Heat Heat TransferTransfer

Three Methods of Heat Three Methods of Heat TransferTransfer Heat always goes from hot to cold.Heat always goes from hot to cold. Heat is movement of energy from a Heat is movement of energy from a

warmer object to a cooler object.warmer object to a cooler object.

Radiation Radiation Heat transfer by radiation takes place with no Heat transfer by radiation takes place with no

direct contact between a heat source of an direct contact between a heat source of an object.object.

Will transfer through the vacuum of space. Will transfer through the vacuum of space. Matter is not required.Matter is not required.

Other familiar forms of radiation include the heat Other familiar forms of radiation include the heat you feel around a flame or open fire. Radiation you feel around a flame or open fire. Radiation enables sunlight to warm Earth’s surface.enables sunlight to warm Earth’s surface.

                                              

              

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ConductionConduction What happens as a spoon What happens as a spoon

heats up in a pot of soup?heats up in a pot of soup? The heat is transported from The heat is transported from

the hot soup and the pot to the hot soup and the pot to the particles in the spoon. the particles in the spoon.

The particles near the bottom The particles near the bottom of the spoon vibrates faster of the spoon vibrates faster as they are heated, so they as they are heated, so they bump into other particles as bump into other particles as they travel through the they travel through the handle of the spoon and pot.handle of the spoon and pot.

Soon the handle will be too Soon the handle will be too hot to hold!hot to hold!

Usually associated with Usually associated with solids.solids.

ConvectionConvection Conduction heats up the spoon, but how does the soup inside Conduction heats up the spoon, but how does the soup inside

the pot heat up? Heat transfer involving the movement of the pot heat up? Heat transfer involving the movement of fluids- liquids and gases-fluids- liquids and gases- it is called convection. it is called convection.

During convection, heat particles of fluids begin to flow During convection, heat particles of fluids begin to flow transferring heat energy from one part of the fluid to transferring heat energy from one part of the fluid to another.another.

Convection and Convection and DensityDensity

The warmer particles The warmer particles are moving faster, are moving faster, they spread out more.they spread out more.

So they are less dense So they are less dense and rise.and rise.

After giving their After giving their energy to the cooler energy to the cooler fluid at the top, they fluid at the top, they are now cooler and are now cooler and more dense. More more dense. More dense fluids sink.dense fluids sink.

Convection Currents Convection Currents DiagramDiagram

Convection CurrentsConvection Currents The heating and cooling of the fluid, The heating and cooling of the fluid,

changes in the fluid’s density, and the changes in the fluid’s density, and the force of gravity combine to place the force of gravity combine to place the currents in motion. currents in motion.

Convection currents continue as long as Convection currents continue as long as heat is added without heat the currents will heat is added without heat the currents will stop when all of the material has reached stop when all of the material has reached the same temperature. However, heat from the same temperature. However, heat from the Earth’s mantle and core causes the the Earth’s mantle and core causes the currents to form in the asthenosphere.currents to form in the asthenosphere.

Key Terms!Key Terms!

Heat Transfer-Heat Transfer- The movement of energy from a The movement of energy from a warmer object to a cooler object.warmer object to a cooler object.

Radiation-Radiation- The direct transfer of energy through The direct transfer of energy through empty space by electromagnetic waves. empty space by electromagnetic waves.

Conduction-Conduction- The transfer of heat from one The transfer of heat from one substance to another by direct contact of particles substance to another by direct contact of particles of matter. of matter.

Convection-Convection- The transfer of heat by movements The transfer of heat by movements of a fluid.of a fluid.

Density- Density- The amount in a given space; mass per The amount in a given space; mass per unit volume.unit volume.

Convection Currents-Convection Currents- The movement of a fluid, The movement of a fluid, caused by differences in temperature, that caused by differences in temperature, that transfers heat from one part of the fluid to another.transfers heat from one part of the fluid to another.