Heat Energy Transfer SNC2D. The Transfer of Heat Energy There are 3 different mechanisms by which heat energy may be transferred:

Heat Energy TransferHeat Energy Transfer

SNC2DSNC2D

The Transfer of Heat EnergyThe Transfer of Heat Energy

There are 3 different mechanisms by There are 3 different mechanisms by which heat energy may be which heat energy may be transferred:transferred:



• radiationradiation




• conductionconduction




• conductionconduction

• convectionconvection

RadiationRadiation

Radiation is the release of infrared Radiation is the release of infrared radiation by a substance at a higher radiation by a substance at a higher temperature than its surroundings.temperature than its surroundings.

RadiationRadiation

Radiation is the release of infrared Radiation is the release of infrared radiation by a substance at a higher radiation by a substance at a higher temperature than its surroundings.temperature than its surroundings.

This is the only mechanism that works in This is the only mechanism that works in a vacuum (outer space, including the a vacuum (outer space, including the space between the Earth and the Sun).space between the Earth and the Sun).

ConductionConduction

Conduction is the transfer of kinetic Conduction is the transfer of kinetic energy (the energy of motion) energy (the energy of motion) between particles in direct contact.between particles in direct contact.

ConductionConduction

Conduction is the transfer of kinetic Conduction is the transfer of kinetic energy (the energy of motion) energy (the energy of motion) between particles in direct contact.between particles in direct contact.

Conduction is therefore most effective Conduction is therefore most effective in solids.in solids.

ConvectionConvection

Convection is the movement of particles Convection is the movement of particles from one location to another: cooler, from one location to another: cooler, denser material will sink relative to denser material will sink relative to warmer, less dense material.warmer, less dense material.

Convection is therefore most effective in Convection is therefore most effective in liquids and gases.liquids and gases.

Solar RadiationSolar Radiation

So energy arrives from the Sun in the So energy arrives from the Sun in the form of radiation (both visible and form of radiation (both visible and infrared). infrared).

However, not all of this energy is However, not all of this energy is absorbed. Some is reflected. The absorbed. Some is reflected. The percentage of radiation reflected is the percentage of radiation reflected is the albedoalbedo of the surface. Ice and snow of the surface. Ice and snow reflect sunlight more than land or reflect sunlight more than land or ocean.ocean.



Different surfaces also have different Different surfaces also have different temperature responses to the same temperature responses to the same heat energy input.heat energy input.


Different surfaces also have different Different surfaces also have different temperature responses to the same temperature responses to the same heat energy input. heat energy input.

E.g. water has a high E.g. water has a high heat capacityheat capacity, , which means that it takes more energy which means that it takes more energy to heat the oceans than the land (which to heat the oceans than the land (which is why the water at the beach on a is why the water at the beach on a summer’s day is colder than the sand).summer’s day is colder than the sand).


Also, arriving solar radiation is not Also, arriving solar radiation is not distributed evenly: the equatorial distributed evenly: the equatorial regions receive, on average, more regions receive, on average, more direct sunlight than the polar direct sunlight than the polar regions.regions.

Heat Transfer on EarthHeat Transfer on Earth

All this uneven heating of the Earth’s All this uneven heating of the Earth’s surface results in the transfer of heat surface results in the transfer of heat energy (primarily from the equatorial energy (primarily from the equatorial region to the poles) by convection in region to the poles) by convection in the Earth’s atmosphere and the Earth’s atmosphere and hydrosphere.hydrosphere.

Convection in the Convection in the AtmosphereAtmosphereThe warm, moist air at the Equator rises and The warm, moist air at the Equator rises and

releases its moisture (resulting in releases its moisture (resulting in rainforest biomes) and cools, sinking down rainforest biomes) and cools, sinking down at about 30at about 30oo North and 30 North and 30oo South latitude South latitude (resulting in desert biomes).(resulting in desert biomes).

Convection in the Convection in the AtmosphereAtmosphereBecause the Earth is rotating, the Coriolis Because the Earth is rotating, the Coriolis

Effect forces the surface air moving toward Effect forces the surface air moving toward the Equator from east to west, resulting in the Equator from east to west, resulting in the NE and SE trade winds.the NE and SE trade winds.

Convection in the Convection in the AtmosphereAtmosphereSimilar convection cells between 30Similar convection cells between 30ooN and N and

6060ooN and 30N and 30ooS and 60S and 60ooS latitudes result in S latitudes result in prevailing westerly winds (which is why prevailing westerly winds (which is why the weather across Canada moves from the weather across Canada moves from west to east). west to east).

Convection in the Convection in the HydrosphereHydrosphereThe patterns of ocean currents are The patterns of ocean currents are

complicated by the position of the complicated by the position of the continents.continents.

The Effects of Climate The Effects of Climate ChangeChange

It is important to understand how heat It is important to understand how heat energy transfer affects the climate to energy transfer affects the climate to understand how global warming can understand how global warming can change climate.change climate.

The Effects of Climate The Effects of Climate ChangeChangeE.g. global warming has resulted in E.g. global warming has resulted in

increased evaporation from the oceans, increased evaporation from the oceans, resulting in increased precipitation of snow resulting in increased precipitation of snow over the Northern Hemisphere (Siberia in over the Northern Hemisphere (Siberia in particular), resulting in increased albedo, particular), resulting in increased albedo, resulting in colder winters.resulting in colder winters.

The Effects of Climate The Effects of Climate ChangeChange

E.g. the increased melting of glaciers E.g. the increased melting of glaciers and Arctic ice could result in and Arctic ice could result in increased cold ocean currents from increased cold ocean currents from the Arctic, possibly reversing the the Arctic, possibly reversing the North Atlantic Drift that keeps North Atlantic Drift that keeps Europe temperate.Europe temperate.

More PracticeMore Practice

p. 289 # 6, 7, 8, 12, 13 p. 292 #7, 16p. 289 # 6, 7, 8, 12, 13 p. 292 #7, 16

Heat Energy Transfer SNC2D. The Transfer of Heat Energy There are 3 different mechanisms by which heat energy may be transferred:

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