Smoke spontaneously spreads out from a cigarette to fill a room, but the reverse

Question

Smoke spontaneously spreads out from a cigarette to fill a room, but the reverse process is never observed to spontaneously occur (unless some force from outside the system acts). Consider various physical laws:

I: 1st Law of thermodynamics: Conservation of Energy

II: Conservation of Momentum

III: 2nd Law of thermodynamics: systems spontaneously evolve to more probable states.

The reverse process described above is never observed because it would violate:

A. III only

B. I, II, and III

C. I and III only

D. I and II only

***Give brief explanations of why you chose each of your answers.

Explanation / Answer

Spontaneous process favours direction in which change in Gibbs free energy is negative and change in entropy is positive .

This means that a process is spontaneous if entropy increases in the process .An increase in entropy means increse in randomness. So smoke in cigarette spreads because randomness of molecules increases in the process.

However to reverse the process means to abolish the randomness for which an energy is required to force a definite order by overcoming the randomness.so extra pressure is required.

This is direct consequence of second law of thermodynamics.

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