what may happen if the bulb of thermometer is dipped below the surface of water while determining boiling point of water
Answers
A pot of boiling water is actually slightly higher than the boiling point. I know, that doesn't make sense. Let me explain. The boiling point is defined as the temperature at which the vapour pressure is exactly equal to the external pressure. The “Normal Boiling Point” is the boiling point at exactly 1 atm of pressure. If you look closely at a pot of boiling water you'll notice bubbles rising from the bottom of the pot. Those bubbles are pure water vapour and since they have pushed back the water that is on top of themselves and the air over the water, they must have had a pressure greater than the external pressure to do that. Those bubbles will stop expanding when the pressure just exactly equals the boiling point and will stay there as they finish rising in the pot. This, the steam just above the water will be a better measure of the boiling point because it will not yet have had a chance to cool down.