Pure water has a fixed boiling point of `100^(@)C` under standard atomspheric pressure. This fact can be used to confirm that a colourless liquid giben to us is water as followis: We take the colourless liquid in a distillation flask fitted with a thermometer. Let us heat the flask with a gas burnet till hte liquid starts boiling. If all the colourless liquid distils over (or boils off) at the sme temperature of `100^(@)C,` without leavbing behind any residue in the distllation flask, it will be pure water.
