Question

How boiling is a bulk phenomenon whereas evaporation is a surface phenomenon?

Answer 1

Boiling is a bulk phenomenon. Particles of the bulk of the liquid gain enough energy to change to vapour state. The entire bulk of liquid and all the molecules including the interior and the surface gain energy to change to vapour state. The heat energy is supplied from the bottom of the liquid. Therefore the heat energy goes to the entire bulk of liquid and starts boiling. Whereas evaporation is a surface phenomenon. Only the particles on the surface gain enough energy to get converted into vapour state. A small fraction of particles at the surface gain energy and break away from the force of attraction of the other particles and changes to vapour state.