Preview Extract
Chapter 7 Heat Transfer and Change of Phase
7.1 Conduction
1) A substance absorbs heat energy by the process of
A) conduction.
B) convection.
C) radiation.
D) none of the above
Answer: D
2) Metals are both good heat and electrical conductors due to
A) similar thermal and electrical conductive properties.
B) looseness of outer electrons in metal atoms.
C) relatively high densities of metals.
D) high elasticity of metals.
E) ability of metals to transfer energy easily.
Answer: B
3) A good heat conductor is a
A) poor insulator.
B) good insulator.
C) neither
Answer: A
4) A poor conductor of heat is a
A) poor insulator.
B) good insulator.
C) neither
Answer: B
5) Your toes feel warmer on a rug than on a tile floor because the rug
A) is usually warmer than tile.
B) is a better insulator than tile.
C) has more thermal energy than tile.
D) all of the above
E) none of the above
Answer: B
6) If you were caught in freezing weather with only a candle for warmth, you would be warmer
in
A) an igloo.
B) a tent.
C) a wooden house.
Answer: A
7) One of the main reasons people can walk barefoot on red-hot coals of wood without burning
their feet has to do with
A) low temperature of the coals.
B) low thermal conductivity of the coals.
C) mind over matter techniques.
Answer: B
8) A good insulator
A) slows heat transfer.
B) prevents heat transfer.
C) quickens heat transfer.
Answer: A
9) A water-filled paper cup held in a flame will not catch fire because
A) the inside of the paper is wet.
B) water is an excellent conductor of heat.
C) paper is a good conductor of heat.
D) the paper cup cannot become appreciably hotter than the water it contains.
Answer: D
10) Write a short paragraph distinguishing between conduction and convection. Give two
examples of each.
Answer: Thermal conduction occurs when molecular bumping from warm to cool areas transfers
kinetic energy. Convection occurs when atoms or molecules travel in space. Whereas conduction
occurs primarily in solids, convection occurs in fluids–liquids or gases. When cold water is
poured into hot soup, the water soon spreads by convection to all parts of the mixture. When a
spoon is placed in the hot soup, the whole spoon becomes hot by conduction.
7.2 Convection
1) The process of convection occurs in
A) solids.
B) liquids.
C) gases.
D) fluids.
E) none of the above
Answer: D
2) Warm air rises because faster moving molecules tend to move to regions of less
A) density.
B) pressure.
C) both
Answer: C
3) Hot steam that issues from a pressure cooker expands and
A) increases in temperature.
B) can cause severe burns.
C) cools.
D) all of the above
E) none of the above
Answer: C
4) Convection currents in the air near a seashore are produced by
A) shifting winds.
B) unequal heating of land and water.
C) varying temperatures.
D) none of the above
Answer: B
5) Coastal winds shift from night to day due to
A) conduction.
B) convection.
C) radiation.
D) all about equally.
Answer: B
6) Blow on your hand with your open mouth and you feel the warmth of your breath. Pucker
your lips so your breath expands as you blow and your breath is
A) still warm.
B) cooler.
C) neither
Answer: B
7) If a volume of air is warmed, it expands. If a volume of air expands, it
A) warms.
B) cools.
C) neither
Answer: B
8) When a volume of air is compressed, its temperature
A) increases.
B) decreases.
C) neither
Answer: A
9) The gush of steam that issues from the escape valve of a pressure cooker is relatively cool
A) above the opening where expansion is prominent.
B) close to the opening.
C) none of the above
Answer: A
7.3 Radiation
1) Radiant energy emitted by our planet is
A) terrestrial energy.
B) the result of radioactivity in Earth's interior.
C) electromagnetic.
D) all of the above
Answer: D
2) The higher the frequency of a wave, the
A) shorter the wavelength.
B) longer the wavelength.
C) neither
Answer: A
3) The average frequency of radiant energy is directly proportional to the
A) Celsius temperature of the emitter.
B) Fahrenheit temperature of the emitter.
C) kelvin temperature of the emitter.
D) all of the above
E) none of the above
Answer: C
4) The higher the temperature of an object, the
A) higher frequency it radiates.
B) lower frequency it radiates.
C) none of the above
Answer: A
5) The higher the temperature of an object, the
A) longer the wavelengths it radiates.
