# Physics, Newtonian World and Astrophysics, Thermal Physics

Absolute Temperature

A scale for measuring temperature based on absolute zero and the triple point of pure water.

Absolute Zero

The lowest possible temperature, where particles have a minimum internal energy.

Avogadro Constant

The number of atoms in 12g of carbon-12.

Boltzmann Constant

A constant to relate the mean kinetic energy of the atoms in a gas to the gas temperature, calculated from the molar gas constant divided by the Avogadro Constant.

Boyle’s Law

The pressure of an ideal gas is inversely proportional to its volume, for a constant mass and temperature of gas.

Brownian Motion

The continuous random motion of small particles suspended in a fluid.

Celsius Scale

A temperature scale with 100 degrees between the freezing point and the boiling point of pure water.

Equation of State of an Ideal Gas

pV = nRT, where n is the number of moles of gas.

Gas Laws

The laws governing the behaviour of ideal gases.

Ideal Gas

A model of a gas including assumptions that simplify the behaviour of real gases.

Kelvin

The SI base unit of the absolute scale of temperature.

Kinetic Model

A model that describes all substances made of atoms, ions or molecules, arranged differently depending on the phase of the substance

Maxwell-Boltzmann Distribution

The distribution of the speeds of particles in a gas.

Mean Square Speed

The mean of the squared velocities of the particles in a gas.

Molar Gas Constant

The constant in the equation of state of an ideal gas.

Phase

The substance’s state of matter

Root Mean Square Speed

The square root of the mean square speed of all the particles in a gas.

Specific Heat Capacity

The energy required per unit mas to change the temperature by 1K.

Specific Latent Heat

The energy required to change the phase per unit mas while at a constant temperature.

Specific Latent Heat of Fusion

The energy required to change a unit mass of a substance from solid to liquid while at constant temperature.

Specific Latent Heat of Vaporisation

The energy required to change a unit mass of a substance from liquid to gas while at constant temperature.

Thermal Equilibrium

A state in which there is no net flow of thermal energy between the objects involved.

Triple Point

The temperature and pressure at which all the phases of a substance can exist in thermodynamic equilibrium.