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Measurement of the Specific Latent Heat of Fusion of Ice

Apparatus:

Insulated copper calorimeter consisting of an inner copper can, insulation and outer can. 250ml beaker, thermometer, ice, cloth, paper towels, hammer, top-pan balance, copper stirrer, bunsen, tripod, heat mat and gauze.

Procedure:

1. Measure the total mass of the DRY inner copper calorimeter and copper stirrer.

2. Fill the can with water so that it is approximately two-thirds full. Remeasure the mass and hence determine the mass of the water.

3. Stir the water and measure the initial temperature.

4. Place the inner calorimeter on the tripod and gauze and gently heat while stirring. Heat until the temperature has risen by approximately 6 Degrees. C. While this is taking place use the cloth and hammer to crush some ice into small pieces.

5. Remove the copper calorimeter from the gauze and place into the insulation and outer can. Measure the new temperature of the water, stirrer and calorimeter.

6. Immediately after this, add a small piece of dried ice (use the paper towels) to the water in the calorimeter. Stir to melt the ice.

7. Continue to add dried ice until the temperature of the water etc. has dropped to about 6×C below the initial temperature at the beginning of the experiment.

8. Note this new temperature. Remeasure the mass of calorimeter, water, stirrer and melted ice and so calculate the mass of ice added.

Theory and calculation:

As the temperature has been made to go equally above and below room temperature (approx.) and as we have insulated the copper calorimeter we can assume that the heat loss and gain from the surroundings can be ignored.

Therefore, the heat energy lost by the copper calorimeter, stirrer and warm water in cooling from the highest temperature (stage 5) to the final lowest temperature (stage 8) should be equal to the heat gained by the ice in being melted at 0×C and having its temperature raised (when liquid) from 0×C to the stage 8 temperature.

1. Calculate the heat energy lost by the copper calorimeter and stirrer from:

Heat energy lost by copper = Mass of copper (stage 1) x SHC copper x Temperature drop (stage 5 - stage 8)

Note:

2. Calculate the heat energy lost by the warmed water from

Heat energy lost by warmed water = Mass of water (stage 2) x SHC water x Temperature drop (stage 5 - stage 8)

Note:

3. Calculate the total heat energy lost by the copper and warmed water; = heat lost.

4. Calculate the heat energy gained by the water formed by the melted ice from:

Heat energy gained by melted ice = Mass of melted ice (stage 8) x SHC water x Temperature rise (stage 8 - 0×C)

5. Calculate the heat energy used to melt the ice at 0×C from:

Heat energy to melt ice = Heat lost (step 3) - Heat energy gained by melted ice

6. Calculate the specific latent heat of ice from:

Heat energy to melt ice = Mass of ice (stage 8) x Specific latent heat of ice

7. The accepted value of the latent heat of ice is 336 kJ / kg.

Discuss why your answer is different from this.

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