What’s the difference???What’s the difference???Heat is energyHeat is energy that is transferredthat is transferred from from one object to another due to differences one object to another due to differences in temperature (in temperature (hot hot cold cold))

Temperature is a measureTemperature is a measure ofof the the molecular motion (molecular motion (kinetic energykinetic energy) of a ) of a substance (substance (more heat = more motionmore heat = more motion))

Lower Temperature = Higher Temperature =

Lower Kinetic Energy Higher Kinetic Energy

(less motion) (more motion)

--the transfer of heat through matter by the transfer of heat through matter by direct contactdirect contact

Heat moves from Heat moves from hot to coldhot to cold

Air is a very poor conductor of heat, so Air is a very poor conductor of heat, so conduction only involves the layer of air that is in conduction only involves the layer of air that is in direct contactdirect contact with Earth’s surface. with Earth’s surface.

Thermal Conductivities ( # = better conductor)Thermal Conductivities ( # = better conductor)

Water Water .60 .60 Diamond Diamond 24502450

Air Air .026.026 SilverSilver 420420

Aluminum Aluminum 240 240 ConcreteConcrete 1.11.1

IronIron 79 79 GlassGlass .80.80

Place a wooden spoon and a metal Place a wooden spoon and a metal spoon in the freezer.  Whichspoon in the freezer.  Whichwill cool faster?  After several hours, will cool faster?  After several hours, what would they feel like? what would they feel like?

--the transfer of heat by the transfer of heat by circulationcirculation within within a substancea substance

Heated air rises, cools, thenHeated air rises, cools, then

falls.  Air near heater isfalls.  Air near heater isreplaced by cooler air, andreplaced by cooler air, and

the cycle repeats.the cycle repeats.

Why are cooling Why are cooling coils in refrigerators coils in refrigerators placed at the top of placed at the top of the unit?the unit?

What if they were What if they were placed at the placed at the bottom?bottom?

When boiling When boiling water hot water water hot water

rises, cools,rises, cools,and falls.and falls.

Convection explains Convection explains the movement of the movement of materials throughout materials throughout the the lava lamplava lamp

Hot room air is forced outside, while cooler air replaces it.

--the transfer of energy (heat) through the transfer of energy (heat) through space by space by electromagnetic waveselectromagnetic waves

Electromagnetic Spectrum – all the types of radiation Electromagnetic Spectrum – all the types of radiation emitted from the sun.emitted from the sun.

Visible lightVisible light

ROYGBIVROYGBIV

Range of Range of wavelengths wavelengths visible to visible to humanshumans

What What happens happens when solar when solar radiation radiation strikes an strikes an object?object?

ConductionConduction Even in solid matter, like hot pots and cold feet, the atoms and

molecules are always doing a dance, jiggling up and down and all around. We can’t see them jiggle, but we can feel their energy. How? As heat!

Adding heat energy to matter makes its atoms and molecules jiggle even faster. As they speed up, they bump against their neighbors, and get them jiggling faster too.

Put a cool pan on a hot stove, and soon the pan is hot. If the handle is metal, it will get hot too, as the faster-moving molecules in the metal pass their energy along.

That’s conduction: Matter “conducting” energy throughout itself, through molecules bumping into each other.

ConvectionConvection

    Like conduction, convection happens in matter too, but only in liquids and gases—like water and air. The atoms and molecules in liquids and gases are farther apart than in solids. Because they have more room between them, they are freer to move around. As they heat up and jiggle faster, they move much farther, carrying the heat energy with them.

The atoms and molecules themselves move in currents. For example, a candle flame (which is made of gases so hot they glow) heats the air right around it. The warmed air rises, making a current. Cooler air moves in to replace the warmed air, gets warmed up too, and rises into the current.

RadiationRadiation

Radiation moves energy without any help from matter.

We say the Sun’s energy radiates through space to reach Earth. That means it travels in waves and doesn’t need atoms and molecules to move along. Energy that travels by radiation is called electromagnetic radiation. Light is one kind of electromagnetic radiation we can see. But light is just one tiny part of all the kinds of electromagnetic radiation.

Although we can’t see it, the heat we feel on our skin when we stand in the Sun or put our hands over a hot stove is caused by infrared.