thermal energy & heat transfer

Thermal Energy & Heat TransferAdvanced Physical ScienceLockwood

Kinetic Energy

•Energy of Motion•KE = ½ m* V2

•When you were acting as a particle…the more you jumped around…the more KE you had

•All matter contains particles that are moving all the time

•Absolute zero=when matter stops moving (never been reached)

Temperature

•Temperature is the measure of the average kinetic energy of the particles in an object.

•The gas particles on the right have a higher KE than those on the left (therefore higher temperature)

Temperature (con’t)

Temperature does not depend on how much substance you have

The contents of the teapot and the coffee cup are at the same temperature

Thermal Energy•The TOTAL KE of all the particles that

make up the object•The higher the temperature, the higher

the thermal energy•The more substance present, the greater

the thermal energy (there is more thermal energy in the pan of soup than the bowl)

Heat•The energy transferred between objects that

are at different temperatures (diff Ave KE).

•Energy is transferred from faster (warmer) molecules to slower (cooler) molecules▫Occurs through collisions between molecules

•HEAT MOVES!! (not cold)•Heat is what causes something to FEEL hot

or cold▫Ex: A doctor’s stethoscope on your back…your

body heat is moving to the stethoscope.

Heat Transfer-3 types

•Conduction•Convection•Radiation

Heat Transfer - Conduction•Conduction- transfer of energy through matter

by the direct contact of particles •When objects that have different temperatures

come into contact, energy passes from warmer to cooler object until both have same temperature.▫Occurs because particles are in constant motion▫KE transferred as particles collide

Heat Transfer – Conduction (cont)• Conduction can also occur within an object such

as the spoon (below). The part of the spoon in the soup is hotter than the edge.

• Conduction works best in solids- especially metals- because particles are close together

• Metals- good conductors-because electrons move easily & transfer KE to nearby particles

Heat Transfer - Convection•Convection- transfer of thermal energy by

the movement (or circulation) of a fluid•Fluid- any material that flows (can be

liquid or gas)•Convection currents transfer heat from

warmer to cooler parts of a fluid.

Conduction and Convection

•Convection vs. Conduction- ▫Conduction involves collisions and

transfers of energy. ▫Convection involves movement of the

energetic particles from one location to another

•Conduction and convection can occur only when matter is present.

Heat Transfer - Radiation

•Radiation is heat transfer through space as electromagnetic waves.

•Does not require a medium.

Heat Transfer-summary of all types•Conduction, Convection, and Radiation

can occur in the same situation