In nature, as long as temperature is above the absolute zero (0 Kelvin or -273^oC) all molecules possess kinetic energy or energy of motion. In other words, they move, wriggle and giggle at random. The three state of matter (solid, liquid and gas) differ with respect to the freedom of movement of their constituent molecules: this is what makes a solid "solid", a liquid "liquid" and a gas "gaseous".

The molecules of a solid are closely packed and the forces of attraction between molecules allow them to vibrate but not to move around.

In a liquid, the molecules are farther apart, the attractions between molecules are weaker and the molecules move about with considerable freedom.

In a gas, the molecules are so far apart that intermolecular forces are negligible and molecular movement is not restricted at all by neighbouring gas molecules.

Molecules in liquids and gas move around in a perpetual random fashion. They are in constant motion, they move about randomly at high speeds, they collide and ricochet off one another changing direction with each collision. The number of molecules going in a given direction is balanced by the number of molecules going in the other direction and thus even though molecules are moving around they are evenly distributed.