What happens to the particles of matter when a liquid changes to gas

The particles are no longer held together by the attractive forces keeping it a liquid (hydrogen bonds in the case of water). Enough energy has to be put into the system to break these bonds. When this happens the particles pull apart and fill the space available as a gas

ptotal=pA+pB+pC

Explanation:

it is defined as the sum le the pressures le each individual gas ^