Question

What makes water evaporate in vacuum....pls explain at molecular level and also how pressure affects change of state of matter....pls explain at molecular level

Answer 1

Because of reduction in pressure. This lowers the relative vapor pressure and the water changes phase into a gas. What you are effectively doing, by pumping out the air, from a chamber containing a bowl of water; is removing the gaseous water from the local atmosphere (for the water bowl). Since you removed those gases, the equilibrium must be regained, so water evaporates and fulfills the requirement.