In these lessons, students will observe, measure, and describe water as it changes state.
Ask students the following questions:
* Has anyone ever eaten ice cream on a hot summer day? What happens to it if it is not eaten?
* Have you ever left a glass of ice water out on the table? What happened to the ice?
* Have you ever noticed what happens to frozen objects as they heat up?
* What happens to the amount of a substance if it is changed from a solid to a liquid?
Next, show students a baggie filled with ice. Ask students to predict what will happen to the substance
Have students put the ice into the baggie and seal it. Have them record their observations of the ice at this time, and then record the weight of the bag of ice. Have students take turns holding the bag in their hands, wiping the outside of the bag as necessary to get rid of any moisture.
Ask students:
What do you see?
What is happening to the ice?
Why is this happening to the ice?
What do you think is happening to the amount of ice?
Allow the solid to completely change to a liquid, and have students wipe the bag and weigh it again. If time allows (and there is a freezer available), put the baggies into the freezer to solidify the liquid. Then wipe the bags and weigh them a final time.
Ask students:
Does the amount of water change when it changes from a solid (ice) to a liquid?
Does the amount of water change when it changes from a liquid to a solid?
Imagine that a younger friend has just told you that the amount of ice is gone because she saw it melt.
How would you explain her mistake to her?
How would you explain what you observed to someone who did not perform this experiment?
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