Deck 9: Heat Transfer and Change of Phase

Question 1

The cooling effect inside a refrigerator is produced by

A) an electric motor that converts electrical energy into internal energy.
B) vaporizing the refrigeration liquid.
C) replacing the warmer air with colder air.
D) compressing the refrigeration gas into a liquid.
E) proper insulation.

Answer 1

vaporizing the refrigeration liquid.

Question 2

A good heat conductor is

A) a good insulator.
B) a poor insulator.
C) neither a poor nor a good insulator.

Answer 2

a poor insulator.

Question 3

When water vapor condenses on the inside of a window, the room becomes slightly

A) cooler.
B) warmer.
C) neither warmer nor cooler.

Answer 3

warmer.

Question 4

To turn ice at zero degrees Celsius to water at zero degrees Celsius, we must add

A) energy.
B) time.
C) force.
D) temperature.
E) It can't be done - water is always warmer than that.

Question 5

When snow forms in clouds, the surrounding air

A) cools.
B) warms.
C) neither warms nor cools.

Question 6

Morning dew on the grass is a result of

A) slow-moving water molecules sticking to one another.
B) the open-structured form of water crystals.
C) evaporation of water.
D) air pressure on water vapor.

Question 7

An object will normally be a net radiator of energy when its internal energy is

A) more than that of its surroundings.
B) less than that of its surroundings.
C) neither of these, because internal energy is not temperature.

Question 8

You can briefly touch a hot clothes iron with a bare wet finger because the wetness

A) Choices C and D are both true.
B) Only Choice C is true.
C) absorbs energy in vaporizing.
D) provides an insulating layer after it changes state.

Question 9

The minimum amount of 100-degree-C steam needed to melt 1 gram of 0-degree-Celsius ice is

A) 0.125 gram.
B) 6.75 grams.
C) 0.148 gram.
D) 8 grams.
E) none of these

Question 10

Compared to a glass of icewater with ice in it, 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.
D) None of the above choices are true.

Question 11

Hydrogen and oxygen molecules in a gas sample have the same temperature. This means the hydrogen molecules, on the average, have the same

A) kinetic energy, but more speed.
B) speed, but more kinetic energy.
C) speed, but less kinetic energy.
D) speed and the same kinetic energy.
E) kinetic energy, but less speed.

Question 12

For increased atmospheric pressure, the boiling temperature of a liquid

A) remains at 100 degrees C.
B) goes down.
C) goes up.

Question 13

To increase the temperature of 50 grams of water by 2 Celsius degrees requires

A) 0.04 calorie.
B) 25 calories.
C) 100 calories.
D) 2 calories.
E) 4.18 calories.

Question 14

At the same temperature, which move with the greater speed in the air?

A) heavier molecules
B) very light molecules
C) All will have equal average speeds.

Question 15

Newton's law of cooling applies to objects that are

A) heating.
B) cooling.
C) both of these
D) none of these

Question 16

To turn 50 grams of boiling water to steam requires

A) 540 calories.
B) 50 calories.
C) 500 calories
D) more calories than are required to bring 50 grams of ice at absolute zero to the boiling point.
E) None of the above choices are correct.

Question 17

Metals are both good heat conductors and good electrical conductors because of the

A) ability of metals to transfer energy easily.
B) relatively high densities of metals.
C) looseness of outer electrons in metal atoms.
D) high elasticity of metals.
E) similarity between thermal and electrical conductive properties.

Question 18

Evaporation is a cooling process and condensation is

A) a cooling process also.
B) a warming process.
C) neither a warming nor cooling process.

Question 19

Warm air rises because faster-moving molecules tend to move to regions of less

A) density and less pressure.
B) pressure.
C) density.

Question 20

Double the absolute temperature of helium gas and the average speed of its molecules

A) more than doubles.
B) doubles.
C) less than doubles.

Question 21

The reason the sun's radiant energy is of shorter wavelengths than the Earth's is because the sun

A) has a higher temperature than the Earth.
B) has much more internal energy.
C) is an energy source while the Earth is primarily an energy receiver.
D) all of these
E) none of these

Question 22

Increased air pressure on the surface of hot water tends to

A) prevent boiling .
B) promote boiling.
C) Neither choice A nor choice B is true.
D) Choice A and choice B are both true.

Question 23

Waves emitted by the sun and terrestrial wave emissions are

A) the same except for their frequencies and wavelengths.
B) entirely different kinds of waves.
C) identical.

Question 24

The molecules in a room-temperature glass of water jostle around at

A) a very small range of speeds.
B) a great variety of speeds.
C) much the same rates of speed.

Question 25

Water will evaporate quicker if it

A) Choices C, D, and E are all correct.
B) One or two of the choices below are not correct.
C) is spread out in a thin sheet.
D) is surrounded by dry air.
E) is preheated to 100 degrees C.