B) shorter the wavelengths it radiates.
C) none of the above
Answer: B
6) A star that is twice as hot as another has twice the
A) Celsius temperature.
B) Fahrenheit temperature.
C) kelvin temperature.
D) any of the above
E) none of the above
Answer: B
7) Which emits the highest frequency of radiation?
A) a red-hot star
B) the Sun
C) a blue-hot star
D) all the same
Answer: B
8) If an object radiates more energy than it absorbs, its
A) thermal energy decreases.
B) temperature decreases.
C) both
D) neither
Answer: C
9) If an object radiates more energy than it reflects, its
A) thermal energy decreases.
B) temperature decreases.
C) both
D) neither
Answer: C
10) Objects that are good radiators generally
A) absorb radiation relatively well.
B) reflect radiation relatively well.
C) both
D) neither
Answer: A
11) Hot water will cool to room temperature faster in a
A) black pot.
B) silver pot.
C) depends on size, not color.
Answer: A
12) Cold water will warm to room temperature faster in a
A) black pot.
B) silver pot.
C) depends on size, not color.
Answer: A
13) To minimize heat loss it is best that a teapot be
A) black.
B) silver.
C) depends on size, not color.
Answer: B
14) The pupil of your eye is a net
A) absorber of radiant energy.
B) emitter of radiant energy.
C) neither
Answer: A
15) An object will normally be a net radiator of energy when its temperature is
A) higher than its surroundings.
B) lower than its surroundings.
C) neither
Answer: A
16) If air were a better conductor than it is, nighttimes on Earth would be
A) considerably colder.
B) considerably warmer.
C) not appreciably different in temperature.
Answer: A
17) If a poor absorber of radiation were a good emitter, its temperature would be
A) less than its surroundings.
B) more than its surroundings.
C) the same as its surroundings.
Answer: A
18) A good absorber of radiation is a
A) good emitter of radiation.
B) poor emitter of radiation.
C) good reflector.
D) none of the above
Answer: A
19) A good reflector of radiation is a
A) good absorber of radiation.
B) good emitter of radiation.
C) poor absorber of radiation.
D) none of the above
Answer: C
20) The Sun's radiant energy is composed of shorter wavelengths than the Earth's because the
Sun
A) has much more thermal energy.
B) has a higher temperature than the Earth.
C) is an energy source while the Earth is primarily an energy receiver.
D) none of the above
Answer: B
21) The silver coating on the glass surfaces of a Thermos bottle reduces energy that is transferred
by
A) conduction.
B) convection.
C) radiation.
D) friction.
E) none of the above
Answer: C
22) Suppose you are served coffee at a restaurant before you are ready to drink it. In order for it
to be the hottest when you are ready for it, you should add cream
A) right away.
B) at any time.
C) when you are ready to drink the coffee.
Answer: A
23) Suppose you want to save energy and you're going to leave your warm house for a half hour
on a cold day. You should turn the thermostat
A) down.
B) up.
C) off.
D) to room temperature.
Answer: C
24) Suppose you want to save energy and you're going to leave your cool house for a half hour
on a hot day. You should turn the temperature setting on the air conditioner
A) down.
B) up.
C) off.
D) to room temperature.
Answer: C
25) Explain why white clothing helps keep us cool, whereas black clothing helps to warm us.
Which is the better reflector? Which is the better absorber?
Answer: White clothing reflects all colors of light and absorbs very little of the light. It also
reflects infrared radiation. Since the energy of the infrared and light radiation is reflected away,
we are not warmed by it. Black clothing absorbs almost all of the radiation that falls on it,
infrared as well as light. The energy absorbed by black clothing is felt as heat and warms us.
26) On sunny days, why do hot-air balloons suddenly rise when they drift over a wide road or
parking lot made of black asphalt?
Answer: The air warmed by the black surface is rising, which causes the balloon to rise.
27) Why does a good emitter of heat radiation appear black at room temperature?
Answer: A good absorber of radiation is, by design, also a good emitter. This is evident when a
good absorber is not generally any warmer than poor absorbers are in the same environment.
