Explanation:
Degree of randomness is known as entropy. More is the collision between particles more randomly they will move from one place to another.
Hence, more will be entropy of the substance.
In system A, when solid particles will dissolve in water then it means particles of solid will change into ions. Hence, they will move rapidly from one place to another. This shows that entropy of system A has increased.
In system B, when vapor of a gas is condensed then it means gaseous state has changed into liquid state. In gases state, molecules have more kinetic energy and they move rapidly.
But in liquid state, molecules come closer to each other and they attain less kinetic energy as compared to molecules in a gaseous state.
This means that entropy decreases in system B.