• All things are made up of molecules
• When things get heated, they absorb heat energy
• With more energy, molecules are able to move faster
• When molecules move faster, the temperature rises

What is Thermal Energy

• Thermal Energy is energy resulting from the motion of particles
• It is a form of kinetic energy and is transferred as heat
• Thermal Energy Transfer can occur by three methods:
• Conduction
• Convection
• Radiation

Conduction

• Conduction is the transfer of thermal energy through direct contact between particles of a substance, without moving the particles to a new location
• Usually occurs in solids
• When heat is supplied to one end, molecules at that end start to move more quickly
• In the process, they bump into their neighbors, transferring the kinetic energy

Convection

• Convection is the transfer of thermal energy through the movement of particles from one location to another
• Usually occur in fluids (liquids and gases)
• Example with boiling water:
• Water at bottom of the pan is heated first
• Heated water expands and density decreases
• Heated water begins to rise
• Cooler water with higher density from the sides of the pan rush down to take its place
• The cooler water gets heated and the cycle repeats
• We call these Convection Currents

Radiation

• Radiation is the emission of energy as waves or particles or rays
• Radiation does not require a medium to transfer energy
• Radiant energy is either reflected or absorbed by matter
• The energy that is absorbed increases the kinetic energy of the object
• This increases the temperature of the object
• Example … frying pan on a stovetop
• Energy is radiated from the heat source and absorbed by the lower surface of the pan
• For example… the sun
• Sun radiates energy in form of solar radiation
• When this energy reaches Earth, it is absorbed by matter (air, water, land)
• Absorbed radiant energy increases the kinetic energy of the matter, raising its temperature
• The sun is an emitter
• It gives out heat

• The Earth is an absorber
• It takes in the heat

Factors Affecting Radiation

ALBEDO

• Colour of the surface
• Albedo is the percentage of the incoming solar radiation that it reflects
• The albedo of Earth is about 30%
• Light-colored, shiny objects reflect more solar radiation and have a high albedo (ice, snow, sand)
• Darker, dull objects absorb more solar radiation and have a low albedo (forests, soils)
• Factors Affecting Radiation
• Surface Temperature
• The higher the surface temperature, the higher the rate of transfer

Surface Area

• The larger the surface area, the higher the rate of transfer
• Thermal Energy Transfer in the Atmosphere
• Things to Know:
  • Atmospheric Pressure > the pressure exerted by the mass of air above any point on Earth’s surface
  • Warm air is less dense than cold air
  • Warmer regions generally have less atmospheric pressure than colder regions
  • Wind > the movement of air from areas of high pressure to areas of low pressure
  • The rising and sinking masses of air in convection currents cause changes in atmospheric pressure … causing wind

Wind Patterns and Coriolis Effect

• Moves from WEST to EAST
• Closer to the equator in colder months
• Closer to Poles in warmer months
• Thermal Energy Transfer in the Hydrosphere
• The effect of water on the transfer of heat is significant
• Earth’s climate is affected by phase changes in the water cycle

Water Cycle

• Water molecules undergo changes of state (e.g. solid to liquid)
• When these changes occur, thermal energy is either released or absorbed
• Released from liquid > solid
• Absorbed from Liquid > gas
• Temp. remains the same between phase changes
• Through changes of state is how thermal energy is transferred through the biosphere

Ocean Currents

• Main pathways to transfer thermal energy from warmer regions to cooler regions
• Global winds push the water, driving the surface currents of the ocean
• The pattern of ocean currents is modified by the Coriolis Effect
• Currents in North veer to the right
• Currents in South veer to the left
• Thermal energy is also transferred vertically via convection currents
• (same principles as with air)