Physics Chapter 22

Define convection.

A means of heat transfer by movement of the heated substance itself, such as by currents in a fluid.

How does an object's emission rate compare with its absorption rate?

Good emitters of radiant energy are also good absorbers; poor emitters are poor absorbers.

Good emitters of radiant energy are also good ___.

absorbers

An object in thermal equilibrium is both ___ and ___ energy at the same rate.

absorbing and radiating

What in an insulator?

any material that is a poor conductor of heat and that delays the transfer of heat

When a molecule collides with a molecule that is receding, its rebound speed after the collision is ___ than it was before the collision.

less

Objects of everyday temperatures emit waves mostly in the ___ end of the infrared region.

long-wavelength

Do objects at low temperatures emit waves with a longer or shorter wavelength than objects with higher temperatures?

longer

T/F: An insulator cannot totally prevent heat from getting through, but instead just reduces the rate at which heat penetrates.

true

T/F: As air rises and expands, it collides with more molecules that are receding than are approaching.

true

T/F: Conduction occurs without any overall transfer of matter.

true

T/F: Light-colored objects reflect more light than dark-colored ones.

true

T/F: Newton's law of cooling also holds for heating.

true

Convection currents stirring the atmosphere produce ___.

winds

Order the different types of radiant energy from the longest to shortest wavelength. gamma rays infrared radiation microwaves radio waves ultraviolet radiation visible light X-rays

1. radio waves 2. microwaves 3. infrared radiation 4. visible light 5. ultraviolet radiation 6. X-rays 7. gamma rays

What is a conductor?

A conductor is a material that conducts heat well.

Define insulator.

A material that is a poor conductor of heat and that delays the transfer of heat.

What substances emit radiant energy?

All substances continuously emit radiant energy in a mixture of wavelengths.

Define radiant energy.

Any energy, including heat, light, and X-rays, that is transmitted by radiation. It occurs in the form of electromagnetic waves.

___ is the gas most rapidly increasing in the atmosphere.

CO2

Why can't energy move from the sun to Earth by conduction or convection?

Conduction is the transfer of heat from molecule to molecule, and convection is the transfer of heat by expansion and rising of matter. Both of these are impossible in space because there is almost no matter.

Use the figure above to describe the Earth's global warming.

Earth's atmosphere allows short waves from the sun to pass through. These waves strike Earth, which re-radiates the energy as longer waves. Atmospheric gases absorb and re-emit much of this long-wavelength radiation back to Earth.

Define radiation.

Energy transmitted by electromagnetic waves.

How does conduction transfer heat?

In conduction, collisions between particles transfer thermal energy, without any overall transfer of matter.

How does convection transfer heat?

In convection, heat is transferred by movement of the hotter substance from one place to another.

Define conduction.

In heat, energy transfer from particle to particle within certain materials, or from one material to another when the two are in direct contact.

How does radiation transmit heat?

In radiation, heat is transmitted in the form of radiant energy, or electromagnetic waves.

You notice that a blacktop pavement becomes hotter than other nearby surfaces on a hot day. What will you notice about the temperature of the blacktop pavement at night?

It will cool faster than other surfaces.

Define conductors.

Material through which heat can be transferred.

Imagine stepping with one bare foot onto metal and with the other bare foot onto wood. Explain why the metal feels cool and the wood feels warm, even though they have the same temperature.

Metal is a good conductor, but wood is a poor conductor. Heat easily moves out of your foot into the cooler metal. Little heat moves out of your foot into the wood, so your foot does not sense that it is touching something cooler.

___ are the best conductors.

Metals

Define terrestrial radiation.

Radiant energy emitted from Earth.

Define greenhouse effect.

The warming effect whose cause is that short-wavelength radiant energy from the sun can enter the atmosphere and be absorbed by Earth more easily than long-wavelength energy from Earth can leave.

Explain why the inside of a car becomes so much hotter than its surrounding on a hot day.

Short wavelengths from the sun can pass through the car's glass and into the car, warming the car. The car radiates longer wavelengths that cannot pass out through the glass. The energy is trapped inside the car.

Explain why snow is sometimes used to construct dwellings in cold climates.

Snowflakes imprison a lot of air in their crystals and are good insulators. The snow prevents heat from escaping too rapidly.

What causes an object to cool faster?

The colder an object's surroundings, the faster the object will cool.

Suppose a heater is placed near the floor of a room. Describe the steps in which convection currents keep the air stirred up in the room.

The heater warms nearby air, and this warm air rises. Cooler air near the ceiling moves downward, and the heater warms it. This air then rises, and the process continues.

