WLHS / Chem / Monson / Unit 7 – ThermochemName

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LAB: HEAT OF FUSION OF ICE

The amount of energy required to convert one gram of a solid, at its melting

point, to a liquid is called the heat of fusion of the substance. In this activity,

the heat of fusion of ice will be determined experimentally. The ice will be melted by placing it in a known volume of hot water contained in a plastic foam cup. The system will be left undisturbed until all the ice has melted. Using the mass of the ice melted (calculated from volume and density) and the heat absorbed by the ice (calculated from change in temperature and specific heat capacity of water), the heat required to melt one gram of ice can be calculated. The heat lost by the water will be absorbed by the melting ice.

Heat gained by ice = Heat lost by the water = mH2O  cH2O  TH2O

Equipment

250 mL beakerhot plate

plastic foam cup with lidgraduated cylinder

400 mL beakerthermometer

plastic spoonice

Procedure

1) Add approximately 100 mL of tap water to a 400 mL beaker and heat the water to 60oC, using a hot plate. While the water is heating, fill a Styrofoam cup halfway with ice cubes. Place the cup in a 250 mL beaker for support.

2) When the temperature of the water has reached 60oC, use two 20 mL portions of this hot water to preheat a 100 mL graduated cylinder. Rinse the cylinder with each of the hot water portions and discard the rinses.

3) Pour 30 mL of the hot water into the graduated cylinder. Record the volume of this water to the nearest 0.1 mL. Measure and record the temperature of the water to the nearest 0.1oC.

4) Quickly drain any excess water from the ice cubes in the cup. Add the measured hot water to the ice in the cup. Stir the ice water rapidly (but carefully) until its temperature falls to 2oC. At this point, some unmelted ice should remain in the cup. If, in fact, all the ice has melted, add a bit more so that some ice remains unmelted when the temperature is 2oC or below. Record the lowest temperature of the mixture of ice and water to the nearest 0.1oC.

5) Using a plastic spoon, quickly remove any unmelted ice from the cup. As you remove the ice, drain as much water as possible back into the cup.

6) Carefully pour the cold water from the cup into the graduated cylinder and record the final volume to the nearest 0.1 mL.

Data Table

volume of hot water (mL)
initial temperature of hot water (°C)
final temperature of water and melted ice (°C)
final volume of water and melted ice (mL)

Data Analysis:

1) Calculate the change in the temperature of the hot water.

2) Calculate the mass of hot water. (Density of water = 1.0 g/mL; D = mass/Volume, so mass = DV)

3) Calculate the heat lost by the water. (which is equal to the heat gained by ice)

H (heat lost by water) = mass H2O  c H2O  T H2O = H (heat absorbed by ice)

4) Calculate the volume of ice melted.

5) Calculate the mass of ice melted. (Density of water = 1.0 g/mL; D = mass/Volume, so mass = DV)

6) Calculate the heat of fusion (Hfus)of ice in joules per gram (J/g).

Hfus = H (heat absorbed by ice)

mass of ice melted

7) Calculate the percent error in your determination of the value for the heat of fusion of ice.

(accepted value = 333 J/g)

Conclusion Questions:

1) In order to do the calculations, you assumed that all the heat lost by the hot water was absorbed by the ice, causing it to melt. Was this assumption correct? Explain your answer.

2) Write a chemical equation for ice changing to liquid water. Include the energy term in J on the proper side of the equation.

3) Why preheat the graduated cylinder in step 2 of the procedures?