Question

how anhydrous copper sulphate can be used to detect whether the given liquid is water or not ?

Answer 1

The essential about test for water 



How to identify water in a substance ?

This question worth asking because a liquid doesn't necessarily contain water, and a solid substance may contains water wich is not observable with the naked eye.
A Test for water must be used identify water.
Different tests exist but the most commonly used requires anhydrous copper sulphate.
______________________________________ 

 
______________________________________

Anhydrous copper sulphate



The test for water requires a chemical compound: Copper sulfate anhydrous.
This is a white powder.
Comment: The term anhydrous is formed of "an" (privative prefix) and "hydrous" meaning "water": "anhydrous" is therefore almost synonymous with dehydrated.