P2 - Ch19-20 - Thermal Physics and gases

Internal energy

The internal energy of an object is the sum of the random distribution of the kinetic and potential energies of its molecules.

First law of thermodynamics

The change of internal energy of an object = the total energy transfer due to work done and heating.

Thermal equilibrium

If there is no overall energy transfer between two objects, those objects are in thermal equilibrium.

Absolute zero

0 K. The lowest possible temperature.

Absolute scale of temperature

The temperature scale in Kelvin. Based on absolute zero and the triple point of water.

Specific heat capacity

The energy required to increase the temperature of 1 kg of a substance by 1 K, without change of state.

Specific latent heat of fusion

The energy required to change the state of 1kg of a substance from solid to liquid, without change in temperature.

Specific latent heat of vaporisation

The energy required to change the state of 1kg of a substance from liquid to vapour, without change in temperature.

Gas pressure

The force per unit area that a gas exerts normally on a surface.

Boyle's Law

For a fixed mass of gas at constant temperature, pV = constant (where p = gas pressure and V = gas volume).

Charles' Law

For a fixed mass of gas at constant pressure, V/T = constant (where V = gas volume and T = temperature measured in Kelvin).

Pressure Law

For a fixed mass of gas at constant volume, p/T = constant (where p = gas pressure and T = temperature measured in Kelvin).

Ideal gas Law

pV/T = constant. An ideal gas obeys Boyle's Law. This law becomes pV = nRT, the ideal gas equation.

Avogadro's number / constant, NA

The number of atoms in exactly 12 g of the carbon-12 isotope.

The mole

One mole of a substance is the quantity of that substance that contains NA particles.

The molar mass

The mass of 1 mol of a substance.