In previous activities you heated water by converting electrical energy to thermal energy in an immersion heater and then transferring this heat to water by conduction. In this activity you will transfer heat from a heat lamp by radiation and explore the different factors that affect the rate of heat transfer. Complete this lab in your lab notebook, making sure to attach this sheet, carefully record and label all data, to answer all questions and discuss your results.

In this activity you will investigate how the rate of absorption of heat depends on the nature of the surface. Before you start make a prediction: What type of surface would absorb heat at a faster rate – a silver surface or a black one?

1. Fill the silver can with room temperature DI water and place the can on top of an upturned Styrofoam cup to minimize conduction through the bottom of the can. (Make sure to record the mass of water you are using.)
2. Place a temperature probe in the can, keeping it off the bottom.
3. Set up the heat lamp about 35 cm from and aimed directly toward the can. Shield the top of the probe and wire from the heat lamp using a piece of paper.
4. Start measuring the temperature, then turn on the heat lamp and record for five minutes. Record the initial and final temperatures in an organized table in your notebook.
5. Repeat the above procedure using the darkened can. Make sure you use the same amount as water as you did for the silver can.

1. What was the temperature change in each case?
2. How much heat was absorbed by each can?
3. What is the rate at which heat was absorbed by each can?
4. Which can absorbs heat at a faster rate?
5. Which surface would emit heat at a faster rate? – How would you test your predictions?

Discussion:

Dicuss any errors in or limitations of your results.

In this activity you will investigate how the rate at which thermal radiation is absorbed depends on distance.

1. Repeat the procedure above using the black can recording the increase in temperature when the heat lamp is placed at four or five different distances from the can. (make sure you use the same amount of room temperature water in each case). Think carefully about choosing a suitable range and spacing of distances – what might be too close what might be too far? Explain why you have chosen the particular distances you choose. Your data should be carefully arranged in a well organized data table.
2. For each distance determine the rate at which heat is absorbed by the can.
3. Plot the heat absorption rate versus distance in your lab notebook. Create a suitable power fit to your data and record you fit in your note book. (You can do this on your calculator, by using excel or by using the Logger Pro software)
   

1. How does the heat absorption rate vary with distance from the heat source?
2. What other variables could you vary that might influence the heat absorbtion rate besides the colour of the surface and the distance from the source?