Frosty Fun: Can we make water change state? 4.5B Physical Engage Students must know… O How to observe and record changes in the states of matter caused by the addition or reduction of heat. Gather the materials: O Soda can (per group) O Water (per group) O Salt (per group) O Crushed ice (per group) O Stir stick (per group) O Plastic spoon (per group) Set the scene O Show a soda can. O Explain to students that they will be mixing salt and ice inside the can to see what happens. Explain the set up O Say: O We are going to try to make water that is in the air change state. Right now around us it is a gas – water vapor. What other states can it turn into? Get students thinking… O Brainstorm some ways that studenst have seen water change state: O Boiling water on the stove O Freezing water in the freezer O Melting ice in iced tea Identify how water has changed state. Demonstrate the set up 1. Put 5 tablespoons of salt into the can. 2. Add crushed ice to fill the can half way. 3. Stir the salt and ice mixture with the stir stick. 4. Observe what happens. Students will observe the changes: O Frost will form on the bottom half of the can (where the salt and ice mixture is). O Water vapor changes directly to solid ice. O Ask: O Why did we see that happen? Explain what happened Frost forms because the ice and salt mixture is very cold, and cools the can enough so that the water vapor contacting the can freezes without ever going through the liquid state of water. Notice no frost forms on the upper part of the can.