Heating Curve of Water
1. Fill a 250 ml beaker with ice and set it on a ring stand over an unlit Bunsen
burner.
2. Collect a TI-84 calculator and a CBL suitcase. (CBL stands for Calculator Based
Laboratory)
3. Connect the top of the calculator to the bottom of the CBL with a black link.
4. Connect the temperature probe to Channel 1 on the top of the CBL. The
temperature probe looks like a flat gray ribbon with a white wire on the end.
5. Run the probe down the ring stand so that the white part of the probe is in the
beaker of ice and no part of the probe is likely to touch the Bunsen burner flame.
6. Turn on both instruments. Check that the CBL says on the screen “ C” and the
temperature reading that it is giving is somewhere around 20 degrees. If not
press the mode button on the CBL until it does.
7. On the calculator, press the purple button labeled “APPS”
8. Arrow down until you find the program labeled “ChemBio”
9. Press Enter twice
10. Choose “Set Up Probes” and press enter
11. Type “1” and press enter
12. Choose “Temperature” and press enter
13. Type “1” and press enter
14. Choose “Collect Data” and press enter
15. Choose “Time Graph” and press enter
16. Type “10” and press enter. This will cause the calculator to read the temperature
of your system every 10 seconds.
17. Type “90” and press enter. This will cause the calculator to collect 90 data points,
which will be 15 minutes.
18. Press Enter
19. If you did not make a mistake, choose “Use time setup” and press enter. If you
made a mistake and want to change, choose “Modify setup.”
20. Type “0” and press enter. This will cause the graph you are creating to have a
minimum y value of 0. This is the normal freezing point of water.
21. Type “105” and press enter. This will cause the graph to have a maximum y
value of 105, which is a bit above the normal boiling point of water.
22. Type “10” and press enter. This will cause the graph to have a tick mark on the y
axis every 10 degrees.
23. When it looks like everything is good, light the Bunsen burner and press enter. If
all goes well, a set of axes will appear and a graph will begin to grow.
24. When you reach the boiling point and the temperature has remained stable for a
while, call your instructor to help you add some salt to the boiling water. Don’t
do this by yourself, because it can get a little bit exciting.
25. When the graph is done, you will get a message telling you that the calculator
stored the time data in L1 and the temperature data in L2. Press enter.
26. You should see a copy of your graph.
27. Connect the calculator to the computer using the black link, choose get graph and
print copies of the graph for all members of your group. Paste the graph into your
lab book.
Questions:
1. What is the boiling point of water?
2. Why is the boiling point lower than 100 C
3. Did you expect the water to continue getting hotter and hotter indefinitely?
4. What happened to the temperature immediately after the salt was added?
5. What happened to the boiling point of water after salt has been added?
6. What is the mathematical term for the shape of your graph?