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Demonstration: Dramatic Demonstration of Thermal Conductivity and Specific Heat Capacity FOR THE TEACHER Summary In this demonstration, students will observe the high thermal conductivity and low heat capacity of copper metal.
Submitted by ACS High School Professional Development Team Washington, D.C.
Grade Level High School Objectives By the end of this demonstration, students should be able to • understand the difference between thermal conductivity and specific heat capacity Chemistry Topics This demonstration supports students’ understanding of • Specific Heat Capacity • Thermal Conductivity • Properties of Matter • Energy transfer Time Teacher Preparation: 10 minutes Lesson: 20 minutes Materials • 20 g of coiled copper wire • 400-mL or 600-mL beaker • Tap water • Hot plate • Thermometer or temperature probe • Tongs Safety • Students should wear proper safety gear during chemistry demonstrations. Safety goggles and lab apron are required. • Exercise caution when using a heat source. Hot plates should be turned off and unplugged as soon as they are no longer needed. • If there are water droplets on the copper wire when you remove it from the boiling water, the water will burn!! • Do not allow students to perform this experiment. Teacher Notes • A video of the demonstration can be found in the download box at the top of the page. • Heat is an artifact of the transfer of energy. For thermal energy transfer, molecules must come into contact with each other. The transfer of energy occurs continuously on a American Association of Chemistry Teachers
particulate/molecular level. On the macroscopic scale, however, we will notice that “Thermal Equilibrium” is reached when the temperatures of the objects are equal. Copper has an exceptionally high thermal conductivity, but a very low specific heat capacity. o Thermal conductivity is a measure of how well a substance conducts heat. The higher the thermal conductivity, the greater the rate of heat transfer. Since copper has very high thermal conductivity it will release heat quickly. o Specific heat capacity if a measure of how much heat is needed to raise the temperature of a substance. Typically, it is the amount of heat (joules) required to raise the temperature of one gram of a substance by one degree (°C). Since copper has very low specific heat capacity it requires very little energy to raise its temperature. Copper will change temperature very quickly when it is removed from the water. Some of the energy is lost to the air in the transfer AND when the copper touches your hand, the energy needed to lower the temperature of the copper is very low, due to its low specific heat capacity. Meaning, that not much energy is transferred to your hand, and risk of burning your hand is very low. Additional background information about specific heat capacity, heat transfer, and thermal conductivity can be found in a separate document for download.
Procedure 1. Place 20 grams of coiled copper wire into a beaker of water, making sure that the water completely covers the wire. Be sure to allow for evaporation. 2. Heat the beaker and contents on a hot plate, until the water comes to a rolling boil. 3. Allow the contents to boil for 5-8 minutes. 4. Record the temperature of the water. 5. Ask students what they think the temperature of the copper wire is. • If they have the opportunity to work with Ice Melting Blocks, they should be able to agree that the temperature of the copper is the same as the boiling water. • See the lesson plan “What Makes Something Feel Warm? Modeling Energy Transfer” to find out more information about using Ice Melting Blocks. 6. Using tongs, remove the copper wire from the boiling water, and quickly shake off the excess water droplets. 7. Place the copper in your hand.