Question

Crystallisation is an example of a ________.
A. Physical change
B. Biological change
C. Chemical change
D. Fundamental change

Answer 1

Hint: Try to recall that crystallization is the solidification of atoms/molecules into a structured form called a crystal and it is a better technique for the separation of mixture.

Complete step by step solution:
- Crystallization is a process where we obtain the pure crystallized form of a compound that was originally impure.
- The impure substance is dissolved in a solvent in which it is sparingly soluble at room temperature and appreciably soluble at high temperatures. The solution is heated so that all the substance is dissolved and then filtered so that the cooled crystals can be seen on the filter paper.
- This process can be reversed by adding a solvent to the crystals in which the substance can dissolve completely. Thus, crystallization is reversible.
- We know that chemical and fundamental changes are not reversible. Crystallization is a process that can occur without any relation to biological organisms. Physical changes on the other hand are reversible.

Hence, we can say that the correct option is ‘A. Physical change’

Note: Remember that if the compound and the impurities have comparable solubilities, then repeated crystallization is necessary to purify the substance. If a solvent is added to a recently crystallized substance, just evaporation of the solvent will not give you crystals. The substance will have to undergo recrystallization to reverse the process.