Question 26

On a humid day, water condenses on the outside of a glass of ice water. This phenomenon occurs mainly because of

A) the porosity of glass.
B) adhesion of water molecules to glass.
C) the saturation of cooled air.
D) capillary action.
E) evaporation.

Question 27

If a volume of air is warmed, it expands. If a volume of air expands, it

A) cools.
B) warms.
C) neither warms nor cools.

Question 28

We feel uncomfortably warm on a muggy day because water molecules are

A) evaporating from our moist bodies.
B) condensing on our bodies.
C) evaporating and condensing on our bodies at the same rate.

Question 29

Steam burns are more damaging than burns caused by boiling water because steam

A) gives up additional energy when it condenses.
B) has more energy per kilogram than boiling water.
C) Choices A and B are both correct.
D) Choices B and C are both incorrect.

Question 30

If air were a better conductor than it is, at nighttime the Earth would be

A) considerably warmer.
B) considerably colder.
C) not appreciably different in temperature.

Question 31

The food in a refrigerator is cooled by

A) vaporization of the refrigerating fluid.
B) condensation of the refrigerating fluid.
C) the ice in your nearby freezer.

Question 32

Objects that radiate relatively well,

A) absorb radiation relatively well.
B) reflect radiation relatively well.
C) both of these
D) neither of these

Question 33

To say that evaporation is a cooling process is to say that the

A) the less energetic particles escape.
B) more energetic particles remain in the water.
C) more energetic particles escape.

Question 34

Which involves the larger number of calories?

A) the condensation of 1 gram of steam at 100 degrees Celsius to water at 100 degrees
B) the cooling of 1 gram of water at 100 degrees Celsius to 1 gram of ice at absolute zero
C) Both involve the same number of calories.
D) Neither involves calories.

Question 35

Energy transfer by convection is primarily restricted to

A) gases.
B) liquids.
C) fluids.
D) solids.
E) none of these

Question 36

When liquids change to a solid state, they

A) release energy.
B) absorb energy.
C) neither absorb nor release energy.
D) both absorb and release energy.

Question 37

Increase the pressure in a container of oxygen gas while keeping the temperature constant and you increase the

A) molecular kinetic energy.
B) molecular speed.
C) Choice A and choice B are both true.
D) Neither choice A or choice B is true.

Question 38

The planet Earth loses heat mainly by

A) conduction.
B) radiation.
C) convection.
D) all of these

Question 39

A substance can be sprayed on crops to prevent frost formation under many conditions. If frost did not form on the fields and woods of an entire continent, cold nights would be

A) less cold.
B) even colder.
C) no different.

Question 40

One of the main reasons one can walk barefoot on red-hot coals of wood without burning the feet has to do with

A) low thermal conductivity of the coals.
B) low temperature of the coals.
C) mind over matter techniques.

Question 41

The operation of a geyser, such as Old Faithful in Yellowstone park, is most like the operation of a

A) canteen.
B) vat of molten lead.
C) coffee percolator.
D) teakettle.
E) vacuum bottle.

Question 42

Both black and white road surfaces radiate energy. At the end of a starry night the warmer road surface will be

A) the white surface.
B) the black surface.
C) neither-there is no difference.

Question 43

Ice is put in a cooler to cool the contents. To speed up the cooling process, the ice can be

A) drained of ice water periodically.
B) wrapped in newspaper.
C) kept out of contact with the food.
D) kept in one solid chunk.
E) covered with salt.

Question 44

Substances absorb heat energy by the process of

A) radiation.
B) convection.
C) conduction.
D) all of these

Question 45

Cold water will warm to room temperature faster in a

A) black pot.
B) silver pot.
C) depends more on the size of the pots than their color

Question 46

If a poor absorber of radiation were a good emitter, its temperature would be

A) less than its surroundings.
B) the same as its surroundings.
C) more than its surroundings.

Question 47

Evaporation is a cooling process because

A) heat is radiated during the process.
B) the temperature of the remaining liquid decreases.
C) of conduction and convection.
D) the more energetic molecules are able to escape the liquid.
E) none of these

Question 48

The mass of ice that can be melted by 1 gram of 100-degree-C steam is (Hint: Don't forget about hot water remaining from condensed steam)

A) 0.148 gram.
B) 6.75 grams.
C) 0.125 gram.
D) 8 grams.
E) none of these

Question 49

To melt 50 grams of 0-degree-Celsius ice requires

A) 50 calories.
B) 80 calories.
C) 25 calories.
D) none of these

Question 50

A Thermos bottle has double glass walls with silver coating on the glass surfaces that face one another. The silver coating reduces the energy that is transferred by

A) radiation.
B) convection.
C) conduction.
D) friction.
E) none of these

Question 51

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) to room temperature.

