HEAT ENERGY(and the three ways it moves)

Tahoma Jr. High8th Grade ScienceMaple Valley, WA

WRONG HEAT

ConductionConduction is the transfer of heat by contact (touching).

The flame is in contact with the rod and the heat travels down the rod to your hand (particles in the rod start moving faster and bump into each other causing friction).

(look at the yellow = cool changing to red = hot)

Convection

Convection is the movement of heat through “fluids” (gases and liquids).

Fluids will rise when heated because hotter less dense particles “float” above more dense materials – then they cool off away from the heat source, become more dense, and fall down around the side because the hot stuff is rising below them.

Radiation

Radiation is the movement of heat without a medium/material (i.e. no particles to transfer the energy).

Energy from the Sun comes to us through space (which has “no” particles being a vacuum)by radiation (which simply means “spreading out from the source”).

images using infrared camera

How do you know the truck below has been stopped for a while?

Most transfers of heat involvemore than one method.

Summary•Heat flows from hot objects to cold objects (hot objects HAVE the energy to give away) •Heat flow rate depends on temperature difference (bigger difference causes faster travel)

•Heat is NOT temperature(it is energy, temperature measures particle movement)

•Heat moves by conduction, convection, or radiation

•Infrared energy is heat energy (spread by radiation)

QuickCheck For

Understanding…

Which one of the following statements about heat is correct ?

A  It moves from cold objects to hot objects.

B  It moves from hot objects to cold objects

C  The more the heat flows the lower the temperature.

D  Objects only radiate when they reach a temperature of at least 100 degrees Celsius

What do we call the process in which heat moves through a solid material ?

A  Conduction

B Convection

C Radiation

D  Insulation

Which one of these describes a solid material that blocks the flow of heat ?

A  Conduction

B  Convection

C  Radiation

D  Insulation

The Sun transfers its heat to the Earth by:

A  Conduction

B  Convection

C  Radiation

D  Insulation

A small crystal of potassium permanganate (purple dye) is placed

at the bottom of a beaker of water. The beaker is heated, and the purple dye is

seen to rise. This is due to:

A  Conduction

B  Convection

C  Radiation

D  Insulation

Heat radiation is called:

A  Ultraviolet

B  Ultrared

C  Infraviolet

D  Infrared

Speaking of heat – check out this map showing how much average temperatures have changed in each state since 1970

(the first Earth Day)

end show

YELLOW means little change – DARK RED is a LOT of change.

Luckily WA state is one of the few states that isn’t changing very fast – but that could change.