Why does boiling occur only when vapour pressure = atmospheric pressure(in an open container)?

Question

unklerhaukus · Answer

well pressure is how much push .
if the atmospheric pressure is greater it will push the vapour back to liquid

xishem · Answer

Particles will generally flow from areas of high pressure to low pressure. Any particles that try to escape is pushed back down by the atmospheric pressure, essentially. Which is what UnkleRhaukus said.

If the vapour pressure is greater than (or equal) to the atmospheric pressure, then it will be able to overcome atmospheric pressure and push particles out of the vapour above the solution.