Which is not a property of a pure substance? uniform composition varying composition fixed composition

Option (b) is the correct answer.

Explanation:

A pure substance is defined as a substance that consists of fixed composition of atoms.

For example, NaCl is a pure substance as it contains same composition of sodium and chlorine atoms.

Whereas a substance which has varying composition of atoms is known as a mixture. For example, mixture of sand in water.

Thus, we can conclude that varying composition is not a property of a pure substance.

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.