Why ethyl alcohol is vapor?

Answer 1

It's not technically speaking, a vapour. But it is a volatile liquid (It readily evaporates). Boiling point is to do with the interactions between the molecules in a liquid. The stronger the interaction, the more energy is required to pull them apart. So the energy (heat) supplied at it's boiling boiling point is sufficient to break the interactions in ethanol. The boiling point of ethanol is 78.1 °C.

Answer 2

Ethyl alcohol vaporizes due to its relatively low boiling point of 78.37°C. When exposed to heat, the molecules gain enough energy to break free from the liquid phase and become gas molecules.