P199 Homework 7

If the greenhouse effect on Earth were absent, Earth's average temperature would be about

-18°C.

Put a saucer of water on your table. A process that occurs in the saucer is

-condensation. -evaporation.

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

-has more energy per kilogram than boiling water. -releases additional energy when it condenses.

Melting and freezing are both

-opposite processes. -changes of phase. -processes of molecular transfer.

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

-pressure. -density.

Heating the Earth's atmosphere is caused by energy

-production. -consumption.

If an object radiates more energy than it absorbs, its

-temperature decreases. -thermal energy decreases.

Radiant energy emitted by our planet is

-the result of radioactivity in Earth's interior. -electromagnetic. -terrestrial energy.

If an object radiates more energy than it reflects, its

-thermal energy decreases. -temperature decreases.

Newton's law of cooling applies to objects that are

-warming. -cooling.

Boiling can be thought of as evaporation...

...beneath the surface of water.

Which would burn the most? 100 g of water at 100°C or 100 g of steam at 100°C

100 g of steam at 100°C

From best to worst, rank these materials as heat conductors: (a) copper wire, (b) snow, and a (c) glass rod.

A (Copper wire)- best. C (Glass). B (Snow)- Worst.

Which requires more energy? A. changing 1 gram of 100°C water to 100°C steam B. melting a gram of 0°C ice C. increasing the temperature of 1 gram of water from 0°C to 100°C

A. changing 1 gram of 100°C water to 100°C steam

A block of ice at 0∘C is dropped from a height that causes it to completely melt upon impact. Assume that there is no air resistance and that all the energy goes into melting the ice. A. What is the height necessary for this to occur. [ Hint: Equate the joules of gravitational potential energy to the product of the mass of ice and its heat of fusion (Lf = 335,000 J/kg).]. B. Does the answer depend on mass?

A. h = 34 km. B. No.

A 5.0-kg iron ball is dropped onto a pavement from a height of 100 m . Suppose that half of the heat generated goes into warming the ball. A. What is the temperature increase of the ball. (The specific heat capacity of iron is 450 J/kg ⋅ ∘C. Use 9.8 N/kg for g.). B. Is the answer the same for an iron ball of any mass?

A. ΔT = 1.1 ∘C B. Yes.

From greatest to least, rank the energy needed for these phase changes for equal amounts of H2O: (a) from ice to ice water, (b) from ice-water to boiling water, and (c) from boiling water to steam.

C (boiling water to steam)- Greatest. B (ice-water to boiling water). A (Ice to ice water)- Least.

Find what heat in calories (cal) is required to increase the temperature of 60 g water from 0∘C to 95 ∘C. The specific heat capacity of water is 1 cal/g⋅∘C.

Q = 5700 cal

If molecules in a sample of gas moved so they completely missed each other, the gas's temperature would

Remain unchanged.

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

a great variety of speeds.

In the mountains, water boils at

a lower temperature than at sea level.

The gush of steam that issues from the escape valve of a pressure cooker is relatively cool

above the opening where expansion is prominent.

Objects that are good radiators generally

absorb radiation relatively well.

When ice changes phase to become water, energy is

absorbed.

The pupil of your eye is a net

absorber of radiant energy.

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

absorbs energy.

Alcohol evaporates faster than water at the same temperature. Which cools your skin more: alcohol, or the same amount of water, evaporating from your skin?

alcohol.

If you were caught in freezing weather with only a candle for warmth, you would be warmer in

an igloo.

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

atmospheric pressure.

Cold water will warm to room temperature faster in a

black pot.

Hot water will cool to room temperature faster in a

black pot.

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

boil the eggs for a longer time.

In a gaseous mixture of hydrogen and oxygen, the higher-temperature molecules are

both the same.

In a gaseous mixture of hydrogen and oxygen, the molecules having the greatest average kinetic energy are

both the same.

A red-hot piece of iron will cool faster in a

cold room.

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

condensation of steam inside.

The dew that forms on a cold soda can when taken from a refrigerator is due to

condensation.

If air were a better conductor than it is, nighttimes on Earth would be

considerably colder.

Steam burns are much more damaging than boiling-water burns because steam

contains more thermal energy.

Coastal winds shift from night to day due to

convection.

The process of boiling water tends to

cool the water.

Pigs wallow in mud mainly to

cool themselves by evaporation.

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

cooler.

Hot steam that issues from a pressure cooker expands and

cools.

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

cools.

Boiling and freezing can occur at the same time when water is subjected to

decreased atmospheric pressure.

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

faster.

The process of convection occurs in

fluids.

Which is not a phase of matter?

gases liquids **vacuum** solids

A good absorber of radiation is a

good emitter of radiation.

A poor conductor of heat is a

good insulator.

The Sun's radiant energy is composed of shorter wavelengths than the Earth's because the Sun

has a higher temperature than the Earth.

The higher the temperature of an object, the

higher frequency it radiates.

Food is cooked faster in a pressure cooker because of the

higher temperature.

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

higher than its surroundings.

In a gaseous mixture of hydrogen and oxygen, the faster molecules on average are

hydrogen.

When a volume of air is compressed, its temperature

increases.

Glass and the atmosphere are largely opaque to

infrared light.

Transparency of the atmosphere is lowest for radiation of

infrared light.

Your toes feel warmer on a rug than on a tile floor because the rug

is a better insulator than tile.

The average frequency of radiant energy is directly proportional to the

kelvin temperature of the emitter.

A star that is twice as hot as another has twice the

kelvin temperature.

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

kinetic energy.

When bringing water to a boil in the mountains, the time needed to reach the boiling point is

less than at sea level.

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

less than its surroundings.

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

light molecules.

Both heavy and light molecules make up a sample of gas. On average, the faster molecules are the

light ones.

Metals are both good heat and electrical conductors due to

looseness of outer electrons in metal atoms.

Glass in a florist's greenhouse blocks radiation of

low frequency.

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

low thermal conductivity of the coals.

When salt is introduced to water, the temperature at which freezing occurs is

lowered.

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

off.

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

off.

In a gaseous mixture of hydrogen and oxygen, the slower molecules on average are

oxygen.

Sublimation is a change of phase from solid to gas without

passing through the liquid phase.

A good reflector of radiation is a

poor absorber of radiation.

A good heat conductor is a

poor insulator.

Increased air pressure on the surface of hot water tends to

prevent boiling.

The Earth loses heat mainly by

radiation.

The silver coating on the glass surfaces of a Thermos bottle reduces energy that is transferred by

radiation.

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

raises the boiling point of water.

When water changes to ice, water molecules

release energy.

When steam condenses to water, energy is

released.

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

releases energy.

When heat is added to boiling water, the water temperature

remains the same.

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

right away.

The higher the frequency of a wave, the

shorter the wavelength.

The higher the temperature of an object, the

shorter the wavelengths it radiates.

To minimize heat loss it is best that a teapot be

silver.

A good insulator

slows heat transfer.

Keep decreasing the shaking of atoms in a liquid and it will

solidify.

To say you can never change only one thing means that when you change something,

something else changes.

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

supports this statement.

The interior of a greenhouse emits long-wavelength radiation due to its

temperature.

A can of soft drink will cool faster if placed in what part of a refrigerator?

the freezer compartment

Evaporation is a cooling process because

the more energetic molecules are able to escape the liquid.

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

the paper cup cannot become appreciably hotter than the water it contains.

A hot dog pants

to help evaporation occur in its mouth and bronchial tract.

Convection currents in the air near a seashore are produced by

unequal heating of land and water.

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

water left behind cools.