B.1 Thermal energy transfers but short summary

What can explained by considering the arrangement of particles

The macroscopic properties of solids, liquids and gases (e.g. hardness, rigidity) can be explained by considering the arrangement of particles.

Density

1. material property

2. describes the ratio of mass to volume

3. irrespective of a body's dimensions.

Internal energy

1. the sum of the kinetic and potential energies of particles in liquids and solids

2. the sum of the kinetic energies of particles in gases.

Temperature

1. a macroscopic property associated with whole bodies or containers

2. proportional to the mean kinetic energy of particles when measured in kelvin.

Kelvin scale

The Kelvin scale is a translation of the Celsius scale for temperature.

Specific heat capacity

Specific heat capacity is a measure of the thermal energy required to change the temperature of a unit mass of a material.

Specific latent heat

Specific latent heat is a measure of the thermal energy required to change the state of a unit mass of a body.

Thermal energy in a solid

Thermal energy flows in solids via conduction, at a rate affected by conductivity, cross-sectional area and temperature gradient (the variation in temperature with distance), until the mean kinetic energy of particles becomes evenly distributed.

Thermal energy in a fluid

Thermal energy is transferred in fluids by convection currents, with high temperature, low-density collections of particles rising, and low temperature, high-density collections of particles sinking and filling any low-pressure regions.

Emissivity

1. a measure of how effectively a body radiates heat.

2. It is measured from 0 to 1, with 1 being a perfect radiator and 0 being the opposite; a perfect reflector.

bodies that are hotter than absolute zero

All bodies that are hotter than absolute zero radiate thermal energy, with power (or luminosity) dependent on emissivity, cross-sectional area and absolute temperature, and with peak wavelength inversely proportional to absolute temperature.

Intensity (or brightness) of radiation

Intensity (or brightness) of radiation is inversely proportional to the square of the distance from the source.

What can knowledge of a body's brightness and distance away be used to determine?

Knowledge of a body's brightness and distance away can be used to determine its luminosity, which in turn can be used to determine its surface temperature and, hence, peak wavelength (or vice versa).