4 Heat of Fusion for Ice Computer

4 Heat of Fusion for Ice Computer
Computer
Heat of Fusion for Ice
4
Melting and freezing behavior are among the characteristic properties that give a pure substance
its unique identity. As energy is added, pure solid water (ice) at 0°C changes to liquid water
at 0°C.
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In this experiment, you will determine the energy (in joules) required to melt one gram of ice.
You will then determine the molar heat of fusion for ice (in kJ/mol). Excess ice will be added to
warm water, at a known temperature, in a Styrofoam cup. The warm water will be cooled down
to a temperature near 0°C by the ice. The energy required to melt the ice is removed from the
warm water as it cools.
To calculate the heat that flows from the water, you can use the relationship
co
q = Cp•m•t
where q stands for heat flow, Cp is specific heat, m is mass in grams, and t is the change in
temperature. For water, Cp is 4.18 J/g°C.
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OBJECTIVES
In this experiment, you will
MATERIALS
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 Determine the energy (in Joules) required to melt one gram of ice.
 Determine the molar heat of fusion for ice (in kJ/mol).
Styrofoam cup
ring stand
utility clamp
ice cubes
stirring rod
warm water
al
ua
computer
Vernier computer interface
Logger Pro
Temperature Probe
250 mL beaker
100 mL graduated cylinder
tongs
Ev
PROCEDURE
1. Connect the probe to the computer interface. Prepare the computer for data collection by
opening the file “04 Heat of Fusion” from the Chemistry with Vernier folder.
2. Place a Styrofoam cup into a 250 mL beaker as shown in Figure 1.
3. Use a utility clamp to suspend the Temperature Probe on a ring stand as shown in Figure 1.
4. Use a 100 mL graduated cylinder to obtain 100.0 mL of water at about 60°C from your
instructor. Record this as V1.
5. Obtain 7 or 8 large ice cubes.
6. Lower the Temperature Probe into the warm water (to about 1 cm from the bottom).
Chemistry with Vernier
4-1
Computer 4
7. Click
to begin data collection. Wait until the temperature reaches a maximum (it will
take a few seconds for the cold probe to reach the temperature of the warm water). This
maximum will determine the initial temperature, t1, of the water. As soon as this maximum
temperature is reached, fill the Styrofoam cup with ice cubes. Shake excess water from the
ice cubes before adding them (or dry with a paper towel). Record the maximum temperature,
t1, in your data table.
Figure 1
8. Use a stirring rod to stir the mixture as the temperature approaches 0°C. Important: As the
ice melts, add more large ice cubes to keep the mixture full of ice!
9. When the temperature reaches about 4°C, quickly remove the unmelted ice (using tongs).
Continue stirring until the temperature reaches a minimum (and begins to rise). This
minimum temperature is the final temperature, t2, of the water. Record t2 in your data table.
Click
when you have finished collecting data.
10. Use the 100 mL graduated cylinder to measure the volume of water remaining in the
Styrofoam cup to the nearest 0.1 mL. Record this as V2.
11. You can confirm your data by clicking the Statistics button, . The minimum
temperature (t2) and maximum temperature (t1) are listed in the floating box on the graph.
PROCESSING THE DATA
1. Use the equation t = t2 – t1 to determine t, the change in water temperature.
2. Subtract to determine the volume of ice that was melted (V2 –V1).
3. Find the mass of ice melted using the volume of melt (use 1.00 g/mL as the density of water).
4. Use the equation given in the introduction of this experiment to calculate the energy (in
joules) released by the 100 g of liquid water as it cooled through t.
5. Now use the results obtained above to determine the heat of fusion—the energy required to
melt one gram of ice (in J/g H2O).
4-2
Chemistry with Vernier
Heat of Fusion for Ice
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).
7. Find the percent error for the molar heat of fusion value in Step 6. The accepted value for
molar heat of fusion is 6.01 kJ/mol.
DATA AND CALCULATIONS
Initial water temperature, t1
°C
Final water temperature, t2
°C
Change in water temperature, t
°C
Final water volume, V2
mL
Initial water volume, V1
mL
Volume of melt
mL
Mass of ice melted
g
Heat released by cooling water (q = Cp•m•t)
J
J/g ice melted (heat of fusion)
J/g
kJ/mol ice melted (molar heat of fusion)
kJ/mol
Percent error
%
Chemistry with Vernier
4-3
Vernier Lab Safety Instructions Disclaimer
THIS IS AN EVALUATION COPY OF THE VERNIER STUDENT LAB.
This copy does not include:

Safety information

Essential instructor background information

Directions for preparing solutions

Important tips for successfully doing these labs
The complete Chemistry with Vernier lab manual includes 36 labs and essential teacher
information. The full lab book is available for purchase at http://www.vernier.com/cwv
Vernier Software & Technology
13979 S.W. Millikan Way • Beaverton, OR 97005-2886
Toll Free (888) 837-6437 • (503) 277-2299 • FAX (503) 277-2440
[email protected] • www.vernier.com
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