Measuring the Latent Heat of
Fusion of Ice
Object of the Experiment
Energy is required to change water from a solid to a liquid, i.e.
to melt ice. In this experiment you will try to measure the
latent heat of fusion of
needed (per gram) to melt ice. The needed energy will come from a
cup of warm water. The amount of water and its temperature will
be measured before adding some ice and then again after the ice
has been melted. These data will be used in an energy balance
equation to determine LHice.
Conducting the Experiment
You will first need to obtain some ice. Let the ice sit in
a bowl at room temperature until you notice that it is starting to
melt. This will probably take 15 to 20 minutes. In a
freezer, ice is kept at a temperature well below freezing (typically
near 0o F). We need to allow the ice to sit outside
the freezer long enough that is warms up to freezing (0o
C or 32o
F). The ice can't get warmer than freezing; once it reaches
freezing it will start to melt.
Add 200 to 250 mL of warm tap water (40o
C or less so that there isn't too big of a temperature
difference between the water and air) to the styrofoam
cup. We keep the warm water in a styrofoam cup to
minimize the loss of heat to the cooler surroundings. Keep a
record of the actual amount of water added to the cup. Measure
and record the temperature of the warm water just before you are ready
to add some ice.
Add one or two ice cubes (or about 1/4 cup of crushed ice) to the warm
water and stir gently with the thermometer until the ice is completely
melted. Try to be sure you just add ice and none of the water
in the bowl from the melted ice. Once the ice in the cup has
melted, measure and record the water temperature. If the
temperature has dropped to near freezing or if you are unable to melt
all of the ice, you will need to repeat the experiment. You will
need to use less ice or more water or both.
Use the graduated cylinder to measure the new volume of the water in
the styrofoam cup. This new volume will be larger than the
initial volume because it contains the water from the melted ice.
Because water has a density of 1gram/mL (1 gram/cm3) there is a one to
one relationship between a measurement of water volume in mL and the
mass of the water in grams. The difference in the starting and
ending water volumes is the mass of the ice that was melted.
Repeat the experiment at least one more time using a different amount
of water, a different amount of ice, and perhaps a different initial
The conditions at the start of an actual trial run of the
experiment are shown below. Tinitial is the temperature of the
water water before the ice was added, Mwater is the mass of the warm
water (note the mass is actually determined by measuring the intial
volume of the water). We assume that the ice has an initial
temperature of 0o C because we let
the ice sit at room temperature until it had started to melt.
In the figure below the ice has
been added to the warm water and melted. We are at the "midway"
point of the experiment; the ice has turned from a solid to a liquid
but its temperature hasn't changed, it is still 0oC.
The energy needed to melt the ice
This energy came from the warm
water and cause the water to cool (from Tinitial to Tmid). We
could use the following equation to determine how much energy was taken
from the water (we won't do the calculation because we don't know what
Heat will continue to flow from the
warm water into the 0o
C ice water. Energy will flow until all of the water
has the same temperature, Tfinal.
So the warm water will lose an additional amount of energy:
The energy is used to warm the
melted ice to Tfinal:
Now we will combine all the
separate terms. Energy was removed from the water to first melt
the ice and then to warm the ice water to Tfinal. The toal energy
lost by the warm water is: