WS F: Phase Change Problems Worksheet
Name____________________
1.
2.
In the diagram above, label all of the states of matter.
Assuming the above diagram is water, label the temperatures of the flat portions
of the diagram above.
3. In the first rising portion of the graph (a), describe what is happening as energy is
added. Discuss this in terms of the kinetic molecular theory.
4. In the 1st flat portion of the graph (b), describe what is happening as energy is
added. Discuss this in terms of bonding forces of attraction.
5. In the 2nd rising portion of the graph (c), describe what is happening as energy is
added. Discuss this in terms of the kinetic molecular theory.
6. In the 2nd flat portion of the graph (d), describe what is happening as energy is
added. Discuss this in terms of bonding forces of attraction.
7. In the 3rd rising portion of the graph (e), describe what is happening as energy is
added. Discuss this in terms of the kinetic molecular theory
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m.p.
(ºC)
0.00
∆Hfus
(kJ/g)
0.333
b.p.
ºC
100.00
∆Hvap
(kJ/g)
2.26
Grain
Alcohol
-98
0.0987
64
1.10
Benzene
5.0
0.1265
80
0.394
Substance
H2O
Specific Heat –C(J/g ºC)
Ice: 2.09
Water: 4.18
Steam: 1.7
Solid: 1.2
Liquid: 2.4
Gas: 1.9
Solid: 0.55
Liquid: 0.96
Gas: 1.09
8. What is the formula used for calculating the heat involved in a phase change?
9. During a phase change, how much does the temperature change? How much does
the KE change? Does the potential energy change?
10. What is the formula used to calculate the heat required to warm or cool one phase
of matter?
11. When you heat one phase of matter, how do you know that the KE changes?
12. What is meant by the negative sign in an answer like "-46.8 kJ"? When would
you use a positive sign?
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13. If you must add 25 kJ to raise the temperature of an ice cube from -15°C to -10°C,
is this an endothermic or an exothermic process.
14. How much heat is required to raise 40 grams of water from 30°C to 70°C?
15. How much water can be raised from 25°C (room temperature) to 37°C body
temperature by adding the 2,000 kJ in a Snickers Bar?
16. Which releases more heat when it is lowered by 8°C, 100 grams of ice, water, or
steam? How much heat is released by the one which releases the most?
Water will release the most energy since the specific heat of liquid water is the
highest
17. How much heat does it take to melt 65 grams of ice at 0°C?
18. Calculate the amount of energy required to change 100 grams of solid ice at 0°C
to gaseous steam at 100°C. (Be aware of units: kJ or J?) How many steps does
this take?
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19. Calculate the amount of energy released by cooling 59 grams of liquid water from
+25°C to ice at -25°C. (Be aware of units: kJ or J?) How many steps does this
take?
20. How much heat would it take to raise 5 grams of H2O from -50°C to +200°C?
How many steps does this take?
21. How much heat is needed to melt a tray of 14 ice cubes, presently at 0˚ C, each
having a mass of 35 g.
22. How much energy is required to bring 45 g of benzene from - 10˚C to 70˚C?
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23. How much energy is required to bring 1 kg of grain alcohol in the liquid state
from its freezing point to 10˚ above its boiling point?
24. What will be the temperature of water if 2000 J or energy is added to 100 g of ice
at 0˚C? Will all of it melt? If not how much has melted and how much remains?
25. What will be the temperature of grain alcohol if 10,000 J of energy is added to
400 g of grain alcohol at -50˚C?
26. What will be the temperature of benzene if 30,000 J of energy is added to 1 kg of
benzene at -5˚C?
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WS F: Phase Change Problems Worksheet
Name____________________
1.
2.
In the diagram above, label all of the states of matter.
Assuming the above diagram is water, label the temperatures of the flat
portions of the diagram above.
3. In the first rising portion of the graph (a), describe what is happening as
energy is added. Discuss this in terms of the kinetic molecular theory.
4. In the 1st flat portion of the graph (b), describe what is happening as energy is
added. Discuss this in terms of bonding forces of attraction.
5. In the 2nd rising portion of the graph (c), describe what is happening as energy
is added. Discuss this in terms of the kinetic molecular theory.
6. In the 2nd flat portion of the graph (d), describe what is happening as energy
is added. Discuss this in terms of bonding forces of attraction.
7. In the 3rd rising portion of the graph (e), describe what is happening as
energy is added. Discuss this in terms of the kinetic molecular theory
-6-
m.p.
(ºC)
0.00
∆Hfus
(kJ/g)
0.333
b.p.
ºC
100.00
∆Hvap
(kJ/g)
2.26
Grain
Alcohol
-98
0.0987
64
1.10
Benzene
5.0
0.1265
80
0.394
Substance
H2O
Specific Heat –C(J/g ºC)
Ice: 2.09
Water: 4.18
Steam: 1.7
Solid: 1.2
Liquid: 2.4
Gas: 1.9
Solid: 0.55
Liquid: 0.96
Gas: 1.09
8. What is the formula used for calculating the heat involved in a phase change?
Q=∆Hm
9. During a phase change, how much does the temperature change? How much
does the KE change? Does the potential energy change?
None: None: PE changes
10. What is the formula used to calculate the heat required to warm or cool one
phase of matter?
Q=mc∆T
11. When you heat one phase of matter, how do you know that the KE changes?
Because the Temperature changes
12. What is meant by the negative sign in an answer like "-46.8 kJ"? When would
you use a positive sign?
Energy is released
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13. If you must add 25 kJ to raise the temperature of an ice cube from -15°C to 10°C, is this an endothermic or an exothermic process.
