A substance may occur in different states of aggregation. At high temperatures and low pressures it occurs in gaseous form. At low temperatures and high pressures, it occurs in solid form. At intermediate temperatures and pressures, it may be a liquid. A gas is characterized by its high compressibility and low density. A solid and a liquid, in contrast, are less compressible, and have moderate or high densities. A solid, contrary to a liquid, offers resistance to deformation.