Thermal Energy Transfer

Thermal Energy Transfer

6th grade scienceReese

Temperature• Temperature measures the average kinetic

energy of the particles in a substance. The more KE the higher the temperature.

• How HOT or COLD an object is.

Heat Transfer and Fact

• Heat is the transfer of thermal energy between substances at different temperatures.

• When objects are heated, their particles move faster and take up more space so they EXPAND. When heat is released from object, the particles slow down they CONTRACT.

Important Temperatures

• 0 C = 32 F (Freezing Water)• 100 C = 212 F (Boiling Water)• 37 C = 98.6 F (Body Temperature)

Temperature Scales

HEAT FLOW: HEAT ALWAYS FLOWS FROM WARMER TO COOLER

UNTIL THERMAL EQUILIBRIUM IS REACHED!

Heat Flow

Human bodies work differently. We do not reach equilibrium with our environmentbecause our bodies help regulate temperature. We canfeel temperature changes though…

Conduction• Conduction is the transfer of heat through

materials by the direct contact of matter.• Dense metals like copper and aluminum are

very good thermal conductors. Solids usually are better heat conductors than liquids, and liquids are better conductors than gases.

Conduction Example

Conduction Example

Thermal Insulator

• A thermal insulator is a material that conducts heat poorly.

• Heat flows very slowly through the plastic so that the temperature of your hand does not rise very much.

Thermal Conduction

Thermal Conduction

Why does metal feel colder than wood, if they are both at the same temperature?

Metal is a conductor, wood is an insulator. Metal conducts the heat away from your hands. Wood does not conduct the heat away from your hands as well as the metal, so the wood feels warmer than the metal.

Convection

• Convection is the transfer of heat by the motion of liquids and gases (FLUIDS).– Convection in a gas occurs because gas expands

when heated and contract when cooled.– Convection occurs because currents flow when

hot gas rises and cool gas sink.– Convection in liquids also occurs because of

differences in density.

Water movement

Hot water rises

Cooler water sinks

Convection current

Cools at the surface

Weather

• When hot air rises, the air is replaced by the surrounding cooler, more dense air, which we feel as wind. Convection currents are responsible for weather patterns in the troposphere.

Sea Breezes

Earth’s climate due to convection

Cold air sinks

Where is the freezer

compartment put in a fridge?

Freezer compartmen

t

It is put at the top, because cool air sinks, so it cools the food on the way down.

It is warmer at the

bottom, so this warmer

air rises and a

convection current is

set up.

Radiation

• Radiation is the transfer of heat through electromagnetic waves. Radiation DOES NOT require matter in order to transfer thermal energy!

There are no particles between the Sun and the Earth so thermal energy CANNOT travel by conduction or by convection. ONLY....

?RADIATION

RadiationMain source of Earth’s radiation

RadiationShiny objects or light colored objects do not absorb radiation as well as dull black objects.