# Chemistry

#### Lab: Gas Volumes

Laboratory Exercise

Goal: To show that gas volumes vary with temperature.

Materials:

• Balloons, at least three.
• Stringhttps://www.dorthonion.com/drcmcm/CHEMISTRY/Lessons/Lectures/10a_GasLaw_Units.php
• Buckets large enough to hold the blown-up balloons.
• String
• Pen or felt tip marker
• Yardstick or meter stick
• Ice
• Hot water

Procedure:

1. Blow up three balloons — but do not over-inflate them. Leave room for them to expand with heat. Let them sit for 10 minutes to come to room temperature.
2. Determine the current room temperature and record it.
3. Measure the circumference of the balloon by wrapping a string around its widest part. Mark the position of the string on the balloon, so that when you re-measure, you will use the same circumference.
4. Fill one of the buckets with hot water. Be careful during this procedure not to scald yourself; water of about 110 degrees Fahrenheit (warmer than bath water, but not scalding) is sufficient to create volume differences compared to room temperatures of 68-72 degrees.
5. Using your thermometer (if the water isn't too hot, you may be able to use a normal fever thermometer), measure the temperature of the water before AND after each immersion in the next step. Remember that the water will be cooling off; you cannot assume that the temperature will be the same for all measurements.
6. Place each balloon in the hot water for 2 minutes, remove and immediately remeasure the circumference. Record your observations of the hot water bath temperatures before and and after immersion, and the circumference measured, for each balloon.
7. Fill the bucket (or another) with water and ice. Make it slushy enough to completely submerge to balloons without pushing them against hard ice cubes.
8. Repeat the observations you made in the hot water bath with each balloon, using the cold water bath.
9. Determine the volumes occupied by the balloon at room temperature, hot bath, and cold bath temperatures. Assume that your balloons are perfectly spherical, and remember that circumference is related to radius by C = 2*pi*radius, and the volume of a sphere is related to its radius by V = 4/3 * pi * radius**3.
10. Plot your volumes vs. temperature on a graph (volume on vertical axis, temperature on horizontal axis).
11. Explain how you would increase the accuracy of your measurements and fill in questionable areas on your graph.

Your lab report should include an account of your procedure, all your temperature and raw measurements of circumference, and your calculations of volume; your graph and your suggestions for improving the accuracy of the lab procedure.