Student Activities - Chapter 1

• 1. Students should read the Ecology Focus, The Harm Done by Acid Deposition, before coming to class. They should also collect and bring in water samples from their dorm faucets, drinking fountains, rainwater, or a nearby pond or stream. Have pH paper available in class to determine the pH of these samples. Discuss the known or potential effects of acid rain in your particular geographic location, which might include: effects on forests, including interruption of the symbiotic association between trees and their mycorrhizae, depletion of fisheries in lakes, or deterioration of car finishes and statues.

• 2. Demonstrate how pH changes as substances interact with classroom air. At the beginning of the class period, open one or more bottles or cans of soft drinks, and pour small samples into several paper cups. Have student volunteers use pH indicator papers to measure the pH of the soda pop. Record the results on the chalkboard. At the end of the class period, have students remeasure the pH of the soda pop. It should become less acidic as carbon dioxide leaves the soda pop and equilibrates with the classroom air. (Use of a gooseneck lamp over the cups speeds this process. Alternatively, pour cups of soda pop the night before, being careful not to expose them to contaminants if you wish students to taste them. A can of soda pop itself left open overnight on a shelf will generally lose most of its fizz.) Students can also taste-test the soft drinks before and after the class period to see if they detect differences in taste. The soda pop will taste flat after it loses its fizz. Hint: Pouring only a small amount of soda pop in each paper cup allows the pop to lose its carbon dioxide more rapidly. It will take longer if you fill the cup to the rim. Also, using several different brands or flavors of soda pop and comparing results makes this exercise more entertaining.

Nutrition Labels

• 3. Ask students to bring to class the label from their favorite breakfast cereal box, bread wrapper, potato chip sack, or other snack food package. Compile a list of the foods represented on the chalkboard, and pick out several categories of organic molecules (nutrients) for comparison. For each food, write the number of fat grams, protein grams, and carbohydrate grams. This discussion helps students make the connection between types of organic molecules and their functions in the diet and in cells.