Endothermic: You are adding the energy
14. How much heat is required to raise 40 grams of water from 30°C to 70°C?
Q  mcT
 (40 g )( 4.18 g JC )( 40C )  6688 J  6.7kJ
15. How much water can be raised from 25°C (room temperature) to 37°C body
temperature by adding the 2,000 kJ in a Snickers Bar?
Q  mcT
2000kJ  2,000,000 J
2,000,000 J  m(4.18 g JC )(12C )
m  39872 g  39.8kg
16. Which releases more heat when it is lowered by 8°C, 100 grams of ice, water,
or steam? How much heat is released by the one which releases the most?
Water will release the most energy since the specific heat of liquid water is the
highest
Q  mcT
(100 g )( 4.18 g JC )(8C )  3344 J  3.3kJ
17. How much heat does it take to melt 65 grams of ice at 0°C?
Q  H fusm
 (0.333 kJg )(65g )  21.6kJ
18. Calculate the amount of energy required to change 100 grams of solid ice at
0°C to gaseous steam at 100°C. (Be aware of units: kJ or J?) How many
steps does this take?
0 ( s )  0 (l ) : Q  H fus m  (0.333 kJg )(100 g )  33.3kJ
0 (l )  100 (l ) : Q  mcT  (100 g )( 4.18 g JC )(100C )  41800 J  41.8kJ
100 (l )  100 ( g ) : Q  H vap m  (2.26 g JC )(100 g )  226kJ
226kJ  41.8kJ  33.3kJ  301.1kJ
-8-
19. Calculate the amount of energy released by cooling 59 grams of liquid water
from +25°C to ice at -25°C. (Be aware of units: kJ or J?) How many steps
does this take?
25(l )  0(l ) : Q  mcT  (59 g )( 4.18 g JC )( 25C )  6166 J  6.2kJ
0(l )  0( s ) : Q  H fus m  (0.333 g JC )(59 g )  19.6kJ
0( s )  25C( s ) : Q  mcT  (59 g )( 2.09 g JC )( 25C )  3082 J  3.1kJ
6.2kJ  19.6kJ  3.1kJ  28.9kJ
20. How much heat would it take to raise 5 grams of H2O from -50°C to +200°C?
How many steps does this take?
 50( s )  0(l ) : Q  mcT  (5 g )( 2.09 g JC )(50C )  522 J  0.52kJ
0( s )  0(l ) : Q  H fus m  (0.333 kJg )(5 g )  1.67kJ
0(l )  100(l ) : Q  mcT  (5 g )( 4.18 g JC )(100C )  2090 J  2.09kJ
100(l )  100( g ) : Q  H vap m  (2.26 g JC )(5 g )  11.3kJ
100( g )  200( g ) : Q  mcT  (5 g )(1.7 g JC )(100C )  850 J  0.85kJ
0.52kJ  1.67kJ  2.09kJ  11.3kJ  0.85kJ  16.43kJ
21. How much heat is needed to melt a tray of 14 ice cubes, presently at 0˚ C,
each having a mass of 35 g.
35 g
14iceCube
x
 490 gIce
iceCube
1
Q  H fus m  (0.333 kJg )( 490 g )  163kJ
22. How much energy is required to bring 45 g of benzene from - 10˚C to 70˚C?
 10( s )  5( s ) : Q  mcT  (45 g )(0.55 g JC )(15C )  371J  0.37kJ
5( s )  5(l ) : Q  H fus m  (0.1265 g JC )( 45 g )  5.69kJ
5(l )  70C(l ) : Q  mcT  (45 g )(0.96 g JC )(65C )  2808 J  2.81kJ
0.37kJ  5.69kJ  2.81kJ  8.87kJ
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23. How much energy is required to bring 1 kg of grain alcohol in the liquid state
from its freezing point to 10˚ above its boiling point?
 98 (l )  64 (l ) : Q  mcT  (1000 g )( 2.4 g JC )(162C )  388800 J  389kJ
64 ( l )  64 ( g ) : Q  H vap m  (1.10 g JC )(1000 g )  1100kJ
64 ( g )  74C ( g ) : Q  mcT  (1000 g )(1.90 g JC )(10C )  19,000 J  19.0kJ
389kJ  1100kJ  19.0  1508kJ
24. What will be the temperature of water if 2000 J or energy is added to 100 g of
ice at 0˚C? Will all of it melt? If not how much has melted and how much
remains?
0 ( s )  0 (l ) : Q  H fus m  (0.333 kJg )(100 g )  33.3kJ  2kJ
Q  H fus m
2kJ  (0.333 kJg )m
6.0 grams
6% willmelt
Temp..will ..be...0C..It ..won' t..all ..melt
25. What will be the temperature of grain alcohol if 10,000 J of energy is added to
400 g of grain alcohol at -50˚C?
 50 ( s )  64 (l ) : Q  mcT  (400 g )( 2.4 g JC )(114C )  109440 J  10,000 J
Q  mcT
10,000 J  (400 g )( 2.4 g JC )( T )
T  10.4C
 50C  10C  40C
26. What will be the temperature of benzene if 30,000 J of energy is added to 1 kg
of benzene at -5˚C?
 5 ( s )  5 ( s ) : Q  mcT  (1000 g )(0.55 g JC )(10C )  5500 J
StillMoreE nergyLeft
Q  H fus m  (0.1265 kJg )(1000 g )  126.5kJ  126500 J
Since : It : Won' t : All : Melt :: Then : It : will : be : at : it ' s : freezing : po int
 5
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