Thermal Energy Transfer Unit 6: Thermal Energy

Review What is the difference between temperature and heat? Temperature is the measure of the average kinetic energy of the particles in an object Heat is the transfer of energy between object due to a difference in temperature

Review In what direction does heat ALWAYS flow? From areas of higher temperature to areas of lower temperature

Thermal Energy Transfer Thermal energy transfer will travel from objects or locations at higher temperature to objects or locations at lower temperature REMEMBER: during energy transfers, the law of conservation of energy is always observed Energy cannot be created or destroyed: only transformed

Thermal Energy Transfer Three types of thermal energy transfer: Conduction Convection Radiation

Conduction Conduction is the transfer of energy through matter by direct contact between particles Usually occurs between solids

Conduction For conduction to work, the materials must be: In direct contact with each other At different temperatures

Conduction Heat is transferred from one particle to the next as each particle vibrates more quickly

Convection Convection is the transfer of energy through the movement of matter Convection only occurs in FLUIDS (liquids or gases)

Radiation Radiation is energy transfer through electromagnetic waves that do not require matter (a medium) Examples: sunlight, space heater, microwave oven

Label the following diagram with the terms conduction, convection, and radiation

Conductors and Insulators Conductors are any material through which energy is easily transferred Examples: metals and waters

Conductors and Insulators Insulators slow down energy transfer and are poor conductors Examples: oven mitts, rubber, plastics, styrofoam

The Rate of Thermal Energy Transfer The rate at which thermal energy is absorbed or emitted depends on the object’s: Color Starting temperature Texture Exposed surface area

The Rate of Thermal Energy Transfer If all other conditions are kept equal, in a given amount of time, black rough surfaces absorb more thermal energy than smooth white surfaces

The Rate of Thermal Energy Transfer White surfaces reflect all colors of white light Black surfaces absorb all colors of white light It will make sense that, if the black surfaces are absorbing more light than the white surfaces, the black surfaces also absorb more heat