Suggest A Way To Determine Whether A Colorless Liquid Is Pure Water Or A Salt Solution Without Tasting It?

A physical test for pure water will be to determine its boiling point:
You boil the liquid gradually and if it boils exactly at 100 degrees C then it's pure water.
A chemical test would be:
Apply a piece of anhydrous copper sulphate paper to the liquid.if it's pure water you're dealing with then the paper will turn from white to blue.