Density

The difference between the densities of solids, liquids and gases is due to the distance between the particles in each state of .

The particles of a solid are very close together.

It melts when it changes from the solid state to the liquid state.

The particles remain close together, so there is usually only a small increase of .

The same mass of liquid will have slightly greater volume than the solid.

As density equals \(\frac{\text{mass}}{\text{volume}}\), the liquid will have slightly lower density.

The density of solid iron = 7.8 g/cm³

The density of liquid iron = 6.9 g/cm³

A substance evaporates when it changes from the liquid state to the gas state.

Its particles move freely and are very far apart, so there is a large increase of volume.

The same of gas will have very much greater volume than the liquid, and so will have much lower density.

The density of liquid oxygen = 1.1 g/cm³

The density of gaseous oxygen = 0.0014 g/cm³

State	Distance between particles	Density	Density in g/cm³
Solid	Very close together	High	Solid iron = 7.8
Liquid	Slightly further apart than a solid	Slightly less than the solid	Liquid iron = 6.9
Gas	Very much further apart than a solid or liquid	Very much less than the solid or liquid	Oxygen gas = 0.0014

State	Liquid
Distance between particles	Slightly further apart than a solid
Density	Slightly less than the solid
Density in g/cm³	Liquid iron = 6.9

State	Gas
Distance between particles	Very much further apart than a solid or liquid
Density	Very much less than the solid or liquid
Density in g/cm³	Oxygen gas = 0.0014

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