# SPECIFIC HEAT AND HEAT OF FUSION

Document Sample

```					Ph202: General Physics II Lab Instructor: Tony Zable

1

Experiment #4: Specific Heat and Heat of Fusion
Preliminary Questions:
1) A 50 gram specimen of iron is heated from room temperature (20oC) to 100oC. How much heat does the iron absorb?

2) If there were twice as much iron, how much heat energy would be absorbed by the sample during the same heating process described in question #1?

3) The hot 50-gram iron sample is then placed into a thermally isolated container with 30 grams of cold water. When the water and iron reach thermal equilibrium, the change in temperature of the water is 10oC. How much heat energy does the water gain? How much heat does the iron lose?

4) What is the final temperature of the water and iron?

5) A 50 gram unknown metal sample (initial temperature of 100oC) is added to 30 grams of water and the two substances are allowed to achieve thermal equilibrium. The initial and final temperatures of the water are 22oC and 35oC, respectively. Determine the specific heat capacity of the unknown metal.

Ph202: General Physics II Lab Instructor: Tony Zable

2

Objective:
  To measure the specific heat of 3 solids To measure the latent heat of fusion of ice.

Theory
The heat absorbed by a substance is related to the change in temperature observed in the substance according to the following relation: heat gained = (specific heat)*(mass)*(change in temperature) or

Q = c * m * T
where the units are Q in Joules, c in J/kgoC, m in kg, and T in oC. The specific heat capacity of a substance is one of its physical properties. Every substance has a unique specific heat. By measuring the specific heat of an unknown substance, the measured value can be compared with a table of known specific heats to determine its identity. The heat required to change the physical state of a substance from solid to liquid water is related to the mass of the substance and the latent heat of fusion according to the following relation: heat absorbed/released = (latent heat)*(mass) or

Q = Lf * m

(where the units are Q in Joules, Lf in J/kg and m in kg)

The latent heat of fusion of a substance is one of its physical properties. Every substance has a unique latent heat. By measuring the latent heat of a substance, the measured value can be compared with published values. Procedure: 1) Weigh the samples and the calorimeter. 2) Place the samples into a beaker containing boiling water. 3) Pour cold water (i.e. whose temperature is roughly as far below room temperature as its final temperature will be above room temperature) into the calorimeter until it is half full. Weigh the calorimeter and water. 4) Measure the original temperature of the water. 5) Quickly transfer the sample (be sure to dry it off!) from the beaker to the calorimeter. Place the top on the calorimeter and insert the thermometer 6) Using the computer based thermometer, set-up LoggerPro to display a graph of Temperature vs. Time. Gently swirl the water to achieve good thermal transfer between the water and the solid. Continue to take temperature readings until the temperature of the water has reaches a maximum value. Record the maximum temperature. Repeat the experiment with 2 additional solids.

Ph202: General Physics II Lab Instructor: Tony Zable
Specimen Mass of specimen Mass of water Initial Temp (Specimen) Initial Temp (Water) Final Temp (Water/Specimen)

3
Specific Heat Capacity (c)

7) Latent Heat of Fusion of Ice: Repeat the experiment above, except ice (dried) is added to the water. The stirrer is used to keep the ice submerged under the water. Weigh the calorimeter and its contents after the experiment to obtain the number of grams of ice added.
Specimen Mass of water Mass of ice Initial Temp (Water) Final Temp (Water) Latent Heat of Fusion (L)

Analysis: 1) Calculate the specific heat of the solids, and the latent heat of fusion of the ice. 2) Compare the results with values found in the tables. Use the CRC to obtain the appropriate table. Determine the % error for your measurements.

Specimen

Calculated Specific Heat Capacity (c)

Calculated Latent Heat of Fusion (L)

Accepted Value (from CRC)

% Error

Ph202: General Physics II Lab Instructor: Tony Zable

4

The Finale: Does the heat absorbed by the inner chamber of the calorimeter affect your final measurements? Recalculate your specific heat values taking into account the heat gained by the calorimeter.

Corrected Values Specimen Calculated Specific Heat Capacity (c) Calculated Latent Heat of Fusion (L) Accepted Value (from CRC) % Error

```
DOCUMENT INFO
Shared By:
Categories:
Stats:
 views: 155 posted: 11/29/2009 language: English pages: 4
How are you planning on using Docstoc?