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The molecule

The molecule and the different states of matter

Atoms held together by chemical bonding are called molecules. These are so small that, for example, 1 mm3 of air at atmospheric pressure contains approx. 2.55 x 1016 molecules.

All matter can in principle exist in four different states:

  • Solid state
  • Liquid state
  • Gaseous state
  • Plasma state

In the solid state the molecules are tightly packed in a lattice, with strong bonding. At all temperatures above absolute zero a certain degree of molecular movement occurs, in the solid state as a vibration around a balanced position, the faster the greater the temperature becomes.

When a substance in a solid state is heated so much that the movement of the molecules cannot be prevented by the rigid pattern (lattice), they become loose the substance melts and transforms to a liquid.

If the liquid is heated more, the bonding of the molecules is broken, and it transforms into a gaseous state during expansion in all directions and mixes with the other gases in the room. When gas molecules are cooled, they loose speed and bond to each other again, and condensation starts.

However, if the gas molecules are heated further, they are broken down into individual particles and form a plasma of electrons and atomic nuclei.