This balance is called thermal equilibrium. A good emitter appears black at room temperatures
because the radiation it emits has too low a frequency to be seen. The rest is logic. Since a good
absorber appears black and since a good absorber is also a good emitter, it follows that a good
emitter appears black. (Heat a normally black body to incandescence, and you'll find it is a better
emitter than a nonblack body of the same temperature.)
7.4 Newton's Law of Cooling
1) Newton's law of cooling applies to objects that are
A) cooling.
B) warming.
C) both
D) none of the above
Answer: C
2) A friend says that a can of beverage will cool faster in the coldest part of a refrigerator.
Knowledge of Newton's law of cooling
A) supports this statement.
B) shows this statement is false.
C) none of the above
Answer: A
3) A can of soft drink will cool faster if placed in what part of a refrigerator?
A) the freezer compartment
B) the main part of the refrigerator
C) both locations should cool the can at the same rate
Answer: A
4) A red-hot piece of iron will cool faster in a
A) cold room.
B) warm room.
C) same in each.
Answer: A
5) Compared to a glass of ice water with ice, a glass of plain ice-cold water without ice on a
warm day will warm up
A) faster.
B) slower.
C) in the same amount of time.
Answer: A
7.5 Climate Change and the Greenhouse Effect
1) If the greenhouse effect on Earth were absent, Earth's average temperature would be about
A) -18°C.
B) appreciably warmer.
C) as it is now.
Answer: A
2) To say you can never change only one thing means that when you change something,
A) something else changes.
B) only one other thing will change.
C) you can't do it again.
Answer: A
3) Glass in a florist's greenhouse blocks radiation of
A) high frequency.
B) low frequency.
C) all frequencies.
Answer: B
4) Glass and the atmosphere are largely opaque to
A) infrared light.
B) visible light.
C) ultraviolet light.
Answer: A
5) Transparency of the atmosphere is lowest for radiation of
A) infrared light.
B) visible light.
C) ultraviolet light.
Answer: A
6) The interior of a greenhouse emits long-wavelength radiation due to its
A) green color.
B) plant cell structure.
C) transparency.
D) temperature.
Answer: D
7) Heating the Earth's atmosphere is caused by energy
A) production.
B) consumption.
C) both
D) neither
Answer: C
8) The Earth loses heat mainly by
A) conduction.
B) convection.
C) radiation.
D) none of the above
Answer: C
7.6 Heat Transfer and Change of Phase
1) Which is not a phase of matter?
A) solids
B) liquids
C) gases
D) vacuum
Answer: D
2) The molecules in a room-temperature glass of water jostle around at
A) a great variety of speeds.
B) much the same speeds.
C) constant speeds.
Answer: A
3) When evaporation occurs in a dish of water, the molecules left behind in the water
A) are less energetic.
B) have decreased average speeds.
C) result in lowered temperature.
D) none of the above
Answer: D
4) Evaporation is a cooling process because
A) heat is radiated during the process.
B) of conduction and convection.
C) the more energetic molecules are able to escape the liquid.
D) the temperature of the remaining liquid decreases.
E) none of the above
Answer: C
5) To say that evaporation is a cooling process is to say that the
A) water left behind cools.
B) surrounding air cools.
C) condensation is minimum.
Answer: A
6) Put a saucer of water on your table. A process that occurs in the saucer is
A) evaporation.
B) condensation.
C) both
D) neither
Answer: C
7) The dew that forms on a cold soda can when taken from a refrigerator is due to
A) evaporation.
B) condensation.
C) sublimation.
D) none of the above
Answer: B
8) Sublimation is a change of phase from solid to gas without
A) passing through the liquid phase.
B) a transfer of energy.
C) a change of temperature.
Answer: A
9) A mixture of light and heavy molecules make up a sample of gas. The temperature of the gas
is constant, which means all the molecules have the same average
A) speed.
B) kinetic energy.
C) both
D) none of the above
Answer: B
10) At the same temperature, which move with the greater speed in a gas?
A) light molecules
B) heavy molecules
C) both have equal average speeds
Answer: A
11) Both heavy and light molecules make up a sample of gas. On average, the faster molecules
are the
A) heavy ones.
B) light ones.
C) no difference
D) not enough information
Answer: B
12) In a gaseous mixture of hydrogen and oxygen, the higher-temperature molecules are
A) hydrogen.
