Question

Rivers flowing from mountain to field show no decrease in entropy.
If true enter $1$ , else enter $0$.

Answer 1

The entropy of a system is defined by the randomness of the movements of the molecule. In the question the randomness of the flow of the river doesn’t get affected by the flow of the water. As the state of water doesn’t change, therefore entropy doesn’t change.

Complete answer:
In the above given question, we have been asked what happens to the entropy of the system when the river flows down from the mountains to the fields.
First, we need to understand what entropy exactly means. Entropy is defined as the randomness of the molecules of the system. Now what exactly is entropy, it is a thermodynamic function and a state function. Now state function is a process which depends on the initial and final states of the system, not the process through which it went. When considering talking about entropy we don’t see any microscopic changes but see the system as a whole.
Now in the above given question as the river flows from the mountains to the plains, what happens to the entropy. Now as the initial state of water which is liquid and the final state of water which is liquid are the same therefore the randomness of the system doesn’t change and therefore the entropy of the system remains the same.
And hence the correct answer is 1 i.e. rivers flowing from mountains to plains show no change in entropy.

Note:
For comparing entropies of different systems, we need to observe the disorder in their whole system. If the disorder in the system increases, the randomness increases and therefore increases the entropy. This is the reason why gases have greater entropy than liquids and liquids have greater entropy than solids.