Gaseous molecular structure

In the gas state, the intermolecular forces between the particles are weak, so the particles are very far apart and move around randomly at high speeds. This allows gasses to take the shape and volume of their container.

Kinetic energy

All matter is made up of tiny particles that are in constant motion. Kinetic energy refers to the energy that the particles (atoms, ions, or molecules) have because they are moving.

Thermal energy

The temperature of matter is related to the average kinetic energy of its particles. When matter is heated, the particles gain energy and move faster, resulting in an increase in temperature.