Question

I the temperature of boiling water constant even though it is beig heated

Answer 1

The boiling point is the temperature at which the vapour pressure of the liquid is equal to the atmospheric pressure  

When the temperature of water is raised, the vapour pressure of water molecules increases and reach a certain pressure where the vapour pressure of the water is equal to the atmospheric pressure. Thus both vapours are in equilibrium and thus no change in the boiling point. Boiling point changes only when all the water is converted to water vapour