Heat Transfer

1. Heat Transfer Part I: Temperature and Thermal Energy Transfer What is temperature? What is thermal energy? How does the temperature of the ice chip compare to the temperature of your hand? In the example of holding ice, what evidence indicates that thermal energy transfers? In the example of holding ice, where does the thermal energy come from? In the example of holding ice, where does the thermal energy go? Using the example of holding ice, explain when the thermal energy transfer stops. Can you summarize how thermal energy moves from one object to another? Thermal energy always moves from substances with __________________temperatures to objects with ___________________________ temperatures. 1

2. Heat Transfer • Part II: Conduction • Rub your hands together as fast as you can for 30 seconds. Record what happens. • Observe the demonstration at the front. Use the drawing below to illustrate what you observed. Use labels and arrows to identify the transfer of energy. • What type of heat transfer occurs along the aluminum foil? • What pattern was evident in the movement of thermal energy? • What evidence did you observe that showed heat transfer. • In your own words, define conduction. 2

3. Heat Transfer Part III: Convection • Draw a lava lamp and show what happens to the blob you observe. Use arrows and labels to identify the parts of the lamp and the heat transfer. Drawing should show blob moving to the top and then sinking. Be sure students realize this is a convection current where the blob is heated at the bottom and begins to rise. When the blob cools it begins to sink. • Draw the can of cooking fuel and what you observed on the wall or board. Use arrows and labels to identity the set up and the heat transfer. Be sure to show where the heat near the ceiling went. Drawing should show the can and heat waves in the shadow. Be sure students realize that even though we can no longer see the heat waves, they are still there. The heat waves have cooled off and are sinking toward the floor again setting up a convection current. • In which state of matter did the transfer of thermal energy occur in the lava lamp? Liquid. The rising heated blob mixed with the cooler liquid in the glass container. • In which state of matter did the transfer of thermal energy occur when you observed the cooking fuel? Gas. The rising heated gas mixed with the cooler gas in the room. • When observing the cooking fuel demonstration the shadow eventually disappeared. What happened to the heat in this system? Even though we can no longer see the heat waves, they are still there. The heat waves have cooled off and are sinking toward the floor again setting up convection currents. • In your own words, define convection. Answers will vary but should include direction of heat transfer, states of matter in which convection occurs, density differences are the cause. 3

4. Heat Transfer Part IV: Radiation • Record your data in the boxes below. • Graph the ending temperatures for each location of the radiometer. • Fill in the blanks using the data you recorded. • As the distance increased the temperature decreased. . • As the distance decreased the temperature increased. • In your own words, define radiation. Answers will vary but should include travels by electromagnetic rays, no matter is needed. 4

5. Heat Transfer Reflections and Conclusions Identify the type of energy transfer (conduction, convection, or radiation) for each description below. 5

6. Heat Transfer Reflections and Conclusions • When particles of matter are in direct contact, conduction of thermal energy occurs in which states of matter? Solids, liquids, and gases. • When particles of matter are in direct contact and movement occurs in the substance due to convection, thermal energy transfers in which states of matter? Liquids and gases. • Which states of matter are required for energy transfer to occur when radiant energy is the source? Matter is not required for energy transfer by radiation. • Use your data from Part II to draw a conclusion: In thermal energy transfer by conduction, how does heat move between objects that are touching? The part of the object touching the thermal energy source heats up first. The heat moves through the touching particles in the object, until the entire object reaches the same temperature. • Use your data from Part III to draw a conclusion: In thermal energy transfer by convection, what is the pattern of heat transfer through fluids?  As the particles are heated, the warmer, less dense fluid begin to rise, and cooler, denser particles sink to take their place. This pattern continues until all of the particles of the gas or liquid reaches the same temperature. • Use your data from Part IV to draw a conclusion: In thermal energy transfer by radiation, how does distance from the thermal energy source affect the amount of thermal energy transfer occurring in a substance? The farther an object is from the thermal energy source the less energy transfers by radiation. 6