B) oxygen.
C) both the same
D) not enough information
Answer: C
13) In a gaseous mixture of hydrogen and oxygen, the molecules having the greatest average
kinetic energy are
A) hydrogen.
B) oxygen.
C) both the same.
D) not enough information
Answer: C
14) In a gaseous mixture of hydrogen and oxygen, the faster molecules on average are
A) hydrogen.
B) oxygen.
C) both the same.
D) not enough information
Answer: A
15) In a gaseous mixture of hydrogen and oxygen, the slower molecules on average are
A) hydrogen.
B) oxygen.
C) both the same.
D) not enough information
Answer: B
16) If molecules in a sample of gas moved so they completely missed each other, the gas's
temperature would
A) increase.
B) decrease.
C) remain unchanged.
Answer: C
17) A hot dog pants
A) to help evaporation occur in its mouth and bronchial tract.
B) to bring more oxygen into its lungs.
C) for no particular reason–some things just happen.
D) to impress dogs of the opposite sex.
Answer: A
18) Pigs wallow in mud mainly to
A) decrease thermal conductivity.
B) shield themselves from the Sun.
C) cool themselves by evaporation.
Answer: C
19) A soda pop can with a small amount of water is on a hot stove. Soon steam comes from its
opening. When the can is quickly inverted into a pan of water, the can is crushed by
A) suction of the can interior.
B) condensation.
C) atmospheric pressure.
D) a drop in pressure.
Answer: C
20) Consider a steaming aluminum soda-pop can that contains a small amount of boiling water.
When it is quickly inverted into a bath of cooler water, the can is dramatically crushed. This is
due to the rapidly reduced pressure inside the can by
A) contact with the relatively cool water.
B) sudden slowing of the air and steam molecules inside.
C) condensation of steam inside.
D) reduced thermal energy.
E) rapid conduction of heat to the relatively cool water.
Answer: C
21) From a molecular point of view, explain why evaporation is a cooling process. What cools?
Answer: Evaporation is the change of phase from liquid to gas. The molecules in the liquid most
prone to make the transition and break through the surface to become a gas are the faster and
more energetic molecules. So the molecules that evaporate are the faster, or more energetic ones.
With selective removal of the more energetic molecules, there is a greater proportion of slower
ones left in the liquid. Hence the liquid is cooler.
22) Why does a hot dog pant?
Answer: A dog pants to cool itself by evaporation of moisture in its mouth and bronchial tract.
7.7 Boiling
1) The process of boiling water tends to
A) warm the water.
B) cool the water.
C) both warm and cool the water at the same time.
D) have no effect on water's temperature.
Answer: B
2) Boiling can be thought of as evaporation
A) beneath the surface of water.
B) at its extreme.
C) that cools instead of warming.
Answer: A
3) Boiling and freezing can occur at the same time when water is subjected to
A) decreased temperatures.
B) decreased atmospheric pressure.
C) increased temperatures.
D) increased atmospheric pressure.
Answer: B
4) When heat is added to boiling water, the water temperature
A) increases.
B) decreases.
C) remains the same.
Answer: C
5) Increased air pressure on the surface of hot water tends to
A) prevent boiling.
B) promote boiling.
C) neither
Answer: A
6) In the mountains, water boils at
A) a higher temperature than at sea level.
B) a lower temperature than at sea level.
C) the same temperature as at sea level.
Answer: B
7) When salt is introduced to water, the temperature at which freezing occurs is
A) quite unaffected.
B) lowered.
C) increased.
D) dependent on the shape of salt and ice crystals.
Answer: B
8) Food is cooked faster in a pressure cooker because of the
A) higher temperature.
B) greater rate of bubble formation in the water.
C) increased thermal energy in the water.
D) none of the above
Answer: A
9) Food in boiling water cooks slower in high-altitude locations. If you increase the temperature
under the pot the food will cook
A) faster.
B) slower.
C) neither
Answer: C
10) If you want to cook eggs by boiling them while in the mountains, then compared with
cooking at sea level you should
A) use a hotter flame.
B) boil the eggs for a shorter time.
C) boil the eggs for a longer time.
D) none of the above
Answer: C
11) When bringing water to a boil in the mountains, the time needed to reach the boiling point is
A) less than at sea level.
