Waters states of matter include steam liquid water and ice. What about water is the same in the states? What can you conclude about what changes and what does not change during a change of state?

This lesson is the first in a three-part series that addresses a concept that is central to the understanding of the water cycle-that water is able to take many forms but is still water. This series of lessons is designed to prepare students to understand that most substances may exist as solids, liquids, or gases depending on the temperature, pressure, and nature of that substance. This knowledge is critical to understanding that water in our world is constantly cycling as a solid, liquid, or gas.

In these lessons, students will observe, measure, and describe water as it changes state. It is important to note that students at this level " ... should become familiar with the freezing of water and melting of ice (with no change in weight), the disappearance of wetness into the air, and the appearance of water on cold surfaces. Evaporation and condensation will mean nothing different from disappearance and appearance, perhaps for several years, until students begin to understand that the evaporated water is still present in the form of invisibly small molecules." (Benchmarks for Science Literacy, pp. 66-67.)

In this lesson, students explore how water can change from a solid to a liquid and then back again.

In Water 2: Disappearing Water, students will focus on the concept that water can go back and forth from one form to another and the amount of water will remain the same.

Water 3: Melting and Freezing allows students to investigate what happens to the amount of different substances as they change from a solid to a liquid or a liquid to a solid.