Question

Why is the bulb of the thermometer kept above the surface of water while determining the boiling point of water?

Answer 1

bulb of a thermometer is always kept above the surface of water while determining the boiling point so as to make sure that the bulb doesn't breaks due to very high temperature
if the bulb is kept inside the boiling water it may break and the temperature cannot be taken.
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hope it helps.....

Answer 2

the water taken in the round bottomed flask may contains some impurities while steam produced due to boiling of water is always pure .so in order to get the correct boiling point of pure water the bulb of the thermometer is kept in the steam of water above it