No lab required.

After reading "Vanishing Forest" (p. 18), try this activity.

PREDICT

In which container would you expect water to evaporate, or change from a liquid to a gas, more quickly: one with a larger or smaller surface area (area that is exposed)?

MATERIALS

1 measuring cup * 1 disposable loaf pan (10.5 cm by 23 cm, or 4 in. by 9 in.) * 1 mug (0.5 L, or 2 cups) * water (550 ml, or 2.2 cups) * 2 paper towels * 2 plastic plates * graph paper * pencil

PROCEDURE (PART 1)

1 Pour 250 ml (1 cup) of water into a loaf pan. Pour the same amount of water into a mug.

2 Place both containers in a sunny place. Note the time of the day.

3 You will keep track of the amount of water in both containers for five days. Create a data table to help you organize your findings. For Day 1, record "250 ml" as the water amount for the pan, and also for the mug.

4 The next day at the same time, pour the remaining water from the pan into a measuring cup. Record the water amount.

5 Pour the water back into the pan, and place the pan in a sunny spot.

6 Repeat Steps 4 and 5 with the mug.

7 Repeat Steps 4 through 6 every day for three more days.

8 After Day 5, create a double-line graph with the data. (Hint: The "day" will go on the x-axis, and the water amount will go on the y-axis.)

CONCLUSIONS (PART 1)

1 Study your graph. From which container did water evaporate faster: the pan or the mug?

2 How did each container's surface area affect the rate of evaporation?

1. The water in the loaf pan should have evaporated more quickly

2. Surface area affected the results The loaf pan has a larger surface area than the mug. With a larger surface area, the loaf pan exposed more of the water's surface to the air, allowing it to evaporate faster. The mug has a smaller surface area So less of the water's surface was exposed to air, hindering its evaporation.

PROCEDURE (PART 2)

1 Use what you learned in Part 1 to predict which of the following would retain more water: a flat, broad leaf or a needle-shaped leaf.

2 Place a paper towel flat onto a plastic plate. This represents a tree's "flat, broad leaf."

3 Tightly roll up one paper towel lengthwise, and place it onto another plastic plate. This is a "needle-shaped leaf."

4 Pour 25 ml (0.1 cup) of water evenly over each paper towel.

5 Observe both paper towels: How wet does each paper towel look and feel? Record your observations.

6 Place both plates in a sunny spot.

7 After three hours, observe the paper towels again. Record your observations.

CONCLUSIONS (PART 2)

1 Which paper towel had retained more water after three hours?

2 How could needle-shaped leaves help a coniferous tree retain water?

1. The rolled-up paper towel should have retained more water than the flat paper towel That's because a flat paper towel has a larger surface area than a rolled-up one, allowing the water to evaporate more quickly from the flat towel.

2. Because needle-shaped leaves have a smaller surface area than flat, broad leaves, water would evaporate more slowly from a needle leaf. A slower rate of evaporation would allow a conifer tree to conserve more water than if the tree had flat, broad leaves