How would you confirm that a colourless liquid given to you is pure water?
Every liquid has a fixed boiling point.
Pure water has a boiling point of 100 degree celsius/373K.
Hence, to verify if the colourless liquid is pure water, we’ll boil it and observe its boiling point.
If the liquid starts boiling at a sharp 100 degree celsius/373K, then the colourless liquid will be pure water.