Activity Overview: Before the advent of modern air conditioning, snow and ice were the main ways to keep cool on hot days. In the summer and in warmer climates, ice was a luxury used to cool drinks and cool bodies in the same way refrigeration and air conditioning are used today.
The melting of the frozen water and the evaporation of the liquid water provides the cooling effect. As the water absorbs heat energy from the environment, it cools down the surrounding air. This is the same process that occurs in a modern air conditioner. As the refrigerant evaporates in the lines, it absorbs heat from the air blowing over the evaporator coil.
Materials: bowl of ice, desktop fan
Without the technicalities of refrigerant and a high pressure system, you can mimic this process in your classroom with a bowl of ice and a simple fan. Even if your classroom is at a comfortable or cool ambient temperature, ask students to feel the temperature difference created by fast moving air from the fan. Then, place the bowl of ice in front of the fan and let it run for several minutes. Now, ask students to feel the temperature difference created by the melting ice. Depending on your ambient temperature, it might be a very slight change. If possible, repeat this activity outside on a warm day. Do your students feel the change now?