# Guiding Question: How does heat energy affect water and air?

*If you looked at the previous simulation activity, compare what you now know about water to air.

1. Explaining the model. This investigation will use two tightly sealed bottles—one filled with water and one containing air. Both bottles are at room temperature. A lamp will provide heat energy to both bottles equally.
2. Predict what will happen. What will happen to the temperature of the two bottles receiving heat energy? Which bottle do you predict will heat up faster? Do you think water molecules will behave differently than air molecules when heat energy is added? What makes you think that?
3. The simulation. This model is showing what happens to water and air molecules when heat is added. Notice the thermometer inside each bottle, the temperature displays, the sealed bottles, and light bulb (which is off). This simulation is based on scientific evidence about how molecules move. What do you notice? Does the air or the water have more matter in it?
4. Start Simulation. Click “HEAT ON” and take note of the time elapsed and temperature displays. What do you notice?
5. Discuss. Why did the water heat up more slowly than the air? If no one mentions it, share that part of the reason is that water has more stuff in the same amount of space, so it takes more energy to get all the molecules moving more.
6. Introduce the term absorb. Absorb means to take in. Explain that water molecules can absorb a lot of heat energy before they start moving more.
7. Stop Simulation. After 5 minutes click “HEAT OFF”. The timer will continue to run as the bottles cool down. What happens to the air and water molecules when the heat is turned off? [The air molecules quickly slow down, while the water molecules slow over a longer period of time]. What happens to the temperature in the two bottles? [The temperature drops quickly back to starting temperature in the air bottle, and the temperature stays roughly the same in the water bottle]. Continue to watch the simulation.
8. Introduce the term heat reservoir. Scientists call water a heat reservoir because water absorbs a lot of heat energy before it warms up and it holds onto the heat for a relatively long time before the heat energy is released and the water cools down.