Question

why does the temperature on thermometer not rise till acetone is completely changed into vapors

Answer 1

Because thermometer contain mercury . Due to mercury it not rise or down. I hope it help you so please mark as brainlist

Answer 2

During the vaporisation of acetone (nail polish remover) the heat produced is used to overcome the forces of attraction during the change of state from liquid to gas.
This heat is called as latent heat of vaporization.
Latent heat means hidden heat.