Critical Thinking Activities - Chapter 2

Question 1. The water that is drawn through trees by transpiration, and evaporates into the air above forests, generates updrafts of lighter weight moist air! Glider pilots know that they can gain lift from these currents above forests. Consider that a molecule of water displaces a molecule of nitrogen or oxygen gas. Why then is air lighter when we add moisture to it?

Question 2. The discovery of liquid water under the frozen surface of a distant moon in our solar system has caused scientists to speculate on the possibility of life on that moon. Researchers hold no hope of any life form existing on any planet or moon in the absence of water. Why?

Answers are available to instructors in the Instructor's Manual.
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