Why do states of matter change?
States of matter Change due to surroundings or favourable conditions .
As we all know nothing in universe changes by its own . There is always a reason foreven a simple change also . So mattter changes its state due to change in surroundings.i.e.changein temp. , change in pressure etc.
Like when the temperature increases the intermolecular spaces increases so the matter change its form.if it is solid it will become liquid , if it is liquid it will become gas .