1. Matter exists in three states: solid, liquid, and gas. One state can change into another through processes like melting, freezing, evaporation, condensation, and sublimation caused by heating or cooling.
2. Melting is when a solid is heated and changes to a liquid. Freezing is when a liquid cools and becomes a solid. Evaporation occurs when a liquid is heated and forms a gas, and condensation is the reverse process where a gas cools to a liquid.
3. Sublimation is when some solids like camphor and iodine change directly to a gas without becoming a liquid, through heating. They can also return directly to solids