Deck 17: Change of Phase

Question 1

Which could burn a boy scout the most?

A)100 g of water at 100 degrees C
B)100 g of steam at 100 degrees C
C)Both would be equally damaging.

Answer 1

100 g of steam at 100 degrees C

Question 2

Evaporation is a cooling process and condensation is

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

Answer 2

a warming process.

Question 3

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.

Answer 3

condensing on our bodies.

Question 4

Boiling water does not increase in temperature when additional heat is applied because

A)the temperature doesn't change in a Change of Phase.
B)added input energy doesn't increase the water's internal energy.
C)the increased heating produces increased boiling,and therefore increased cooling.
D)none of these

Question 5

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

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

Question 6

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 7

When a gas is changed to a liquid state,the gas

A)releases energy.
B)absorbs energy.
C)neither releases nor absorbs energy.
D)both releases and absorbs energy.

Question 8

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.

Question 9

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 10

When liquids change to a solid state,they

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

Question 11

When heat is added to boiling water,its temperature

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

Question 12

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

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

Question 13

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 these

Question 14

When a solid is changed to a liquid state,the solid

A)releases energy.
B)absorbs energy.
C)neither releases nor absorbs energy.
D)both releases and absorbs energy.

Question 15

For increased atmospheric pressure,the boiling temperature of a liquid

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

Question 16

We are warmed by condensation because water molecules in the air that strike our bodies

A)transfer some of their kinetic energy to us.
B)gain kinetic energy as they change state.
C)form an insulating layer on our bodies.

Question 17

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 18

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

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

Question 19

Near the top of a mountain,water in an open pot 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.
D)None of the above choices are true.

Question 20

Hot water has a relatively high rate of

A)evaporation.
B)condensation.
C)conductivity.
D)convection.

Question 21

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

Question 22

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

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

Question 23

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

Question 24

An inventor discovers a harmless and tasteless salt,which changes its boiling point when added to water.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 25

Use the following figure to answer the question:
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 26

Melting snow

A)warms the surrounding air.
B)cools the surrounding air.
C)neither warms nor cools the surrounding air.

Question 27

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

Question 28

To turn 50 grams of boiling water to steam requires

A)50 calories.
B)500 calories
C)540 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 29

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 30

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

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

Question 31

The cooling effect inside a refrigerator is produced by

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

Question 32

When snow forms in clouds,the surrounding air

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

Question 33

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

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

Question 34

Compared to a glass of ice water 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 35

Use the following figure to answer the question:
Food in a pressure cooker is cooked faster because of the

A)higher temperature.
B)greater rate of bubble formation in the water.
C)increased internal energy in the water.
D)Choices A,B,and C are all true.

Question 36

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

A)0)04 calorie.
B)2 calories.
C)4)18 calories.
D)25 calories.
E)100 calories.

Question 37

A refrigerator

A)produces cold.
B)causes internal energy to disappear.
C)removes internal energy from inside the refrigerator.
D)changes heat into cold.
E)none of these

Question 38

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

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

Question 39

Use the following figure to answer the question:
The phenomenon of regelation depends on the

A)freezing point of water.
B)melting point of water.
C)open-structured nature of ice crystals.
D)high specific heat of water.

Question 40

Morning dew on the grass is a result of

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

Question 41

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

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

Question 42

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

A)0)125 gram.
B)0)148 gram.
C)6)75 grams.
D)8 grams.
E)none of these

Question 43

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

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

Question 44

Stored potatoes,beets,and rutabagas freeze at temperatures below zero degrees Celsius (rather than at exactly zero)because

A)they are good radiators of energy.
B)they are good absorbers of radiant energy.
C)the water in them contains dissolved salts and sugars.
D)they are very dense.
E)All of the above choices are true.

Question 45

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 by atmospheric pressure.This occurs because the pressure inside the can is rapidly reduced 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 internal energy.
E)rapid conduction of heat to the relatively cool water.

Question 46

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

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

Question 47

A factor that usually determines whether a substance is in the solid,liquid,gaseous,or plasma state is its

A)composition.
B)atomic number.
C)atomic shell configuration.
D)temperature.
E)none of these

Question 48

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 49

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

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

Question 50

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)125 gram.
B)0)148 gram.
C)6)75 grams.
D)8 grams.
E)none of these

Question 51

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

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

Question 52

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.