Physics

When a parked car is sitting in a sunny location, the interior can get very hot. The Sun’s radiant energy travels through the windshield to the car’s interior. Inside the car, radiant energy is changed to heat energy. The windshield traps the heat, acting much like the glass walls of a greenhouse.

A new company,"Keep Your Cool," has just opened an office in your community. The goal of "Keep Your Cool" is to design and manufacture a screen that can be stretched across the inside surface of the windshield to keep the interior of a parked car cool.

You will evaluate the best materials to block out radiant energy.

• lamp with 300-watt (W) bulb
• squares of glass
• square of cardboard
• squares of linen, cotton, polyester
• colored plastic wrap
• five 100-milliliter (ml) beakers
• 6 thermometers

1. Create five heat-absorbing "devices" to represent the interiors of cars. For each device, pour 100 ml of water into a 100-ml beaker and insert a thermometer into the water. Place a sheet of glass on top of the beaker.
2. The square of glass represents the windshield of the car and the 300-W lightbulb represents the Sun. Several materials are available for you to test as possible screens.
3. It is important to have control data. Place one thermometer on the table under the light next to the beakers. Record the temperature readings for the control value.
4. Place one piece of material (cardboard, linen, cotton, polyester, and transparent plastic) on the glass plate covering each beaker.
5. Turn on the clock and the light.
6. Take a reading of the thermometer in each beaker and the control thermometer at five minute intervals for 15 minutes. Record the data in the data table.

1. Write a memo to the president of "Keep Your Cool," summarizing the results of your experiment.
2. Heat energy travels through outer space from the Sun to the Earth. Does heat energy also travel through air? How do you know?
3. Does heat energy travel through glass? How do you know?
4. Can heat energy travel through cardboard? How do you know?
5. "Keep Your Cool" has asked your lab group to identify the best fabric for upholstering cars. They want a fabric that does not heat up quickly. Design an experiment that you could perform to meet their request.

1. Answers will vary.
2. Yes. Heat energy travels through the Earth's atmosphere to its surface.
3. Yes. In this experiment, heat from the lamp traveled through the glass.
4. No. Cardboard absorbs and deflects the heat and protects the warming device.
5. Answers will vary. Student might suggest wrapping different types of fabric around warming devices like those used in this experiment, then exposing all of them to the same amount of heat and light.