Temperature, Heat, & Phase Change - Graphing Freezing and Melting
of Water
ABSTRACT Follow ETO guide questions.
INTRODUCTION
Background
Freezing point is the temperature at which a substance turns from liquid to solid. Melting
point is the temperature at which a substance turns from solid to liquid. Freezing point
and melting point are intensive physical properties of a pure substance. In this
experiment, you will determine and compare the freezing and melting points of water.
You will also observe the relationships between heat, temperature, and phase change.
Problem: Can the temperature of water change during a phase change?
Identify the independent and dependent variables:
Independent variable:
Dependent variable:
Hypothesis:
MATERIALS
Pasco Sparks Data System
Temperature Probe
Distilled and tap water
Ring stand
Utility clamp
Spatula or spoon
test tube
400 mL beaker
10 mL graduated cylinder
salt (NaCl)
stirring rod
ice
Setup:
1
PROCEDURE
PART I – Freezing
1. Put about 50 mL of water and 5 to 6 ice cubes into a 400 mL beaker.
2. Put 5 mL of distilled water into a test tube and use a utility clamp to fasten the test
tube to a ring stand. The test tube should be situated above the water bath. Place
a temperature probe into the water inside the test tube. Make sure the probe
remains submerged throughout the experiment.
3. Plug in the AC power cord. Turn on the Sparks system. Plug the white
temperature probe into the left-hand opening on top of the Sparks system.
4. On the “Home” screen, press BUILD.
5. On the left-hand menu, press TEMPERATURE first, and then press TIME.
6. On the right side, press the graph icon.
7. On the bottom right, press OK.
8. On the bottom of the new screen, press the tab with the circle icon.
9. Select sampling mode, PERIODIC.
10. Select sampling rate unit, SECONDS.
11. Select sampling rate, 30.
12. Press OK.
13. At the top, touch the page icon.
14. On the left-hand menu, press TEMPERATURE first, and then press TIME.
15. Select the table icon.
16. On the bottom right, press OK.
17. You may switch between the table and the graph using the left arrow icon at the
top left, next to the home icon.
18. When everything is set up in the procedure begin data collection:
 Press the green right arrow on the bottom left to begin data collection.
Note: It will take 30 seconds for the graph to appear with the first data
point plotted.
 When the graph appears on the calculator screen, lower the test tube into
the ice-water bath.
19. Soon after lowering the test tube, add 5 spoons for salt to the beaker and stir with
a stirring rod. Continue to stir the ice-water bath during Part I. Make sure your
probe remains submerged throughout the rest of the lab!!
20. Slightly, but continuously, move the probe during the first 8 minutes of Part I. Be
careful to keep the probe in and not above, the ice as it forms. When 10 minutes
have gone by, stop moving the probe and allow it to freeze in the ice. Add more
ice cubes and a little more salt to the beaker as the original ice cubes get smaller.
Frost should appear on the outside of the beaker if you are getting it cold enough.
21. When 15 minutes have passed, push the red right arrow on the bottom left again
to stop the data collection. IMPORTANT: Keep the test tube submerged in the
ice water bath until step 25.
22. At the top, touch the page icon. You can scroll through the data using the touch
screen.
23. Record the temperature values in your data table similar to the one shown
below in the Results (to be hand graphed later by hand).
PART II - Melting
24. Press HOME. When the warning comes up, choose NO, but beware you will
lose your data so make sure you copied it first!!!!
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25. Repeat steps 4 – 18 above, with the exception of “lowering the test tube into the
ice”, since it’s already there. Instead, after you begin the data collection again
and wait 30 seconds, raise the test tube up out of the ice water bath and leave
it melting in the air for 10-12 minutes.
26. Dispose of the ice water by pouring down the drain and rinse the beaker. Obtain
250 mL of warm tap water in the same 400 mL beaker. When 10 minutes have
passed, lower the test tube and its contents into this warm water bath.
27. When the time runs out, repeat step 22 and 23 above.
28. Clean-up.
DATA
PART I – Freezing
Time
(s)
30
60
90
120
150
180
210
240
Temp.
(oC)
Time
(s)
270
300
330
360
390
420
450
480
Temp.
(oC)
Time
(s)
510
540
570
600
630
660
690
Temp.
(oC)
Time
(s)
720
750
780
810
840
870
900
Temp.
(oC)
Time
(s)
270
300
330
360
390
420
450
480
Temp.
(oC)
Time
(s)
510
540
570
600
630
660
690
Temp.
(oC)
Time
(s)
720
750
780
810
840
870
900
Temp.
(oC)
PART II – Melting
Time
(s)
30
60
90
120
150
180
210
240
Temp.
(oC)
CONCLUSIONS
1. Graph your data in your lab book. According to your data and graph, what are
the freezing and melting points of water? If they are not exactly 0 0C, explain
possible reasons for the variation.
2. What happened to the water temperature during freezing? During melting? Give
a particle level explanation, using kinetic molecular theory, for what you
observed.
3. Was your hypothesis supported? Explain.
4. Phenyl salicylate, a compound closely related to the one found in aspirin, has a
freezing temperature of 41.5 oC. Sketch and label freezing and melting curves for
phenyl salicylate. Be sure to indicate the freezing temperature on the y-axis of
your graph.
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