Question

Some substances can’t exist in the gaseous state other can’t exist in the liquid state and some can’t exist either in the gaseous or the liquid state gives suitable examples justify the above statement

Answer 1

Carbon dioxide, for example, can exist in a solid state (commonly known as "dry ice") and if heated, it turns into a gas, without going through the liquid state. However, that does not mean that carbon dioxide cannot form a liquid under any circumstances. For every chemical, there is what chemists call a "phase diagram" which shows the different phases (solid, liquid, and gas) which exist under different combinations of temperature and pressure (pressure normally refers to air pressure, although other kinds are possible). Almost any chemical is capable of forming any phase under the right combination of temperature and pressure. The only exception is helium, which has no solid phase. It can be a gas or a (very cold) liquid, but not a solid. That is because helium is the most inert of all inert elements, and it has extremely little inter-atomic attraction, which is insufficient to form a solid phase even at the coldest possible temperature