B) more than at sea level.
C) the same as at sea level.
Answer: A
7.8 Melting and Freezing
1) Keep increasing the shaking of atoms in a solid and it will
A) melt.
B) sublime.
C) harden.
Answer: B
2) Melting and freezing are both
A) changes of phase.
B) opposite processes.
C) processes of molecular transfer.
D) all of the above
Answer: D
3) Keep decreasing the shaking of atoms in a liquid and it will
A) melt.
B) harden.
C) solidify.
Answer: C
4) When water changes to ice, water molecules
A) absorb energy.
B) release energy.
C) retain their energy.
D) lose the quality of wetness.
Answer: B
5) When ice changes phase to become water, energy is
A) absorbed.
B) released.
C) unchanged.
Answer: A
6) An researcher discovers a harmless and tasteless salt, which, when added to water changes its
boiling point. The market value for this salt will be best if the salt
A) lowers the boiling point of water.
B) raises the boiling point of water.
C) either
Answer: B
7) Why is a steam burn more damaging than a burn by boiling water of the same temperature?
Answer: When steam comes in contact with the skin, condensation occurs, accompanied by a
large release of energy. After the energy release (about 540 calories per gram of steam), what is
left is water at the temperature of boiling. So more energy is transferred to the skin when burned
with steam than with water at the same temperature.
7.9 Energy and Change of Phase
1) Which requires more energy?
A) melting a gram of 0°C ice
B) increasing the temperature of 1 gram of water from 0°C to 100°C
C) changing 1 gram of 100°C water to 100°C steam
D) all the same
Answer: C
2) Which would burn the most?
A) 100 g of water at 100°C
B) 100 g of steam at 100°C
C) both equal
Answer: B
3) Steam burns are much more damaging than boiling-water burns because steam
A) has a higher temperature.
B) contains more thermal energy.
C) is hotter.
D) is gaseous.
Answer: B
4) Steam burns are more damaging than burns caused by boiling water because steam
A) releases additional energy when it condenses.
B) has more energy per kilogram than boiling water.
C) both
D) neither
Answer: C
5) When steam condenses to water, energy is
A) absorbed.
B) released.
C) conserved as the phase change occurs.
D) transformed to a different form.
Answer: B
6) When a gas is changed to a liquid phase, the gas
A) releases energy.
B) absorbs energy.
C) neither
Answer: A
7) When a solid is changed to a liquid phase, the solid
A) releases energy.
B) absorbs energy.
C) neither releases nor absorbs energy.
Answer: B
8) When gases change to a liquid phase, they
A) absorb energy.
B) release energy.
C) neither absorb nor release energy.
Answer: B
9) We feel uncomfortably warm on a muggy day because water molecules are
A) evaporating from our moist bodies.
B) condensing on our bodies.
C) preventing the evaporation from our moist bodies.
Answer: B
10) We are warmed by condensation because water molecules in the air striking our bodies
A) transfer some of their kinetic energies to us.
B) gain kinetic energy as they change state.
C) form an insulating layer on our bodies.
Answer: A
11) When snow forms in clouds, the surrounding air is
A) cooled.
B) warmed.
C) cooled and warmed.
D) none of the above
Answer: B
12) When a gas changes phase to become a solid, energy is
A) absorbed.
B) released.
C) unchanged.
Answer: B
13) Suppose you walk on red hot coals with bare feet. Providing bits of coal do not stick to your
feet, it would be safer if your feet are
A) wet.
B) dry.
C) either
Answer: A
14) To melt 50 g of 0°C ice requires
A) 25 calories.
B) 50 calories.
C) 80 calories.
D) none of the above
Answer: D
15) To change 50 g of boiling water to steam requires
A) 50 calories.
B) 500 calories
C) 540 calories.
D) more calories than is required to bring 50 g of ice at absolute zero to the boiling point.
E) none of the above
Answer: D
16) The number of grams of ice that can be melted by 1 g of 100°C steam is
A) 0.125 g.
B) 0.148 g.
C) 6.75 g.
D) 8 g.
E) none of the above
Answer: D
Test Bank for Conceptual Physical Science
Paul Hewitt, John Suchocki, Leslie Hewitt
9780321752932, 9780134060491
