1.E: Exercises

These are practice exercises to accompany Chapter 1. They are organized by section. For example, the exercises on the material for Section 1, "What is Chemistry" are first. Scroll down to see exercises for other sections. Try your best to work out them out on your own before looking at te answers (listed at the end of each section).

1.1: What Is Chemistry?

Exercises for Section 1.1

1. Which of the following are examples of matter?

A. a baby

B. an idea

C. an emotion

D. the air

E. Alpha Centauri, the closest known star (excluding the sun) to our solar system

F. the light emitted by a star

2. When someone says, “I have a theory that people behave more violently during a full moon,” does that person really have a theory? If it is not a theory, what is it?

Answers (Section 1.1)

1. Which of the following are examples of matter?

A. a baby - MATTER

B. an idea - NOT MATTER

C. an emotion - NOT MATTER

D. the air - MATTER

E. Alpha Centauri, the closest known star (excluding the sun) to our solar system - MATTER

F. the light emitted by a star - NOT MATTER

2. No, that prediction for behavior would be called a hypothesis in science. The next step in the scientific method would be to test the hypothesis. If the hypothesis is supported with extensive data over a long period of time, it might be incorporated into an explanation that could become a theory.

1.2: The Classification of Matter

Exercises for Section 1.2

1. Does each statement refer to a chemical property or a physical property?

A. Balsa is a very light wood. - PHYSICAL

B. If held in a flame, magnesium metal burns in air. - CHEMICAL

C. Mercury has a density of 13.6 g/mL. - PHYSICAL

D. Human blood is red. - PHYSICAL

E. The boiling point of isopropyl alcohol, which is used to sterilize cuts and scrapes, is lower than the boiling point of water. - PHYSICAL

2. Define element. How does it differ from a compound?

3. Identify each substance as an element, a compound, a heterogeneous mixture, or a solution.

A. xenon

B. Sprite

C. solid glucose, C₆H₁₂O₆ 

D. gaseous hydrogen molecules, H₂  

E. dirt, a combination of rocks and decaying plant matter

F. air (on Earth)

4. What word(s) describes each phase change?

A. solid to liquid

B. liquid to gas

C. solid to gas

Answers (Section 1.2)

1. Does each statement refer to a chemical property or a physical property?

A. Balsa is a very light wood.

B. If held in a flame, magnesium metal burns in air.

C. Mercury has a density of 13.6 g/mL.

D. Human blood is red.

E. The boiling point of isopropyl alcohol, which is used to sterilize cuts and scrapes, is lower than the boiling point of water.

2. Define element. How does it differ from a compound? - An element is a substance that cannot be broken down into chemically simpler components. Compounds can be broken down into simpler substances.

3. Identify each substance as an element, a compound, a heterogeneous mixture, or a solution.

A. xenon - element

B. Sprite - homogeneous mixture (if no ice and cap is on bottle so cannot see bubbles); heterogeneous mixture (if can see ice cubes or bubbles separate from the rest of the liquid solution)

C. solid glucose, C₆H₁₂O₆ - compound

D. gaseous hydrogen molecules, H₂  - element

E. dirt, a combination of rocks and decaying plant matter - heterogeneous mixture

F. air (on Earth) - homogeneous mixture (mostly nitrogen and oxygen)

4. What word(s) describes each phase change?

A. solid to liquid - melting or fusion

B. liquid to gas - boiling or evaporation

C. solid to gas - sublimation

1.3: Measurements

Exercises for Section 1.3

1. Why are both parts of a quantity important when describing it?

2. You ask a classmate how much homework your chemistry professor assigned. Your classmate answers, “twenty.” Is that a proper answer? Why or why not?

Answers (Section 1.3)

1. The number states how much, and the unit states of what. Without the number and the unit, a quantity cannot be properly communicated.

2. No, it is not a proper answer; you do not know whether the professor meant homework problem number 20 or 20 homework problems.

1.4: Expressing Numbers: Scientific Notation

Exercises for Section 1.4

1. Why is scientific notation useful in expressing numbers?

2. Express each number in scientific notation.

A.  0.00064

B.  5,230,000

C.  −56,200

D.  0.000000000220

E.  1.0

3.  Express each number in standard form.

A.  6.72 × 10⁴

B.  2.088 × 10⁻⁴

C.  −3 × 10⁶

D.  9.98 × 10⁻⁷

4.  Complete the following table:

Incorrect Scientific Notation	Correct Scientific Notation
54.7 × 10^4
0.0066 × 10^3
3,078 × 10^0

Answers (Section 1.4)

1. Scientific notation is more convenient than listing a large number of zeros.

2.  

A.  6.4 × 10⁻⁴

B.  5.23 × 10⁶

C.  −5.62 × 10⁴

D.  2.20 × 10⁻¹⁰

E.  1.0 × 10⁰

3.

A.  67,200

B.  0.0002088

C.  −3,000,000

D.  0.000000998

4. 

Incorrect Scientific Notation	Correct Scientific Notation
54.7 × 10^4	5.47 × 10^5
0.0066 × 10^3	6.6 × 10^0
3,078 × 10^0	3.078 × 10^3

1.5: Expressing Numbers: Significant Figures

Exercises for Section 1.5

1. Define significant figures. Why are they important?

2. How many significant figures are in each number?

A.  140

B.  0.009830

C.  220,560,000

D.  5.67 × 10³

E.  2.9600 × 10⁻⁵

3.  Round each number to three significant figures.

A.  34,705

B.  34,750

C.  0.001996

4.  Perform each operation and express the answer to the correct number of significant figures.

A.  467.88 + 23.0 + 1,306 = ?

B.  0.00565 + 0.002333 + 0.0991 = ?

C.  439 × 8,767 = ?

D.  23.09 ÷ 13.009 = ?

5.  Use your calculator to solve each equation. Express each answer in proper scientific notation and with the proper number of significant figures. If you do not get the correct answers, you may not be entering scientific notation into your calculator properly, so ask your instructor for assistance.

