Heat and Temperature: Changes of phase
End of Module Questions
Useful data (that you don’t need to memorize):
Specific heat of liquid water: 1.00 cal/(g C) (you should know this one)
Specific heat of ice (solid water): 0.50 cal/(g C)
Heat of vaporization of water: 540 cal/g
Heat of fusion of water: 80 cal/g
1. If you start with 80 g of liquid water at 100 C and add 13,500 calories of heat, what will you
wind up with? (What will you have and what will the temperature be?)
2. If you start with 80 g of liquid water at 0 C and remove 1200 calories of heat, what will you
wind up with? (What will you have and what will the temperature be?)
3. If you start with 1.0 grams of liquid water at 40 C and add 600 calories of heat, what will you
have? Take this one in steps…
a. As an aid to answering this one, how much heat is required to raise the temperature of
the water to 100 C?
b. After the temperature has been raised to 100 C, how much of the 600 calories is left?
c. What will this remaining heat do?
d. After all 600 calories have been added, what will you have? What will the temperature
be?
4. If you start with 120 g of liquid water at 80 C and add 24,000 calories of heat, what will you
wind up with? Again, take this one in steps…
a. How much heat is required to raise the temperature of the water to 100 C?
b. After the temperature has been raised to 100 C, how much of the 24,000 calories is left?
c. What will this remaining heat do?
d. After all 24,000 calories have been added, what will you have? What will the
temperature be?
5. There are lots of steps to this one, but see if you can put them all together. If you start with 110
grams of solid ice at a temperature of -20 C and add 29,000 calories of heat, what will you
wind up with? (Hint: we count four different “steps” or four different things the heat has to do
along the way.)
6. If you start with 45 grams of liquid water at 10 C, how much heat must be removed to freeze it
solid?
More information that you don’t need to memorize:
Melting point of ethanol: -114 C
Boiling point of ethanol: 78 C
Specific heat of liquid ethanol: 0.58 cal/(g C)
Heat of vaporization of ethanol: 204 cal/g
Heat of fusion of ethanol: 25 cal/g
7. If you start with 25 grams of ethanol at 78 C and add 1,020 calories of heat, what will you wind
up with? (And what will the temperature be?)
8. If you start with 120 grams of ethanol at 48 C and add 24,000 calories of heat, what will you
wind up with and what will the temperature be?
9. Ethanol will still be a liquid when cooled by dry ice to a chilly -77 C. If you start with 50 grams
of liquid ethanol at a temperature of -77 C, how much heat would you need to remove to
freeze it solid?