Question

Addition of another crystal of the same substance to a water solution does not change the crystal. What were their particles doing ?
A.Going into an unsaturated solution
B.Causing the solution to become saturated
C.Not going into the solution into this static condition
D.Exchanging places with others in the solution

Answer 1

A crystal is defined as a form of crystalline solid that is made up of atoms and molecules. It forms a lattice and it is the microscopic arrangement of atoms .

Complete answer:
Before talking about the answer, we should talk about crystals.
-Crystals are present in a crystalline form which has definite shape and size. They are made up of ions, molecules and atoms. The process that forms crystals is called the crystallization process. In this process solid materials are formed from another phase mainly from liquid. The materials formed are rigid. The crystallisation process is widely used in industry for purification and separation processes. There are two major events of crystallisation process:
-Nucleation : in a defined manner, the molecules gather together to form a cluster. These molecules should achieve critical cluster size otherwise it will redissolve.
-Crystal growth: when a molecule acquires a crystal cluster size, then it begins to increase in size. Supersaturation and supercooling is the reason behind the formation of crystals.
-Recrystallisation process is defined as the addition of a solid compound to a hot solution which is later cooled down and forms a pure crystal. The impurities will remain in the solution.
-When there is an addition of another crystal of the same substance to a water solution, it does not change the crystal because the particles were exchanging places with others in the solution. Because of this exchange, the number of particles present in the crystal remains the same.
Therefore, the correct option is D.

Note:
-Recrystallisation process is used for purification of a solid which later forms a crystal.
-Supersaturation is a process when the concentration of solute exceeds the concentration by the value equilibrium solubility.
-Crystals are crystalline forms of material in which atoms and molecules are arranged in a systematic manner forming a crystal lattice.