A.  (5.6 × 10³) × (9.04 × 10⁻⁷) = ?

B.  (8.331 × 10⁻²) × (2.45 × 10⁵) = ?

C.  983.09 ÷ (5.390 × 10⁵) = ?

6. Perform each calculation and express your answer using the correct number of significant digits. (Hint: Think about the appropriate rule as you do each step in the calculation.)

A.  6.78  x 5.903 x (5.489 - 5.01) = ?

B.  (4.562 x 3.99870) / (452.6755 - 452.33) = ?

C.  (1.002 - 0.999) / 3.754 = ?

Answers (Section 1.5)

1. Significant figures represent all the known digits plus the first estimated digit of a measurement; they are the only values worth reporting in a measurement.

2.  

A.  two

B.  four

C.  five

D.  three

E.  five

3.

A.  34,700

B.  34,800

C.  0.00200

4. 

A.  1,797

B.  0.1071

C.  3,850,000

D.  1.775

5.

A.  5.1 × 10⁻³

B.  2.04 × 10⁴

C.  1.824 × 10⁻³

6. 

A.  19

B.  53

C.  0.0008 or 8x10^-4

1.6: The International System of Units

Questions for Section 1.6

1. What property is represented by each of the following measurements? A) 273 K; B) 725 nm; C) 55 cm³; D) 8.1x10⁴ µs

2. Complete the following table:

   Unit	Abbreviation	Exponent & Base Unit
   nanogram
   		10^-3 s
   	Mm
   kiloliter
   	µm
   		10^-2 L

Answers (Section 1.6)

1. What property is represented by each of the following measurements? A) 273 K = temperature; B) 725 nm = length; C) 55 cm³ = volume; D) 8.1x10⁴ µs = time

2. Complete the following table:

   Unit	Abbreviation	Exponent & Base Unit Abbr.
   nanogram	ng	10^-9 g
   milliseconds	ms	10^-3 s
   megameters	Mm	10^6 m
   kiloliter	kL	10^3 L
   micrometers	µm	10^-6 m
   centiliters	cL	10^-2 L

1.7: Converting Units

Exercises for Section 1.7

1. Give the two conversion factors you can construct using each pair of units.

A.  meters and kilometers

B.  liters and nanoliters

C.  seconds and milliseconds

2.  How many meters are in 56.2 km?

3.  How many microliters (µL) are in 44.1 L?

4.  Convert 109.6 kg into micrograms. Express your final answer in scientific notation.

5.  Convert 3.009 × 10⁻⁵ ML into centiliters. Express your final answer in scientific notation.

6.  The density of ethyl alcohol is 0.79 g/mL. What is the mass of 340 mL of ethyl alcohol?

7.  The density of ethyl alcohol is 0.79 g/mL. What is the volume of 340 g of ethyl alcohol?

8.  Convert 55 miles per hour (mph or mi/hr) into meters per second (m/s). (Hints: 1 mi = 1609 m; 1 hr = 60 min; 1 min = 60 s)

9.  Vitamin C tablets can come in 500 mg tablets. How many of these tablets are needed to obtain 10 g of vitamin C?

10. Some brands of aspirin have 81 mg of aspirin in each tablet. If a person takes 8 tablets per day, how many grams of aspirin is that person consuming every day?

Answers (Section 1.7)

1.  

A.   \(\mathrm{\frac{1\:km}{10^3\:m}}\)   or   \(\mathrm{\frac{10^3\:m}{1\:km}}\)   or  \(\mathrm{\frac{1\:km}{1000\:m}}\)   or   \(\mathrm{\frac{1000\:m}{1\:km}}\) 

B.  \(\mathrm{\frac{1\:nL}{10^{-9}\:L}}\)   or   \(\mathrm{\frac{10^{-9}\:L}{1\:nL}}\)   or  \(\mathrm{\frac{1 000 000 000\:nL}{1\:L}}\)   or   \(\mathrm{\frac{1\:L}{1 000 000 000\:nL}}\) 

C.   \(\mathrm{\frac{1\:ms}{10^{-3}\:s}}\)   or   \(\mathrm{\frac{10^{-3}\:s}{1\:ms}}\)   or  \(\mathrm{\frac{1000\:ms}{\:s}}\)   or   \(\mathrm{\frac{\:s}{1000\:ms}}\) 

2.  5.62 × 10⁴ m

3.  4.41 × 10⁷ µL

4.  1.096 × 10¹¹ µg

5.  3.009 × 10³ cL

6.  270 g

7.  430 mL

8.  25 m/s

9. 20 tablets [10 g x \(\mathrm{\frac{1\:mg}{10^{-3}\:g}}\) x \(\mathrm{\frac{1\:tablet}{81\:mg}}\) = 20 tablets]

10. 0.65 g [\(\mathrm{\frac{8\:tablets}{1\:day}}\) x \(\mathrm{\frac{81\:mg}{1\:tablet}}\) x \(\mathrm{\frac{10^{-3}\:g}{1\:mg}}\) = 0.65 g]