• Relate the changes in volume of gases to changes in the temperature.
• Explain why the volume of a gas increases as the temperature increases.
• Predict the volume of a gas when its temperature is specified.

Materials Needed: balloons, helium, freezer, heater

1. As a group, inflate two balloons with helium. Measure to see that they are the same size. Ask the students to predict (in writing) what they think will happen to each balloon.
2. Place one balloon in a freezer. Place the other balloon in a very warm place (near the heater or outside on a very hot day).
3. Take the balloons out and measure to see if the prediction was accurate.
   

Materials Needed: balloons, helium, freezer, heater, plastic bottle, dry ice, cooler

1. Partially fill a plastic two-liter bottle with hot water and cap it tightly.
2. Immediately put the bottle in a cooler with dry ice and close the cooler lid.
3. Have the students predict in writing what they expect to happen.
4. After a few minutes, take the bottle out of the cooler. (The bottle should have collapsed due to the cooling of the gas inside and the slowed molecular movement.)

With a partner, write a paragraph addressing the following questions:

1. Why is the following warning placed on most spray cans: "DO NOT place in hot water or near radiators or stoves. DO NOT incinerate, even when empty. DO NOT store at temperatures above 120° F."
2. Why does a car's tire pressure increase during summer months?
3. Why do car or bicycle tires seem under-inflated in winter months?

The following rubric will be used to evaluate the writing.

This activity was written by Meghan O'Leary & Jaci Kottman.

Students will make a graph using data gathered in the balloon experiment.

6 balloons for each group (same size balloons), helium, thermometers

1. Put students into groups of two or three.
2. Students will blow up four balloons, making sure the circumference is the same on each balloon.
3. The four balloons will each be placed in a different location, each at a different temperature, for 15 minutes. Put a thermometer with the balloon so that the temperature can be noted.
4. The circumference will then be measured and graphed.

   a. The graph will be a double line plot with temperature on the x axis and size on the y axis.

   b. A line for the original circumference measurement should be displayed. A second line showing the circumference after changing the temperature should be drawn.

5. Follow the same procedure using helium as the inflating gas.
6. Using the same graph, display a third line in a different color that shows the circumference after changing the temperature.
7. Students will write an explanation telling what the graph shows them. They should use numbers in their explanation.

The following rubric will be used to evaluate the graphs.

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