Beacon Lesson Plan Library

Insulators, Conductors, and Energy Transfer

Carol Houck

Description

Students conduct experiments to determine what types of material make good insulators.

Objectives

The student knows the processes by which thermal energy tends to flow from a system of higher temperature to a system of lower temperature.

Materials

- Two test tubes
- Two test tube stoppers (one hole)
- Two thermometers
- Lubricating oil
- Assorted fabric materials
- Science journals
- Tape or rubber band

Preparations

- Thermometers should be lubricated and inserted carefully through the test tube stoppers prior to the class experiment.
- Each group will receive two test tubes.
- Assorted materials (cotton, wool, felt, polyester) should be cut in equal squares and labeled. Each piece should be big enough to go around a test tube twice.
- Prior to class, the facilitating teacher may perform the following demonstration:
Fill two identical glass, large mouth bottles or jars with water. Pour cold water containing a dye in one jar. Pour warm water in the other jar. Place a piece of cardboard over the jar of cold water. Over the sink, invert the jar with cold water over the jar with warm water. Line up the tops and pull out the cardboard. The cold water will sink and the warm water will rise. A thermal gradient is demonstrated as the cold, dyed water sinks and the warm water rises.

Procedures

Knowledge and Skills:
- Students will be able to illustrate conduction and convection and explain the processes of heat transfer.
- Students will be able to define conductors and insulators and identify commercial uses for each.
- Students will be able to determine which types of fabrics would be appropriate for different types of clothing (a winter coat vs. a summer shirt).
- Students will design other experiments to determine the conductive abilities of other types of materials (glass, iron, plastic, etc.).
- Students will be able to analyze temperature vs. time graphs.
- Students will determine which materials would be best used for an Arctic expedition.

Procedure:
1. Divide students into groups of two or three.
2. Have students fill both test tubes with hot tap water of the same temperature. Have students secure the stoppers with thermometers in the test tube.
3. Assign a square of material to each group; direct them to wrap one test tube with the material. The material should be secured with tape or a rubber band. The other test tube is left without material. This test tube will serve as the control.
4. Have students record the initial temperatures of both test tubes.
5. Direct the students to prepare a data table and to record the temperature of the water in both test tubes every minute for a total of thirty minutes.
6. Have students prepare a graph of time vs. temperature for their sample.
7. Choose a graph using each kind of material to display for class analysis and discussion.

Assessments

Assessment questions may include the following:

1. Which of the following statements is true about the flow of energy:
a. Energy does not flow
b. Energy flows from hot to cold
c. Energy flows from cold to hot
d. Energy is not conserved

(answer b. Energy flows from a system of higher temperature to a system of lower temperature.)

2. Based on your observations, which of the following processes accounts for the change in temperature in the test-tube?
a. Conduction
b. Convection
c. Both a and b
d. None of the above

(answer c. Conduction and convection both play important rules in the transfer of energy.)

3. Wrapping the testtube several times with a material may help it stay warm due to a decrease in what process?
a. Conduction
b. Convection
c. Radiation
d. Transmutation

(answer a. Direct contact flow of energy is conduction.)

Energy transfer may take place via many modes; however, most common to the transfer of heat is conduction and convection. Conduction is the transfer of energy through direct contact while convection uses air and space between objects to promote the flow. In either case, energy is transferred by the passing along of the energy from one molecule to another until the energy has been completely dissipated. Objects with tightly packed molecules are able to transfer energy more easily than those with greater spaces. For this reason, conduction through direct contact may be more efficient than convection which uses air and space.

Objects which allow for the transfer of energy are called conductors, those which do not are called insulators.

Extensions

Enhancements:
Other experiments might include measuring the effects of different gasses, or the complete lack of, on the rate of convection, or testing materials such as wood and plastic.
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