1. Give three examples of particulate matter found in air. Explain the difference between PM_2.5 and P1\4₁₀ in terms of size and health effects.

2. Radon is one of the noble gases found in Group 8A on the periodic table. Which properties does it share with the other inert gases? In which way is it distinctly different?

3. a. The concentration of argon in air is approximately 0.9%. Express this value in ppm.

b. The air exhaled from the lungs of a smoker has a concentration of 20-50 ppm CO. In contrast, air exhaled by nonsmokers is 0-2 ppm CO. Express each concentration as a percent.

c.  In a tropical rain forest, the water vapor concentration may reach 50,000 ppm. Express this as a percent.

d. In the dry polar regions, water vapor may be a mere 10 ppm. Express this as a percent.

4. In these diagrams, two different types of atoms are represented by color and size. Characterize each sample as an element, a compound, or a mixture. Explain your reasoning.

5. Express each of these numbers in scientific notation.

a. 1500 m, the distance of a foot race

b. 0.0000000000958 m, the distance between O and H atoms in a water molecule

c. 0.0000075 m, the diameter of a red blood cell

6. Consider this portion of the periodic table and the groups shaded on it.

a. What is the group number for each shaded region?

b. Name the elements that make up each group.

c. Give a general characteristic of the elements in each of these groups.

7. Classify each of these substances as an element, a compound, or a mixture.

a. a sample of "laughing gas" (dinitrogen monoxide, also called nitrous oxide)

b. steam coming from a pan of boiling water

c. a bar of deodorant soap

d. a sample of copper

e. a cup of mayonnaise

f. the helium filling a balloon

8. Balance these equations in which ethane (C₂H₄) burns in oxygen.

a. C₂H₄(g) + O₂(g) → C(s) + H₂O(g)

b. C₂H₄(g) + O₂(g) → CO(g) + H₂O(g)

c. C₂H₄(g) + O₂(g) → CO₂(g) + H₂O(g)

9. Count the atoms on both sides of the arrow to demonstrate that these equations are balanced.

a. 2C₃H₈ (g) + 7O₂ (g) → CO(g) + 8 H₂O (l)

b. 2C₈H₁₈ (g) + 25O₂ (g) → 16 CO₂ (g) + 18 H₂O (/)