Solids, Liquids & Gases (OCR GCSE Physics A (Gateway)): Revision Note

Solids, Liquids & Gases

Solids & Liquids

• In solids and liquids, the molecules are tightly packed together

  • The difference is, in a liquid, the molecules have enough energy to push past each other

• As a result of this, the density of solids and liquids are roughly the same

The molecules in solids and liquids are tightly packed, giving them a high density

Gases

• In a gas, the molecules are widely separated

  • As a result of this, gases have significantly lower densities than solids or liquids

• At room temperature, the distance between molecules in a gas is roughly ten times (in each direction) the distance between molecules in a solid or liquid

• As a result, the density of a gas is typically around one-thousandth (1/1000) of the density of a solid or liquid, for example:

  • The density of water is 1000 kg/m³

  • The density of air at sea level and room temperature is 1.3 kg/m³

The molecules in a gas are widely spaced, giving it a much lower density