ?$ (b) How many kilometers does she run in 98 $\min ?(\mathrm{c})$ If she starts a run at $11 : 15 \mathrm{am},$ what time is it after she covers $4.75 \times 10^{4} \mathrm{ft}$ ?

Dalton H.

### Problem 84

Scenes A and B depict changes in matter at the atomic scale:
(a) Which show(s) a physical change?
(b) Which show(s) a chemical change?
(c) Which result(s) in different physical properties?
(d) Which result(s) in different chemical properties?
(e) Which result(s) in a change in state?

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### Problem 85

If a temperature scale were based on the freezing point $\left(5.5^{\circ} \mathrm{C}\right)$ and boiling point $\left(80.1^{\circ} \mathrm{C}\right)$ of benzene and the temperature difference between these points was divided into 50 units (called $^{\circ} \mathrm{X} ),$ what would be the freezing and boiling points of water in $^{\circ} \mathrm{X} ?$ (See Figure $1.11, \mathrm{p} .25 . )$

Dalton H.
Earth's surface area is $5.10 \times 10^{8} \mathrm{km}^{2} ; \mathrm{its}$ crust has a mean thickness of 35 $\mathrm{km}$ and a mean density of 2.8$/ \mathrm{cm}^{3} .$ The two most abundant elements in the crust are oxygen $\left(4.55 \times 10^{5} \mathrm{g} / \mathrm{t}, \text { where t }\right.$ stands for "metric ton"; $1 \mathrm{t}=1000 \mathrm{kg}$ ) and silicon $\left(2.72 \times 10^{5} \mathrm{g} / \mathrm{t}\right)$, and the two rarest nonradioactive elements are ruthenium and rhodium, each with an abundance of $1 \times 10^{-4} \mathrm{g} / \mathrm{t}$ . What is the total mass of each of these elements in Earth's crust?