The states of matter

Once they have been manufactured by the stars, atoms are virtually eternal. They can however be associated in different ways to form molecules which organise differently according to the environmental temperature and pressure. Atoms of oxygen (O) and hydrogen (H) have therefore existed for billions of years. However, molecules of water (H₂0) can easily be broken down into hydrogen and oxygen.

Matter has three main states:

• Solid: the atoms (or molecules) are very closely bound to each other.
• Liquid: the atoms (or molecules) can move in relation to each other.
• Gas: the atoms (or molecules) are far away from each other.

Atoms can also lose electrons and become ions. When matter consists of separate nuclei and electrons, we then refer to plasma.

Heating a body agitates the atoms/molecules and causes matter to pass from solid state, to liquid, and then gas. The temperature causing the transition from one state to another depends on the matter itself, but also the pressure conditions. A given quantity of matter (that is the same number of atoms/molecules) will take up more space in gas state than in liquid or solid state.