Name:______________________________Class:__________________ Date:__________________
Assessment
Heat
Teacher Notes and Answers
9 Heat
DEFINING HEAT
1.
2.
3.
4.
5.
c
b
a
c
d
Given
TC = 37°C
Tw = 15°C
Solution
T = 37°C 15°C = 22°C =
29°C 7°C
6. c
7. b
8. c
Given
U = 18 J
Solution
PE = 0 J; KEf = 0 J;
10. 401 m
Given
U = 1770 J
m = 0.450 kg
g = 9.81 m/s2
Solution
PE + KE + U = 0
The kinetic energy increases with the
decrease in potential energy, and then
decreases with the increase in the internal
energy of the water. Thus, the net change in
kinetic energy is zero. Assuming final
potential energy has a value of zero, the
change in the internal energy equals:
0 PEi + U = 0
U = PEi = mgh
h=
PE + KE + U = 0 = KEi + U
KEi = U = 18 J
9. Energy is transferred as heat from the
particles with higher kinetic energies, and
thus higher temperature, to particles with
lower kinetic energies, and lower
temperature, through collisions. In most
cases, energy is given up from the particles
with higher energies to those with lower
energies. Overall, this causes the
temperature of the object originally at higher
temperature to decrease, and the temperature
of the originally lower temperature object to
increase. When the average kinetic energies
of particles in both objects are the same, the
amount of energy transferred from the first
object to the second is the same as the
energy transferred from the second object to
the first. At this point, no net energy is
exchanged, and the objects have the same
temperatures. They are then in thermal
equilibrium.
U
mg
=
1770 J
(0.450 kg)(9.81 m/s2 )
=
401 m
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Physics
1
Section Quizzes
Name:______________________________Class:__________________ Date:__________________
Assessment
Heat
Section Quiz: Defining Heat
Write the letter of the correct answer in the space provided.
_____ 1. What term is defined as the energy transferred between objects with
different temperatures?
a. internal energy
b. work
c. heat
d. thermal equilibrium
_____ 2. What must be true if energy is to be transferred as heat between two
bodies in physical contact?
a. The two bodies must have different volumes.
b. The two bodies must be at different temperatures.
c. The two bodies must have different masses.
d. The two bodies must be in thermal equilibrium.
_____ 3. What occurs to the particles in a substance at low temperature when
energy is transferred to the substance as heat?
a. The average kinetic energy of the particles increases.
b. The average kinetic energy of the particles remains constant.
c. The average kinetic energy of the particles decreases.
d. The average kinetic energy of the particles varies unpredictably.
_____ 4. If energy is transferred spontaneously as heat from a substance with a
temperature of T1 to a substance with a temperature of T2, which of the
following statements must be true?
a. T1 < T2
b. T1 = T2
c. T1 > T2
d. More information is needed.
_____ 5. A container with a temperature of 37°C is submerged in a bucket of
water with a temperature of 15°C. An identical container with a
temperature of T1 is submerged in an identical bucket of water with a
temperature of T2. If the amounts of energy transferred as heat between
the containers and the water are the same in both cases, which of the
following statements is true?
a. T1 = 5°C; T2 = 37°C
b. T1 = 10°C; T2 = 47°C
c. T1 = 12°C; T2 = 32°C
d. T1 = 7°C; T2 = 29°C
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Physics
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Section Quizzes
Name:______________________________Class:__________________ Date:__________________
Heat continued
_____ 6. What is the process by which energy is transferred by the motion of
cold and hot matter?
a. thermal conduction
b. thermal insulation
c. convection
d. radiation
_____ 7. Which of the following is not a good thermal insulator?
a. ceramic
b. iron
c. fiberglass
d. cork
_____ 8. An arrow strikes a target, causing an internal energy increase of 18 J. If
the arrow is fired so that it enters the target at the same height above
the ground as when it was fired, what is the arrow's initial kinetic
energy?
a. 0 J
b. 9 J
c. 18 J
d. 27 J
9. Describe how energy is transferred between two objects at different
temperatures, and how they reach thermal equilibrium.
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10. A stone with a mass of 0.450 kg is dropped from the edge of a cliff. When the
stone strikes the ground, the internal energy of the stone and ground increase
by 1770 J. If the stone is initially at rest when it is dropped, how high above
the ground is the cliff? (g = 9.81 m/s2)
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Physics
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Section Quizzes