Thermal Energy Transfer

Student Sheets

Background

NASA spacecraft and instruments need to be designed by thermal engineers for safe travel into planetary orbit and beyond; "Spacecraft Blankets" are built for long-term durability and high thermal requirements to keep the spacecraft at room temperature.

Different materials need different amounts of heat to produce similar changes in their temperatures. Materials have different specific heats. The specific heat of a material is the amount of energy it takes to raise the temperature of 1 kilogram of the material 1 degree Celsius. Specific heat is measured in joules per kilogram per degree Celsius (J/kg X degrees C). Jumping into a cold pool can take your breath away on a hot day because the water can take heat away from your body more quickly because its specific heat is much higher than that of the air.

Specific heat can be used to measure changes in thermal energy by using the equation:

Change in thermal energy = mass x change in temperature x specific heat

Q = m x delta T x C_p

The equation used when two substances are mixed:

m x delta T x C_p = m x delta T x C_p

Materials

• Calorimeter
• 80- to 100-gram metal sample (like copper weight lead sinker, and aluminum foil)
• One 50-mL beaker
• One 250-mL beaker
• One 400-mL beaker
• Thermometer in degrees C
• Hot plate
• Water
• Goggles
• Balance
• One 100-ml graduated cylinder
• Tongs or test tube holder
• One large test tube

Procedure

1. Add 250 mL of water to a 400-mL beaker.
   
   
2. Place the beaker on a hot plate. Heat the water to a gentle boil. While the water is heating, proceed to step 3.
   
   
3. Determine the mass of a clean, dry 50-L beaker.
   
   
4. Add between 80 to 120 grams of a metal. Measure the mass of the beaker and the metal.
   
   
5. Transfer the metal to a large, dry test tube. Be careful to pour the metal slowly into the test tube so that the test tube does not crack.
   
   
6. Place the test tube inside the beaker so that the metal is below the level of the boiling water bath. Leave the test tube in the hot water bath for 10 minutes. Proceed to the next step while the metal is heating.
   
   
7. Measure out 100 mL of distilled water in a graduated cylinder, and pour the water into the inner container of the calorimeter. Place the thermometer in the calorimeter. Record the temperature of the distilled water.
   
   
8. After the metal has been heating for at least 10 minutes, record the temperature of the water in the beaker.
   
   
9. Assume the temperature of the metal is the same as that of the boiling water.
   
   
10. Remove the test tube from the bath using tongs or a test tube holder. Carefully, but quickly, pour the metal into the water in the calorimeter. Put the top on.
    
    
11. Watch the thermometer to note a temperature change. Record the maximum temperature reached.
    
    
12. Pour the water off the metal. Dry the metal, and return it to the appropriate container.

Data Tables

SPECIFIC HEAT CHART

Questions

1. Calculate the changes in temperature of the water and the metal.
   
   
2. Calculate the heat gained by the water.
   
   
3. Remembering that the heat gained by the water is equal to the heat lost by the metal, calculate the specific heat of the metal.
   
   
4. Using the accepted value given in the table below, calculate the percentage of error in the specific heat value that you determined experimentally.
   
   Percentage of error = accepted value - experimental value divided by the accepted value x 100
   
   
5. What could account for any sources of error?
   
   
6. How much energy is required to heat 150 mL of water from room temperature (20ºC) to 84ºC?
   
   
7. How much energy is required to heat 10 grams of silicon from 22 ºC to 44 ºC? (specific heat = 0.181 cal/gºC)