Ineed on this exam question.
water is a pure substance. which of the following is true about water?
a: a chemical change is required to separate the elements present in it.
b: a physical change is required to separate the elements present in it.
c: it is made up of two compounds, each with a different set of atoms.
d: it is made up of an element and a compound.

Option (A) is the correct answer.

Explanation:

A compound is defined as the substance in which two or more different atoms chemically combine together in a fixed ratio by mass.

For example, molecular formula of water is and it is a compound as there is chemical combination between hydrogen and oxygen atom.

They are combined in a ration of 2 : 1. These atoms can only be separated through a chemical change and not by any physical means.

Thus, we can conclude that the statement a chemical change is required to separate the elements present in it, is true about water.