Heat Transfer& Phases

Heat Transfer& Phases

Intro Chapter Intro Chapter

• Is the ability to do work and cause a change.

• Can be transferred.– Gases and liquids are made of molecules that are

constantly moving (kinetic energy). The faster they are moving the more energy they have.

– Solids- molecules vibrate close together and transfer energy.

Energy

• The energy transferred from a hotter object to a cooler one.

• Three ways it is transferred.

Heat

• Is the total energy of motion in the molecules of a substance. • Gases are made of molecules that are

constantly moving. The faster they are moving the more energy they have.

Thermal Energy

• The average amount of energy of motion in the molecules of a substance.

• It is a measure of how hot or cold something is.

Temperature

Speed of Molecules & Temp

• What happens to the speed of the molecules when temperature is increased?

Speed of Molecules & Temp

• What happens to the speed of the molecules when temperature is increased?

Speed of Molecules & Temp

• What happens to the speed of the molecules when temperature is increased?

Speed of Molecules & Temp

• What happens to the speed of the molecules when temperature is increased?

Phase Changes

• When a substance changes from one state or phase to another.

• Solids

• Liquids

• Gases

• Always occur with a change in heat, which is energy.

Solids

• Have definite shape and volume

• Solid to liquid- melting

• Solid to gas- sublimation

Liquids

• Has a definite volume, and is able to take the shape of the container holding it.

• Liquid to solid- Freezing

• Liquid to gas- vaporization

• Boiling and Evaporation

Gases

• A state of matter without definite shape or volume.

• Phase Change-

• Gas to liquid- condensation.

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• The direct transfer of energy over long distances of empty space.

• Moves in waves. (Electromagnetic Waves)

• Can not see it, but feel it a heat (Infrared)– Sunlight– Open fire

ClimateRadiation

• Heat transfer by direct contact of particles of matter. (Transfer by Touching)

• Particles bump into each other and transfer their energy heating them up.– Putting your hand on a hot

stove.

Conduction

• Heat transfer by the circular movement of a fluid (liquids and gasses).

• Particles flow transferring heat energy.• Caused by differences in density.

Convection

• Density: the amount of mass in a given volume. D=M/V

• Heated Fluids:– Move faster and bump into other particles.– They spread out increasing the volume.– Density decreases

• Cooling Fluids– Move slower– They come together decreasing the volume.– Density increases

How Convection Works