section 2: transferring thermal energy chapter 6: thermal energy

Section 2:Transferring Thermal

EnergyChapter 6: Thermal Energy

WARM-UP: What does it mean to be a

good conductor?

What types of materials are the best conductors?

LEARNING GOALS Compare the transfer of heat

energy through conduction, convection, and radiation.

Compare and contrast conductors and insulators.

Explain how insulators are used to control the transfer of thermal energy.

TRANSFERRING THERMAL ENERGY There are 3 ways that

thermal energy is transferred from place to place: Conduction Convection Radiation

CONDUCTION

Conduction: transfer of thermal energy by collisions between particles in matter

Think of a metal spoon being heated by a flame.

CONDUCTION

Kinetic energy of the particles close to the flame increases.

Those particles collide with the particles close to them and thermal energy is transferred.

CONDUCTION

Conduction occurs when thermal energy is transferred from place to place without the transfer of matter!

HEAT CONDUCTORS

Heat moves fastest by conduction in solids.

HEAT CONDUCTORS

Heat moves a little slower by conduction in liquids.

HEAT CONDUCTORS Heat moves the slowest by

conduction in gases because the particles are so far apart.

HEAT CONDUCTORS

The best conductors of heat are metals because their electrons flow freely through the metal. Silver, copper, and aluminum

are among the best conductors of heat.

CONVECTION

Convection: transfer of thermal energy in a fluid (liquid or gas) by the movement of warmer and cooler fluid from place to place.

CONVECTION More energetic

particles collide with less energetic particles and transfer thermal energy.

More energetic particles move faster from place to place.

CONVECTION – THE LAVA LAMP Oil is cool and dense

and sits on the bottom of the lamp.

As it warms, the oil expands and becomes less dense than the surrounding fluid.

CONVECTION – THE LAVA LAMP The oil then rises

and loses heat to the surrounding fluid.

It becomes dense again and sinks.

RADIATION

Radiation: transfer of energy by electromagnetic waves Energy transferred by

radiation is called radiant energy.

RADIATION

When you stand near a fire to warm your hands, you are warming them using radiation.

INSULATORS

Insulator: material that slows down heat transfer

Gases are usually much better insulators than solids or liquids. Conduct heat poorly since

particles are far apart.

INSULATORS

Examples: fleece jacket and thermos

CHECK-IN: Would plastic foam (which

contains pockets of air) be a good insulator or good conductor? Explain why.