Physics B.1 Thermal Energy Transfers

Molecular theory

Describes the behavior of matter in terms of the motion and interactions of its constituent particles.

Density

The mass per unit volume of a substance, given by ρ = m / V.

Temperature

A measure of the average kinetic energy of the particles in a substance, measured in degrees Celsius or Kelvin.

Internal energy

The total energy of a system due to the kinetic and potential energies of its particles.

Phase change

A transition of a substance from one state of matter to another at a constant temperature.

Specific heat capacity

The amount of heat energy required to raise the temperature of a unit mass of a substance by one degree.

Specific latent heat

The amount of heat energy required to change the phase of a unit mass of a substance without a temperature change.

Conduction

The transfer of thermal energy through a material without the movement of the material itself.

Convection

The transfer of thermal energy by the movement of a fluid due to differences in density.

Thermal radiation

The transfer of thermal energy by electromagnetic waves, which does not require a medium.

Stefan-Boltzmann law

States that the total energy radiated per unit area is proportional to the fourth power of the absolute temperature.

Apparent brightness

The amount of energy received per unit time per unit area from a light source.

Luminosity

The total amount of energy emitted per unit time by a light source, typically measured in watts.

Emission spectrum

The distribution of electromagnetic radiation emitted by an excited substance, providing information about its energy levels.

Wien’s displacement law

States that the peak wavelength of radiation from a black body is inversely proportional to its absolute temperature.