Solid to liquid = fusion,liquid to gas=vapourisation ,gasto solid=sublimation,liquid tosolid = solidification, gasto liquid= condensation and gas to liquid is as same its my view its a small example all of them are know that i think so just u accept this i think or not that,s ur wish
Take a white paper and draw a square with a length of 10cm.
Now take small thermocol balls or the stickers which your mother keeps on her forehead and stick them very close to each other which shows that the molecules in a solid are tightly packed
Now do the same thing for liquids and gases but the space between the balls or stickers must be slightly less than that of solids in liquids and the gap should be very more in gases.
This is a simple way to show the model of solids liquids and gases