Question 52

In a mixture of hydrogen gas, oxygen gas, and nitrogen gas, the molecules with the greatest average speed are those of

A) nitrogen.
B) hydrogen.
C) oxygen.
D) All will have the same average speed at the same temperature.

Question 53

An object will normally be a net radiator of energy when its temperature is

A) lower than its surroundings.
B) higher than its surroundings.
C) neither of these

Question 54

The calories needed to change 10 grams of ice at zero degrees C to steam at 100 degrees C is

A) 6200.
B) 7200.
C) 6400.
D) 8000.
E) None of the above choices are correct.

Question 55

A good reflector of radiation is

A) good emitter of radiation.
B) poor absorber of radiation.
C) good absorber of radiation.
D) none of these

Question 56

Both black and white road surfaces absorb sunlight. At the end of a sunny day the warmer road surface will be

A) the white surface.
B) the black surface.
C) neither-there is no difference.

Question 57

If you want to cook eggs by boiling them while in the mountains, then compared to sea-level cooking, you should

A) boil the eggs for a shorter time.
B) boil the eggs for a longer time.
C) use a hotter flame.
D) None of the above choices are true.

Question 58

An inventor 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 raises or lowers the boiling point, as the food would be cooked either way.

Question 59

When a volume of air is compressed, its temperature

A) increases.
B) decreases.
C) neither increases nor decreases.

Question 60

The technology for orbiting solar power plants

A) already exists.
B) awaits the next century.
C) is theoretically impossible.

Question 61

If you double the pressure of an ideal gas while keeping the temperature constant, the average kinetic energy of the molecules

A) increases by more than twice.
B) increases by less than twice.
C) remains unchanged.
D) is doubled.

Question 62

A liter of hot water will cool to room temperature faster in a

A) silver pot.
B) red pot.
C) black pot.
D) depends more on the size of the pot than its color

Question 63

Wrapping a hot potato in aluminum foil significantly reduces the rate at which it loses energy by

A) conduction.
B) radiation.
C) convection.

Question 64

Stored potatoes, beets, and rutabagas in a well-insulated but unheated room can be protected from freezing by having in the room

A) large tubs of water.
B) large blocks of salt.
C) large rocks.
D) large blocks of foam plastic.
E) large cubes of sugar.

Question 65

Food cooked in boiling water at a mountain top cooks slower than when cooked at sea level. If the temperature under the pot of boiling water is increased, the food will cook

A) faster at the mountain top.
B) faster at sea level.
C) faster at both places.
D) no differently than it did before the increase.

Question 66

The pupil of your eye is

A) a net absorber of radiant energy.
B) a net emitter of radiant energy.
C) neither a net absorber or emitter of radiant energy.

Question 67

When heat is added to boiling water, its temperature

A) increases.
B) decreases.
C) does not change.

Question 68

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) off altogether.
B) up a little.
C) to room temperature.
D) down a little.

Question 69

Firefighters find that the temperature of burning material is best lowered when water is

A) pointed away from the flames.
B) salted.
C) sprayed as a fine mist.
D) used in small amounts.

Question 70

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.

Question 71

When a block of ice at zero degrees Celsius melts, the ice

A) releases energy and gets warmer.
B) absorbs energy and gets warmer.
C) releases energy to its environment.
D) absorbs energy from its environment.
E) absorbs energy but does not change its temperature.

Question 72

A good absorber of radiation is a

A) good emitter of radiation.
B) good reflector.
C) poor emitter of radiation.
D) none of these

Question 73

A water-filled paper cup held in a flame will not catch fire. This is because

A) water is an excellent conductor of heat.
B) the inside of the paper is wet.
C) paper is a poor conductor of heat.
D) the paper cup cannot become appreciably hotter than the water it contains.

Question 74

It is commonly thought 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 common knowledge.
B) shows this common knowledge is false.
C) supports or contradicts this common knowledge.

Question 75

The higher the temperature of an object,

A) the longer the wavelengths it radiates.
B) the shorter the wavelengths it radiates.
C) makes no difference in the wavelengths it radiates

Question 76

Wrapping a hot potato in aluminum foil significantly reduces the rate at which it cools by

A) conduction.
B) evaporation.
C) condensation.
D) melting.

Question 77

If a solid object radiates more energy than it absorbs, its

A) internal energy decreases.
B) temperature decreases.
C) internal energy and temperature decrease.
D) None of the above choices are true.

Question 78

Which body glows with electromagnetic waves?

A) both the Sun and the Earth
B) only the Sun
C) only the Earth
D) neither the Sun or the Earth

Question 79

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.

Question 80

Suppose you walk on red-hot coals with bare feet. If bits of the coals do not stick to your feet, it would be best if your feet are

A) very hot.
B) warm.
C) dry.
D) wet.
E) cold.