Chapter 17: Change of Phase

Question 1

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

Answer 1

gives up change of phase energy when it condenses and has more energy per kilogram than boiling water

Question 2

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

Answer 2

releases energy

Question 3

As atmospheric pressure is increased, the boiling temperature of a liquid

Answer 3

goes up

Question 4

If we slowly pump out all the air over a bowl of water until it is in a vacuum,

Answer 4

it will boil, then freeze

Question 5

Food in a pressure cooker is cooked faster because of the

Answer 5

higher temperatures reached in a sealed container.

Question 6

Adding pressure to ice causes ice to

Answer 6

melt

Question 7

Near the top of a mountain, water in an open pot boils at

Answer 7

a lower temperature than at sea level

Question 8

The food in a refrigerator is cooled by

Answer 8

vaporization of the refrigerating fluid

Question 9

Compared to a glass of ice water with ice in it, on a warm day a glass of pure ice-cold water without ice will warm up

Answer 9

faster

Question 10

If you heat an ice bucket of water for several hours until only a small amount of ice remains, the temperature of water will be

Answer 10

0° C

Question 11

When warm air rises, it

Answer 11

expands and cools

Question 12

If you add heat for 35 minutes to a pan with 2 kgs of 100°C water in it the temperature of the remaining water will be

Answer 12

100°C

Question 13

How many joules does it takes to vaporize 1 gram of water?

Answer 13

2255 J (sometimes rounded up to 2260 J)

Question 14

When water in the vapor phase condenses to liquid in the air, the surrounding air

Answer 14

warms

Question 15

When the air pressure is lowered,

Answer 15

it takes less heat to boil water

Question 16

The change of phase from liquid to gaseous?

Answer 16

Evaporation

Question 17

The change of phase from solid to gaseous, bypassing the liquid phase?

Answer 17

Sublimation

Question 18

The change of phase from gaseous to liquid?

Answer 18

Condensation

Question 19

Rapid evaporation that takes place within a liquid as well as at its surface?

Answer 19

Boiling

Question 20

The process of melting under pressure and the subsequent refreezing when the pressure is removed?

Answer 20

Regelation

Question 21

A device that transfers heat out of a cool environment and into a warm environment?

Answer 21

Heat pump

Question 22

The amount of energy required to change a unit mass of a substance from solid to liquid (and released in the reversed process).

Answer 22

Latent heat of fusion

Question 23

The amount of energy required to change a unit mass of a substance from liquid to gas (and released in the reverse process).

Answer 23

Latent heat of vaporization

Question 24

A solid must _______ energy to _______.

Answer 24

A solid must absorb energy to melt.

Question 25

A liquid must _______ energy to _______.

Answer 25

A liquid must absorb energy to vaporize.

Question 26

A gas must _______ energy to ________.

Answer 26

A gas must release energy to liquify.

Question 27

A liquid must _______ energy to ________.

Answer 27

A liquid must release energy to solidify.

Question 28

When H2O in the vapor phase condenses, is the surrounding air warmed or cooled?

Answer 28

Warmed. The change of phase is from vapor to liquid, which releases energy, so the surrounding air is warmed.

Question 29

One calorie is equal to how many joules?

Answer 29

4.187 joules

Question 30

Heat of ___________ is either the energy required to separate molecules from the liquid phase or the energy released when gas condenses to the liquid phase.

Answer 30

vaporization

Question 31

Heat of _______ is either the energy needed to separate molecules from the solid phase or the energy released when bonds form in a liquid that change it to the solid phase.

Answer 31

fusion

Question 32

______ has more potential energy because the molecules are relatively free of each other and are not bound together as in the liquid phase.

Answer 32

Steam

Question 33

How much energy is transferred when 1 g of steam at 100 degrees C condenses to water at 100 degrees C?

Answer 33

540 calories of energy. One gram of steam at 100 degrees C transfers 540 calories of energy when it condenses to become water at same temperature.

Question 34

How much energy is transferred when 1 g of boiling water at 100 degrees C cools to ice water at 0 degrees C?

Answer 34

100 calories. One gram of boiling water transfers 100 calories when it cools 100 degrees C to become ice water.

Question 35

How much energy is transferred when 1 g of ice water at 0 degrees C freezes to ice at 0 degrees C?

Answer 35

80 calories. One gram of ice water at 0 degrees C transfers 80 calories to become ice at 0 degrees C.

Question 36

How much energy is transferred when 1 g of steam at 100 degrees C turns to ice at 0 degrees C?

Answer 36

720 calories. One gram of steam at 100 degrees C transfers to the surroundings 720 calories to become ice at 0 degrees C.

Question 37

If 4 g of boiling water is poured onto a cold surface and 1 g rapidly evaporates, if evaporation takes 540 calories from the remaining 3 g of water and no other heat transfer takes place, what will be the temperature of the remaining 3 g?

Answer 37

0 degrees C. The remaining 3 g will turn into 0 degree C ice.

Question 38

When snow forms in clouds, the surrounding air is ________.

Answer 38

warmed (the change of phase is from gas to solid which releases energy).

Question 39

Which involves the greatest number of calories: a) Condensing 1 g of 100 degree C steam to 100 degree C water; b) Cooling 1 g of 100 degree C water to 1 gram of 0 degree C ice; c) Cooling 1 g of 0 degree C ice to near absolute zero; d) All about the same

Answer 39

a) Condensing 1 g of 100 degree C steam to 100 degree C water, which takes 540 calories.

Question 40

Ice is put in a picnic cooler. To speed up the cooling of cans of beverage, it is important that the ice: a) melts; b) is prevented from melting; c) be in large chunks; d) None of the above

Answer 40

a) melts; For each gram of ice that melts, 80 calories is taken from the beverage.

Question 41

Boiling point is lower with

Answer 41

lower atmospheric pressure

Question 42

The process of boiling: a) cools the water being boiled; b) depends on atmospheric pressure; c) is a change of phase below the water surface; d) All of the above

Answer 42

d) All of the above