Solid: constant shape and volume of material that is not easily deformed state.
Had a constant volume: liquid, but did not have some form of substance.
Gas: did not have a regular shape, by volume changes in temperature and pressure.
The best thing to distinguish between solid, liquid, gas, intermolecular array. Solid, as you know, very strong people are free solid rather than liquid molecules are tied together still tied. Gas freely move around very little intermolecular attraction. Commonly solid, liquid eye can see, but we should be able to see the gas. And another thing is a solid or liquid phase is not affected by temperature and pressure, but the gas maven.
Change of state
Solid-liquid (fusion) liquid-solid (coagulation) liquid-gas (vaporization) of gas -> solid-liquid (liquefied) gas (sublimation) solid -> gas (sublimation)
Fusion to change a solid to a liquid. ex), heat the butter melts.
Solid changing to gas is sublimation. ex) by placing the dry ice disappears. Naphthalene hang vanishes.
Liquid turns into a solid clot. Hardens ex) the melted chocolate and place it in the refrigerator.
Vaporizing the liquid to turn into a gas. ex) Laundry dries.
Liquefied gas turns into liquid. ex) look out the window at dawn dew maethyeo.
Sublimated gas turns into a solid. ex) a cold day outside, Surrey.