Solids, Liquids and Gases: Temperature and Particle Theory

Each substance can exist in three different states: solid, liquid, and gas.
The state of a substance at room temperature is determined by the forces between its particles.
Particles in a solid are closely packed in a regular pattern. They vibrate in fixed positions but do not move from place to place.
Solid substances have a fixed shape and cannot flow.
Particles in a liquid are in a random arrangement but are still close together.
They can move around each other, hence liquids can flow and take the shape of their container.
In gases, particles are far apart in a random arrangement. They move freely and have most energy among the three states of matter.
Gases fill any container they are put in, and can be easily compressed because of the large spaces between particles.
Temperature is a measure of the average kinetic energy of particles in a substance.
Increasing the temperature of a substance gives the particles more energy. This can cause a substance to change state: from solid to liquid (melting), liquid to gas (evaporating/boiling) or from solid straight to gas (sublimation).
Decreasing the temperature removes energy from the particles. This can make a substance change from gas to liquid (condensing) or from liquid to solid (freezing).
The greater the temperature, the greater the kinetic energy of the particles and the faster they move.
The Kelvin (K) is the SI unit for temperature, where 0K (absolute zero) is the point at which particles have minimum (but not zero) kinetic energy.
A substance can stay at the same temperature despite energy being added when it is changing state (melting, boiling) because the energy is being used to break bonds between the particles.
In every change of state, there is no change in the mass of a substance.
This particle theory helps explain the different states of matter, and how substances change state with changes in temperature.