Name:______________________________Class:__________________ Date:__________________
Assessment
Heat
Teacher Notes and Answers
9 Heat
CHANGES IN TEMPERATURE AND PHASE
1.
2.
3.
4.
Solution
Qw = Q m
cp,wmwTw = cpmm mTm
cp,wmw(Tf Tw) =
cp,m mm(Tf Tm )=
cp,mmm(Tm Tf )
b
c
a
d
Given
Q = 3.6 103 J
m = 0.25 kg
cp = 360 J/kg•°C
Solution
T =
c p ,m =
c pm
=
mm (Tm T f )
c p,m =
3
Q
c p , w m w (T f Tw )
3.610 J
( 4186J/kg • °C)(0.150kg )(29.0°C25.0°C)
(360 J/kg • °C)(0.25 kg )
(7.5010 2 kg )(93.0°C29.0°C)
1
c p ,m =
= 4.010 °C
( 4186J/kg • °C)(0.150kg )(4.0°C)
5.
6.
7.
8.
9.
a
c
b
a
Water has a much larger specific heat
capacity than does air. Therefore, for a given
amount of energy provided to both by
sunlight, the temperature of each kilogram
of air rises more than does the temperature
of a kilogram of water. Over time, the air
reaches a high temperature and becomes hot
while the water’s temperature has not
increased that much, and therefore still
remains cool.
10. 5.2 102 J/kg•°C
Given
Tm = 93.0°C
Tw = 25.0°C
Tf = 29.0°C
mm = 7.50 102 kg
mw = 0.150 kg
cp,w = 4186 J/kg•°C
(7.5010 2 kg )(64.0°C)
=
5.2 10 2 J/kg • °C
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
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Section Quizzes
Name:______________________________Class:__________________ Date:__________________
Assessment
Heat
Section Quiz: Changes in Temperature and Phase
Write the letter of the correct answer in the space provided.
_____ 1. What is the quantity of energy needed to raise the temperature of a unit
mass of a substance by 1°C called?
a. latent heat
b. specific heat capacity
c. internal energy
d. thermal energy
_____ 2. Which property of a substance is not needed to determine the amount
of energy transferred as heat to or from the substance?
a. temperature change
b. specific heat capacity
c. volume
d. mass
_____ 3. The specific heat capacity of a substance is determined using a
calorimeter containing water. Besides the substance’s mass and the
change in temperature of the test substance, what other quantities must
be measured in calorimetry?
a. the mass, specific heat capacity, and temperature change of the
water
b. the volume, specific heat capacity, and temperature change of the
water
c. the density, specific heat capacity, and temperature change of the
water
d. the mass, thermal conductivity, and temperature change of the water
_____ 4. A metal bolt in a calorimeter gives up 3.6 103 J of energy as heat to
the surrounding water. The bolt has a mass of 0.25 kg and a specific
heat capacity of 360 J/kg•°C. What is the change in the bolt’s
temperature?
a. 0.40°C
b. 2.5°C
c. 4.0°C
d. 4.0 101 °C
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
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Section Quizzes
Name:______________________________Class:__________________ Date:__________________
Heat continued
_____ 5. What is the energy transferred to or from a unit mass of a substance
during a phase change called?
a. latent heat
b. specific heat capacity
c. internal energy
d. thermal energy
_____ 6. During a phase change, which of the following properties does not
change?
a. internal energy
b. physical state
c. temperature
d. volume
_____ 7. In a heating curve, what does a line with a positive slope indicate?
a. the change in the substance’s state with added or removed energy
b. the increase in the substance’s temperature with added energy
c. the decrease in the substance’s temperature with added energy
d. the change in the substance’s latent heat with added energy
_____ 8. In a heating curve, what does a line with zero slope indicate?
a. the change in the substance’s state with added or removed energy
b. the increase in the substance’s temperature with added energy
c. the decrease in the substance’s temperature with added energy
d. the change in the substance’s specific heat capacity with added
energy
9. Using the concept of specific heat capacity, explain why water remains cool
on a hot day whereas the air above it becomes hot.
_________________________________________________________________
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10. A metal part with a mass of 7.50 102 kg and a temperature of 93.0°C is
placed in a calorimeter containing 0.150 kg of water. If the initial temperature
of the water is 25.0°C, and the final temperature of the part and water 29.0°C,
what is the specific heat capacity of the part? (cp,w = 4186 J/kg•°C)
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
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Section Quizzes