Why is pumice stone added to the breaker while determining the boiling point of water?

Hint: Pumice is formed when hot mixes with water and results in a porous and abrasive stone which is perfect for sloughing away dry skin. Pieces of stone are added to water to avoid bumping of liquid.

Complete step by step answer:
The pieces of pumice stone are added to before heating to avoid bumping of liquid when the temperature rises. When water boils it releases energy in the form of bubbles. Moreover, if the bubbles are not formed, then the water will superheat and can possibly explode.
So, the main purpose of adding pumice stone is to facilitate the formation of bubbles so that “Bumping” can be prevented. It frequently happens, especially when the distillation has to be carried out under greatly reduced pressure, and that the liquid is liable to boil with bumping and thus we are able to measure the boiling point of water more accurately.
Adding pieces of rough stone gives lots of surface area for bubbles to form and release the energy gradually. Some pumice stones are as shown:


Note: A pumice stone can be used to remove the dead skin but these stones are so rough and can cause cuts, bleeding and soreness. They are also used as an abrasive, especially in polishes, pencil erasers and in the production of stone-washed jeans. Avoid pumice stones that are synthetically made, as they may contain undesirable chemicals.