Question

do all substances change from solid to liquid and liquid to gas on heating ? explain

Answer 1

No, substances like napthalene doesnot under goes into liquid state. It directly changes into gaseous state. Those substances are called sublimable substances.

Answer 2

it is not necessary that a substance will convert into solid to liquid or liquid to gas . there is also some substances which convert from solid to gas directly on heating. these all things depend upon the intermolecular attraction b/w the substance if is stronger enough, as in solid ,then it will first convert into liquid then on further heating into gas.