If a hot, saturated solution of copper sulfate is cooled rapidly in ice-cold water, smaller and less well-formed crystals will form than if it is cooled slowly at room temperature. How would you design and perform an experiment to test this hypothesis?
(Hint: Prepare a hot saturated solution of copper sulfate and divide it into two equal parts.) [Pg. No. 79]

Aim: To compare the size and shape of copper sulfate crystals formed by rapid cooling and slow cooling of a hot saturated copper sulfate solution.

Materials required: Copper sulfate, water, beaker, glass rod, filter paper, two equal test tubes/beakers, ice-cold water bath, thread/seed crystal, and a magnifying lens.

Procedure:

(1) Prepare a hot saturated solution of copper sulfate by dissolving copper sulfate in hot water until no more solute dissolves.

(2) Filter the hot solution to remove undissolved impurities.

(3) Divide the solution into two equal parts in two clean beakers or test tubes.

(4) Keep the first part in an ice-cold water bath so that it cools rapidly. Keep the second part undisturbed at room temperature so that it cools slowly.

(5) After crystals form in both setups, separate them and observe their size and shape using a magnifying lens.

Observation: The solution cooled rapidly in ice-cold water forms smaller and less well-formed crystals, while the solution cooled slowly at room temperature forms larger and better-shaped crystals.

Conclusion: The hypothesis is supported. Slow cooling gives more time for copper sulfate particles to arrange themselves in a regular pattern, so larger and well-formed crystals are produced. Rapid cooling causes quick crystallisation, resulting in smaller and less regular crystals.