Objectives | Materials | Invitation to Learn | Lab Procedure | Closure

After investigating the effect of temperature changes on a confined gas, students will be able to:

1. Relate the changes in volume of gases to changes in the temperature (i.e. direct relationship).
2. Explain why the volume of a gas increases as the temperature increases.
3. Predict the volume of a gas when its temperature is specified.
4. Optional: Construct a mathematical expression for the relationship between pressure and volume (i.e. P x V is always equal to a constant value dependent on temperature).

Preliminary Knowledge:

1. Basic math skills and some simple algebra
2. Graphing skills
3. Familiarity with the principle of the particulate nature of matter (a concept presented in the 7th grade Science Core Standards)
4. The natural motion of particles in matter
5. Common units of measurement for volume such as liters (L) and units for pressure such as mm Hg or atmospheres (atm)

• Computer Lab with Internet connection or a single machine and suitable projection equipment. We recommend a Pentium class computer (166 MHz, with at least 32 MB ram).
• Java-capable and enabled browser with the Java plug-in installed. For questions/assistance write <support@cosmic.utah.edu>.
• Calculator
• Lab notebook or Student Packet - This is a printable version of the lab materials (instructions, tables, questions, graph formats, and questions/problems) where students can record their lab.

1. Inflate two balloons and place one in a cooler and the other in a warmer environment. Ask students what happens to the volume of the balloon when it is warmed? What happens to the volume of the balloon when it is cooled. Ask students what variable is being changed?
2. Partially fill a plastic one or two liter bottle with hot water and cap it tightly. Immediately put the bottle in a cooler with dry ice and close the cooler lid. Several minutes later, remove the bottle. The bottle should have collapsed due to the cooling of the gas inside and the slowed molecular movement. Ask students why the bottle collapsed? What would the change in temperature have done to the gas inside the bottle? What happened to the volume of the gas inside the bottle?
3. Have students work in groups to list other everyday examples of how the heating or cooling of gases affects volume.

Pre-Assessment:

Here are several questions which will gauge your students' understanding of the effect of temperature changes on the pressure of confined gas.

1. Note that this is the scenario used in the student lab: Suppose you are in a warm store buying helium balloons for your friend's birthday. As you walk home on that cold day, you notice the balloons are not as big as they were in the store and they aren't floating as high. Why is this happening?
2. What is the relationship between gas temperature and gas volume?

Directions for teaching the lab:

1. Have students proceed to the beginning of the student lab. Students should first read the introductory statements and other information that pertains to the lab. Have students list their variables and make their predictions before running the lab.
2. As students scroll to the gas container they will notice that it is shaped differently than ones in the previous labs. This container is a sliced-section of a capillary tube with a plug of mercury. The mercury plug seals off the air in the tube from the surrounding atmosphere and keeps the pressure inside the tube constant.
3. The default values for the volume and temperature will already be recorded in the data table.
4. Students will also see gas particles moving randomly and at a constant velocity inside the capillary tube.
5. Temperature can be changed by clicking on the thermometer and dragging to the desired setting. At the selected temperature, the students will observe the volume of the gas change by seeing the mercury plug move up or down the capillary tube.
6. Remind students to record the data into their notebooks.
7. After testing several temperatures, students should continue to the graphing and analysis sections of the student page. They may return to collect additional data by scrolling back to the gas container.

Special note to teachers: It is very important that students attempt to graph their data by themselves before using the hints that are provided at the end of the student pages.

Summary:

It is expected that after completing the activities and analyzing the data that students will discover:

• There is a direct relationship between gas temperature and volume at a given pressure (as the temperature of a gas increases, so does its volume).
• Why an increase in temperature causes an increase in volume.
• That gas particles are in constant motion and that the motion increases with temperature.
• OPTIONAL: There is mathematical relationship between volume and temperature (V/T is always a constant).
• OPTIONAL: When values for V and T are given and conditions are changed, the corresponding values for T or V can be calculated by using the formula V1/T1 = V2/T2.

Students should be encouraged to make connections from this lesson to some common events in their own lives.

• 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 degrees F"?
• Why does a car tire's pressure increase during summer months?
• Why do car or bicycle tires seem under-inflated in winter months?
• Explain how the "egg in the bottle" trick works. (Remember we can get a hard-boiled egg to enter a large gallon jug if we first heat the air in the jug, place the egg on the mouth of the jug as a seal, then cool the gases inside by spraying cool water onto the jug.)
• Explain the bumping of a lid on a pot of boiling water.

Post-Assessment:

Teachers may return to the pre-assessment questions and use these same questions or construct their own post-assessment instrument. Hopefully, teachers can also include more difficult, higher-level questions in their post-assessment.

Extension activities:

• Have students return to the balloon scenario given in the lab. Have them design a balloon that would not be affected by temperature changes. What could be done to the balloon before it leaves the store to ensure it does not lose any volume? You can even have the students go into the topic of density and explore the fact that when a helium balloon's volume decreases, the density will increase and the balloon will not float as well.

• Student groups can run a balloon lab in which the lab group has a partially filled rubber balloon and places it in containers of differing temperatures. The groups then measure the size of the balloon and graph their data.

• A demonstration would be to place partially inflated balloons into a container of liquid nitrogen. The balloons will "deflate" and then "re-inflate" once removed and given time to warm.