2.3 Transfer of Energy as 2.3 Transfer of Energy as heat can be controlled.heat can be controlled.

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Energy moves as heat in three Energy moves as heat in three ways:ways:

Conduction Conduction Convection Convection RadiationRadiation

ConductionConduction The process that moves energy from one The process that moves energy from one

object to another when they are physically object to another when they are physically touching. touching. – Ex, metal spoon is in a cup of hot cocoa. Ex, metal spoon is in a cup of hot cocoa. – Ex, any physical contact with anything Ex, any physical contact with anything

(That’s Hot!)(That’s Hot!)

Controlling the Heat?Controlling the Heat?*Conductors*Conductors- - Materials that transfer energy Materials that transfer energy

easily easily Ex. -Iron or metal pots and pans Ex. -Iron or metal pots and pans

(The handles of pot and pans are plastic to stop the energy transfer) (The handles of pot and pans are plastic to stop the energy transfer)

InsulatorsInsulators-- are poor conductors (they do not are poor conductors (they do not transfer energy easily)transfer energy easily)

Controlling the Heat (continued)Controlling the Heat (continued)

InsulatorsInsulators-- are poor conductors (they do not are poor conductors (they do not transfer energy easily)transfer energy easily)

– Ex. wood, paper, Plastic foam, thermos, Ex. wood, paper, Plastic foam, thermos, Keeps drinks cold or hot.Keeps drinks cold or hot.

ConvectionConvection The process that The process that transfers energy by transfers energy by movement of particles movement of particles within a liquid or gas. within a liquid or gas.

– Process –> (When cooler – denser particles Process –> (When cooler – denser particles replace the warmer – less dense particles) replace the warmer – less dense particles)

Examples of ConvectionExamples of Convection

Examples: Examples: –Keeping houses warm Keeping houses warm

–Air outside in our atmosphere. Air outside in our atmosphere.

–Water molecules move to heat a pot Water molecules move to heat a pot of waterof water

RadiationRadiation The energy travel as Electromagnetic The energy travel as Electromagnetic

Waves such as: Visible light, Microwaves, Waves such as: Visible light, Microwaves, Infrared Light. Infrared Light.

All things emit radiation – release energy to All things emit radiation – release energy to their surroundings. (Even People!) their surroundings. (Even People!) – Major source of Electromagnetic Waves is the Major source of Electromagnetic Waves is the

sun sun – Things that absorb energy from the sun. Things that absorb energy from the sun.

Air, Concrete, Sidewalks..etcAir, Concrete, Sidewalks..etc

Polar bear’s skin/fur are very good insulators- Polar bears have several layers of insulation to keep

their body heat in.

Your Clothes do the same for you. Your body heat is trapped by the cloth. (keeping you nice and warm.)

Warmest clothes are better insulators. Ex. Wool

*Keeping cocoa hot in a Thermos - this is an insulatorA Thermos keeps liquid warm because it keep the energy from flowing

out of the container.

Heaters or fireplaces help keep your houses warm. Insulation within the walls of your house

help keep the energy inside the house.

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