Physics: Thermodynamics

A copper rod has one of its ends placed in a Bunsen flame and the other end embedded in an ice cube. By what factor is the rate of heat flow changed when the rod length is tripled?

0.33

Which would burn the most

100g of steam at 100C

At what temperature is water most dense?

4 C

What is the theoretical efficiency of a Carnot engine that operates between 600K and 300K?

50%

If you triple the absolute temperature of an object, it will radiate energy

81 times faster

The Kelvin temperature scale has the same size degrees as the --- scale and its zero is --- degrees lower

Celsius ... 273

The space between the inner walls of a Thermos bottle is evacuated to minimize heat transfer by

Conduction and convention

A substance can absorb heat energy by the process of

Conduction, convection, radiation, and evaporation *the answer for the question is all of the above

When a vapor condenses

Heat energy leaves the substance

Which heat is the greatest?

Heat necessary to vaporize 1kg of boiling water

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

Neither of these *not faster or slower

Convection can occur

Only in liquids and gases

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

Transfer some of their kinetic energies to us

By blowing on a cup of hot coffee

We remove water vapor above the coffee so that further evaporation is enhanced

Is it possible to transfer heat from a cold reservoir to a hot reservoir?

Yes, but work will have to be done

In the mountains, water boils at

a lower temperature than at sea level

Objects that radiate relatively well

absorb radiation relatively well

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

absorbs energy

Saturation occurs in air when the

air contains as many as water molecules as it can contain at a given temperature

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

an igloo

Heat engines, such as automobile engines, are more efficient when run

at high temperatures

As entropy of a system increases, energy in the system

becomes more diluted

Cold water will warm to room temperature faster in a

black pot

Hot water will cool at room temperature faster in a

black pot

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

boil the eggs for a longer time

A heat pump

can act as a heater, can act as an air conditioner, is a reversible heat engine, and works well only in moderate climates *the answer is all of the above

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

can't say, because thermal energy is not temperature

Which material is a good thermal insulator?

concrete

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

condensation of steam inside

By what primary heat transfer mechanism does one end of a metal spoon become hot when the other end is placed in boiling water?

conduction

The space between the inner walls of a thermos bottle is evacuated to minimize heat transfer by

conduction and convection

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

considerably colder

If your hands are being warmed by holding them above a flame, then the primary form of heat transfer is which process?

convection

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

crushed

When a volume of air is compressed, its temperature

decreases

When water freezes, the entropy of the water

decreases

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

density and pressure *the answer is both of these

What happens to water when heated from 0 degrees C to 4 degrees C?

density increases

What happens to water when its temperature is reduced from 12 degrees C to 4 degrees C?

density increases

The second law of thermodynamics leads us to conclude that

disorder in the universe is increasing with the passage of time

The work output of a perfectly constructed heat engine

equals the difference between its heat intake and heat exhaust

If a volume of air is warmed, it

expands

What happens to a given mass of water when cooled between 4C and 0C?

expands

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

faster

Energy transfer by convention is primarily restricted to

fluids

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

gives up additional energy when it condenses and has more energy per kilogram than boiling water *the answer is both of these

A good absorber of radiation is a

good emitter of radiation

When a vapor condenses

heat energy leaves the substance

+Q when

heat is added to the system

-Q when

heat is lost from the system

Food in a pressure cooker is cooked faster because of the

high temperature

An adiabatic process

involves no net heat entering or leaving a system

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

is a better insulator than tile

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

kinetic energy, but more speed

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

Double the absolute temperature of helium gas, and the molecules of helium, on average, speed up by

less than twice

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

looseness of outer electrons in metal atoms

Convection can occur

only in liquids and gases

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

By what primary heat transfer mechanism does the sum warm the earth?

radiation

If you hold your hand to one side of a flame, the predominant form of heat transfer that you will experience is

radiation

The planet Earth loses heat mainly by

radiation

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

radiation

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

raises the boiling point of water

When liquids change to a solid phase, they

release energy

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

releases energy

A refrigerator

removes thermal energy form inside the refrigerator

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 primary reason why a sandy beach gets so hot on a sunny day is because

sand has a small specific heat

A chunk of ice (T= -20C) is added to thermally insulated container of cold water (T= 0C). What happens in the container?

some of the water freezes and the chunk of ice gets larger

Sea breezes on a beach are attributed to a difference between land and water with respect to what property?

specific heat

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

stay the same

When heat is added to boiling water, the water temperate

stays the same

Which involves the larger number of calories?

the condensation of 1g of steam at 100C water

Evaporation is a cooling process because

the more energetic molecules are about to escape the liquid

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

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

Geothermal heating and cooling

uses the ground as a heat source or heat sink

The cooling effect inside a refrigerator is produced by

vaporizing the refrigerator liquid

Which one of the following statements is the best explanation for the fact that metal pipes that carry water often burst during cold winter months?

water expands upon freezing while the metal contracts at lower temperatures

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

wet

-W when

work is done by the system

+W when

work is done on the system