Heat of Fusion of Water
According to the kinetic molecular theory, all molecules are in constant random motion. Temperature is a measure of
the average kinetic energy per particle of a substance. The specific heat of a substance is the energy in joules
required to raise the temperature of one kilogram of a material one Kelvin (or to raise the temperature of 1 gram of the
material one degree Celsius). The specific heat of water has been determined to be 4.18 J/g- C.
In this lab, you will determine experimentally the heat of fusion of water. Energy released by warm water will be
absorbed by pieces of melting ice. The melted ice will then rise in temperature until the melted ice and the original
water reach an equilibrium temperature. Ice requires 334 joules per gram to liberate particles from its crystalline
matrix.
Purpose: To determine the heat of fusion of water.
Procedure:
1. Heat beaker of water to approximately 40 °C.
2. Pour about 35 mL of warm water from beaker into graduated cylinder. Record volume on data table.
3 . Cover the cup with the lid, insert the thermometer into the cup through the opening in the lid and record the
temperature of the water to n e a r e s t 0 . 2 °C. Turn the thermometer off.
4. Obtain 3 pieces of ice and blot the surface of the ice dry with a paper towel. Carefully place these ice cubes
into the cup and replace the lid.
5. Gently shake the cup to stir the ice and the water mixture, occasionally removing the lid to see if the ice has
melted. Do not remove the lid too often in order to reduce loss of heat.
6. Continue shaking and adding ice in order to allow water and ice mixture to equilibrate to 0 °C and excess ice
remains.
7. Pour liquid water into a beaker by straining with lid to hold back ice remaining.
8. Pour beaker of water into graduated cylinder and record volume of water.
9. Repeat steps (1-7) for Trial II.
10. Follow clean up procedures as stated on board.
11.
Data Table: Create the data table below in your notebook for your lab write-up.
Trial I
Trial II
Volume of water used (mL)
Initial Temperature of Water (mL)
Equilibrium Temp. of Ice/water (°C)
Final Volume of Water (mL)
Mass of Ice melted (1g water = 1mL water)
Change in Temperature of Water (°C)
Energy released by water as it cools (J)
Joules required to melt 1.0 g of ice (J)
Kilojoules required to melt 1.0 mol of ice (KJ)
% error (experimental-accepted/accepted X 100)
Processing Data: Use the information below when answering questions from the data analysis
section below.
1. Calculate:
a. The mass of warm water you started with.
b. The mass of ice used.
c. The change in temperature of the warm water.
d. The change in temperature of the ice (assume it was at 0 C initially).
2. Calculate the energy lost by the warm water: Energylost = (mass) x (4.18 J/g°C) x ( T water)
Make sure your answer includes units.
3. Remember that the energy lost by one substance is gained by something else. The energy lost
by the warm water was used to do two things: 1) melt the ice, and 2) warm the cold water that resulted when
the ice melted. Calculate the energy used to warm the water that formed when the ice melted.
Make sure you use the mass of the ice in this calculation.
Energy = massice x (4.18 J/g °C ) x ( Tice)
4. The difference in energy calculated in step 2 and step 3 above is the energy used to melt the ice. Use
this energy and your value for the mass of ice to calculate the heat of fusion of water.
EnergyStep 2 - EnergyStep 3 = (mass of ice) x (heat of fusion)
5. Calculate your percent error from the accepted value (334 joules/gram).
6. Write your conclusion. Include a summary of your results and your analysis of sources of experimental error.
Data Analysis: Use the data processing help to answer the following questions and accurately calculate using data
from your experiment.
1. Determine the mass of ice melted (the density of water is 1g/mL).
2. Determine the change in temperature of water.
3. Calculate the energy released by the liquid water as it is cooled in Joules.
4. Calculate the Joules of energy required to melt 1 gram of ice? The specific heat of water is 4.18 J/g °C
5. Using the results of this experiment, determine the number of kilojoules required to melt one mole of ice (1000J
= 1 KJ)
6. Use chemical symbols in writing an equation for the fusion (melting) of ice, and include the energy term (in
KJ/mol of water) as calculated n question 5.
7. Calculate the experimental percentage error by comparing the experimental value which you have determined
for the heat of fusion of ice to the accepted value for the heat of fusion (6.010 KJ/mol)