Investigation 10: Mixing and Melting
PART A - MIXING WATER SAMPLES E QUILIBRIUM
Case 1: Mixing Equal amounts of hot water with cold water
1. Place 100 mL of cold water in a small foam cup. Measure its
temperature (Tcold) in Celsius and record in the data table.
2. Place 100 mL of hot water in a small foam cup. Measure its
temperature (Tcold) in Celsius and record in the data table. Be
careful, the hot water is HOT.
Glue this side down.
3. Before mixing the two samples together, check the prediction
you think best describes what will happen:
 The final temperature of the mixture will be the
temperature Tcold.
 The final temperature of the mixture will be closer to Tcold
than to Thot.
 The final temperature of the mixture will be approximately
halfway between Tcold and Thot.
 The final temperature of the mixture will be closer to Thot
than to Tcold.
 The final temperature of the mixture will be the
temperature Thot.
4. Now try to estimate the final temperature of the mixed water
samples: Estimated Tfinal = _____°C
5. Mix the hot and cold samples together, pouring them both
into the large foam cup. Gently stir the mixed samples with
your thermometer until you are sure the mixture is all at one
temperature. This is called the equilibrium temperature of
the water mixture. Record this in the data table.
CASE 1 DATA TABLE:
Temperature of 100 mL of cold water
(Tcold)
°C
Temperature of 100 mL of hot water (Thot)
°C
Equilibrium Temperature of the mixture
(Tfinal)
°C
6. Was your prediction correct? _________
Was your estimate close? _________
13. Before mixing the two samples together, check the prediction
you think best describes what will happen.
 The final temperature of the mixture will be closer to
Tcold than to Thot.
 The final temperature of the mixture will be
approximately halfway between Tcold and Thot.
 The final temperature of the mixture will be closer to
Thot than to Tcold.
14. Try to estimate the equilibrium temperature of the mixed
water samples, Tfinal =_____°C
7. Which water sample was the heat energy transferred FROM?
8. Which water sample was the heat energy transferred TO?
9. How do you know which sample the heat energy was
transferred TO and which sample the heat energy was
transferred FROM?
10. Why do you think the equilibrium temperature of the mixture
was close to halfway between their starting temperatures?
15. Mix the hot and cool samples together, pouring them both
into the large foam up. Gently stir and record the equilibrium
temperature.
CASE 2 DATA TABLE:
Temperature of 100 mL of cold water
(Tcold)
Temperature of 100 mL of hot water (Thot)
°C
Equilibrium Temperature of the mixture
(Tfinal)
°C
16. Was your prediction correct? _______
Was your estimate close? ________
17. Compare Case 2 with Case 1. Explain our results.
Case 2: Mixing hot water with twice as much cool water
11. Place 200 mL of cold water in a small foam cup. Measure its
temperature (Tcold) and record in the data table.
12. Place 100 mL of hot water in a small foam cup. Measure its
temperature (Tcold) and record in the data table.
°C
Investigation 10: Mixing and Melting
PART B – THE MELTING PROCESS
We will be adding hot water to ice. We want to find out if the hot
water has the same effect it has on the ice that it had on the cold
water. In Case2 of Part A, we adding 100 g of hot water to 200 g of
cold water. We will be replacing the 200 g of cold water with 200 g of
ice in this experiment so that we can compare it to Case 2.
18. Place 200 g of ice in the large foam cup. Make sure you have
only ice cubes, no liquid water. Find its temperature (Tice) in °C
and record here: (Tice) = ______°C
19. Place 100 mL of hot water in a small foam cup. Find its
temperature (Thot) and record here: (Thot) = ______°C
Glue this side down.
20. Can you predict how many milliliters of hot water will be
needed to completely melt the ice? (None of our experiments
thus far would help you make this prediction, so this is really
more of an educated guess.) Circle your best guess.
Less than 100mL
100mL
200mL
300mL
more than 300mL
21. Add the 100 mL of hot water to the ice. Stir gently until it
comes to equilibrium. Record the equilibrium temperature
when the temperature stops changing.
Equilibrium after adding 100mL hot water: (Tfinal) = ______°C
22. Did all of the ice melt? _____
23. If ice still remains in the mixture, add another 100mL of hot
water. Once again, stir the mixture gently and wait until the
mixture reaches thermal equilibrium.
Equilibrium after adding 200mL hot water: (Tfinal) = ______°C
24. Did all of the ice melt? _____
25. If ice still remains in the mixture, add another 100mL of hot
water. Once again, stir the mixture gently and wait until the
mixture reaches thermal equilibrium.
Equilibrium after adding 300mL hot water: (Tfinal) = ______°C
26. The ice and the cold water start at nearly the same
temperature. Did the first 100mL of hot water have the same
effect when added to the ice as it had when added to the cold
water? Explain your answer.
SUMMARY OF RESULTS
Part A, Case 2 – Adding hot water to liquid water at 0°C
When 100mL of hot water at ____°C was added to 200 mL of cold
(liquid) water at ____°C, the equilibrium temperature of the mixture
was Tfinal = ______°C
Part B – Adding hot water to solid water (ice) at 0°C
After 100 mL of hot water at ______°C was added to 200 grams/mL of
ice at ______°C, the equilibrium temperature of the mixture was
Tfinal = ______°C
After a second 100 mL of hot water at ______°C was added the
ice/water mixture, the equilibrium temperature of the mixture was
Tfinal = ______°C
After a third 100 mL of hot water at ______°C was added the
ice/water mixture, the equilibrium temperature of the mixture was
Tfinal = ______°C
27. Think about what is happening to the particles of water in the
ice as the ice melts. Are the particles themselves changing? Is
their kinetic energy changing? Is the way they are connected
to each other (bonded) changing? What would explain why it
takes so much hot water to melt the ice?