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Chemistry
Sensors:
Loggers:
Temperature
Any EASYSENSE
Logging time: EasyLog
24 Heat of fusion of ice
Read
When a substance changes state e.g. from liquid to solid, the temperature of the substance does not
change as more energy is added. When pure solid water (ice) at 0oC, changes to liquid water at 0oC,
there is no change in temperature. At the point of a change in state any energy that is added (or
removed) is used in the state change instead of raising (or lowering) the temperature.
In this experiment you will measure the temperature change of a beaker of water as the ice in the
beaker melts. To calculate the heat that flows from the water into the ice, you can use the
relationship:
q = Cp•m•ΔΤ
Where q stands for heat flow, Cp is the specific heat capacity of water, m is mass (in grams) of the
water used, and ΔΤ is the change in temperature. For water, Cp is 4.18 J/g oC.
To data logger
Temperature
Sensor
Expanded
polystyrene
cup
Beaker
L3 Chemistry
24 - 1(V2)
What you need
1.
An EASYSENSE logger.
2. A Smart Q Temperature Sensor.
3. Expanded polystyrene cup or insulated beaker.
4. Beaker to support the cup.
5. Retort stand, boss, and clamp.
6. Measuring cylinder (100 cm3).
7. Measuring cylinder (150 cm3).
8. Supply of warm water (approx 60 – 70oC).
9. Ice cubes.
10. Drying cloth.
What you need to do
You need to be accurate in measurements and record the actual values used, for example if you used
101 cm3 of water make a note of this.
1.
Set up the apparatus as shown. Make sure the tip of the Temperature sensor does not touch
any of the sides of the cup. Leave enough space at the top of the cup to be able to add ice and
remove unwanted ice later in the experiment.
2. Connect the Temperature sensor to an input of the logger.
3. Pour 100 cm3 of water, at about 60oC, into the cup. The volume used will be V1.
4. From the EasySense software’s Home screen select EasyLog.
5. Click on Start to begin logging.
6. Wait until the temperature reaches a maximum (it will take a few seconds for the sensor to
reach the temperature of the warm water). This maximum will determine the initial
temperature, T1, of the water. Record this temperature in the results table (or you can find
this data after the experiment has finished from the logged temperature changes).
7. As soon as this maximum temperature is reached, fill the polystyrene cup with “dry” ice cubes
(i.e. the ice should not have water dripping off it, if necessary pat the cubes dry with a paper
towel.).
8. Use a stirring rod to stir the mixture as the temperature falls towards 0oC. As the ice melts
add more ice cubes to keep the temperature falling.
9. When the temperature falls to about 4oC, quickly remove any unmelted ice (using tongs or a
spoon).
10. Continue stirring until the temperature reaches a minimum (and begins to rise again). This
minimum temperature is T2.
11. When the temperature being recorded shows a definite rise click on Stop to finish logging.
12. Remove the sensor from the water and pour the water into a 150 cm3 measuring cylinder to
find the end volume. Record this as V2.
L3 Chemistry
24 - 2(V2)
Results and analysis
Item
Value
Initial water temperature, T1 (oC)
o
C
Final water temperature, T2 (oC)
o
C
Change in water temperature, ΔΤ (oC)
1.
2.
3.
4.
C
Final water volume, V2, (cm3)
cm3
Initial water volume, V1, (cm3)
cm3
Volume of melt, (cm3)
cm3
Subtract T2 – T1 to determine ΔΤ, the change in water temperature.
Calculate the volume of ice that was melted (V2 –V1).
Find the mass of ice melted (use 1.0 g/cm3 as the density of water).
Calculate the energy (in joules) released by the 100 g of liquid water as it cooled
(q = Cp•m•ΔT).
5. Now calculate the heat of fusion, the energy required to melt one gram of ice (in J/g H2O).
6. Use your answer to Step 5 and the molar mass of water to calculate the molar heat of fusion
for ice (in kJ/mol H2O).
Calculations table
Change in water temperature, ΔΤ (oC)
Volume of ice melt, (cm3)
C
cm3
Mass of ice melted
g
Heat released by cooling water (q = Cp•m•ΔΤ)
J
J/g ice melted (heat of fusion)
J/g
kJ/mol ice melted (molar heat of fusion)
Percent difference
1.
o
kJ/mol
%
What were the sources of error in the experiment?
2. How could you control the potential for error?
L3 Chemistry
24 - 3(V2)