They are lighter in density as compared to solids. Gas are compressible, whereas not all solids. Gases exhibit better flow characteristics than solids. Gases readily react with other substances. All solids are seen by the naked eye whereas some gases are not.
The solubility of solids generally gets higher as the temperature gets higher. (apart from with calcium hydroxide- limewater). The opposite is true for gases- their solubility decreases as the temperature increases.