The figure above shows ice at the bottom of a test tube and boiling water at the top. Explain why the heat that boils the water doesn't melt the ice.

The hot water at the top of the tube is less dense and floats. Any heat that reaches the ice must be transferred by conduction, but water is a poor conductor of heat.

How does human activity affect climate change?

The near unanimous view of climate scientists is that human activity is a main driver of global warming and climate change.

Define stellar radiation.

The radiant energy emitted by the stars.

Define Newton's law of cooling.

The rate of cooling of an object - whether by conduction, convection, or radiation - is approximately proportional to the temperature difference between the object and its surroundings.

State Newton's law of cooling.

The rate of cooling of an object is approximately proportional to the temperature difference between the object and its surroundings.

Explain the two ways convection currents produced by uneven heating of Earth's surface produce sea breezes at night.

The shore cools off more quickly than the water. Air over the water rises, and cooler air from above the shore takes it s place, producing a breeze toward the sea.

Explain the two ways convection currents produced by uneven heating of Earth's surface produce sea breezes during the day.

The shore warms more easily than the water. Air over the shore rises, and cooler air from above the water takes its place, producing a breeze toward the land.

___ is the main greenhouse gas.

Water vapor

On a sunny day, Earth's surface is a net ___, and at night it is a net ___.

absorber; emitter

How do birds vary their insulation?

by fluffing their feathers to create air spaces

Suppose you have a box, painted white inside, which is closed except for a hole 2 centimeters wide. Which below explains why the hole appears black? a) The white paint inside the box absorbs almost all of the radiant energy that strikes it. b) The hole in the box is much to small to allow wavelengths of light to pass through. c) Light that enters is reflected and partly absorbed so many times that little is left to come out. d) The light that enters leaks out through the walls of the box.

c) Light that enters is reflected and partly absorbed so many times that little is left to come out.

Air is transparent to both infrared (long) waves and visible (short) waves, unless the air contains excess ___ and ___.

carbon dioxide and water vapor

Record-breaking cold nights occur when the skies are ___.

clear

In conduction, ___ between particles transfer thermal energy.

collisions

Is the following a conductor or insulator? aluminum

conductor

Is the following a conductor or insulator? copper

conductor

Is the following a conductor or insulator? iron

conductor

Is the following a conductor or insulator? silver

conductor

An object hotter than its surrounding eventually ___ to match the surrounding temperature.

cools

A good absorber of radiant energy appears ___.

dark

In expanding air, the average speed of the molecules ___, and the air cools.

decreases

Radiation is energy transmitted by ___.

electromagnetic waves

Definition of radiant energy.

energy that is transmitted by radiation

T/F: All substances continuously emit only one specific wavelength of radiant energy.

false

T/F: As air rises, it expands because more atmospheric pressure squeezes on it at higher altitudes.

false

T/F: Materials that are good conductors of heat are usually poor conductors of electricity.

false

T/F: both heat and cold are forms of energy.

false

The average ___ of radiant energy is directly proportional to the kelvin temperature of the emitter.

frequency

What is the big idea for Chapter 22: Heat Transfer?

heat can be transferred by conduction, by convection, and by radiation

In convection, heat is transferred by movement of the ___ substance from one place to another.

hotter

Which type of radiant energy you feel as heat if you sit near a fireplace? infrared radiation ultraviolet radiation microwaves X-rays

infrared radiation

Is the following a conductor or insulator? air

insulator

Is the following a conductor or insulator? cork

insulator

Is the following a conductor or insulator? paper

insulator

Is the following a conductor or insulator? polystyrene

insulator

Is the following a conductor or insulator? straw

insulator

Is the following a conductor or insulator? wood

insulator

Is the following a conductor or insulator? wool

insulator

The part of radiant energy that is absorbed by objects increases the ___ energy of the objects.

internal

Order the star colors white, red, and blue from coolest to hottest.

red, white, blue

The radiant energy emitted by stars is called___.

stellar radiation

An infrared thermometer measures the infrared radiant energy emitted by a body and converts it so ___.

temperature

The ___ of an object doesn't change if it is in thermal equilibrium.

temperature

The radiant energy emitted by Earth is called ___.

terrestrial radiation

A hot apple pie will cool faster in a freezer than on a kitchen table because ___.

the temperature difference is greater

Define conduction.

the transfer of energy within materials and between different materials that are in direct contact

What is the greenhouse effect?

the warming of a plant's surface due to the trapping of radiation by the plant's atmosphere

Glass is ___ to visible light waves, but ___ infrared waves.

transparent; absorbs