Activity 2: Hydrologic Cycle
WATER: AMAZING AND PHASING
Water comes in three different phases which play a very important part in the hydrologic cycle. Activities demonstrate changes that take place as water passes through each of the phases.
Instructional Method: Experiment
Goal: To show students how water passes through phases.
Objectives: Students will be able to:
Set up: 20 min.
The three phases of water include: liquid, solid ice, and gaseous vapor. One drop of water can change into each of these phases perpetually, without losing or gaining any mass.
Freezing is the act of water changing from a liquid to a solid (ice). Melting is the act of ice changing into liquid water. Boiling is the act of water changing from liquid into vapor. Condensation is the act of water vapor changing into a liquid.
Phase changes often are associated with either a boiling point or a freezing point. Boiling point is the temperature at which a liquid actively changes into a vapor. The boiling point of water is 212°F (100°C). Freezing point is the temperature at which a liquid is actively changed into a solid. The freezing point of water is 32°F (0°C). If water vapor is cooled below the boiling point, it condenses and goes back to its liquid form. If ice is warmed above the freezing point, it melts and changes into its liquid form. If you continue to warm liquid from melting ice it eventually reaches its boiling point and changes into vapor.
Older students may also want to explore the idea of sublimation, the act of a solid changing directly into vapor without going through the liquid phase. On sunny winter days, sublimation is visible as snow disappears without making the sidewalk wet.
In this activity we will explore the three basic phases of water and try to predict the boiling and freezing points based on observations and temperature readings.
Part I: Liquid and Vapor
Where did the water in the cold flask come from? How did it get there? Which two phases of water did we see? What does it mean to boil? What does it mean to condense? What is the third phase of water?
Part II: Liquid and Solid
What happened to the water? What does it mean to freeze? Why was the water deeper when it was frozen than when it was liquid? When do we see solid water in nature? What happens to solid water in nature? Do oceans boil? Can water be changed into a vapor without boiling first? Where do we see phase changes in the hydrologic cycle? How do we know when water changes phases in the hydrologic cycle?
Included National Parks and other sites:
Utah Science Core:
1st Grade Standard 2 Objective 1