## entropy and spontaneity

Boltzmann Equation for Entropy: $S = k_{B} \ln W$

Miranda 1J
Posts: 51
Joined: Fri Sep 29, 2017 7:06 am

### entropy and spontaneity

In the book it says "A process is spontaneous if it is accompanied by an increase in the total entropy of the system and the surroundings" I know it sounds stupid but I don't get this, can someone explain what exactly is meant by this?

Jiun Yue Chung 2I
Posts: 27
Joined: Fri Sep 29, 2017 7:06 am

### Re: entropy and spontaneity

I think that a good way to think about this concept is to remember the picture of the gas contained in a flask (blocked by a valve that prevents it from diffusing to the rest of the flask). When you open the valve, the gas diffuses out into the rest of the flask and therefore, entropy has increased in the process as the number of possible states has increased for the gas molecules. This process then, is considered spontaneous because if you recall, a spontaneous process is one that doesn't require any driving force to move those molecules to diffuse into the rest of the flask.

On the other hand, you would probably need energy to move the system from a state of high entropy to lower entropy (ie: putting all the gas molecules behind the valve) and therefore, it's non-spontaneous as it is driven by some other force to accomplish the task. Hope this helps :)

Return to “Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy”

### Who is online

Users browsing this forum: No registered users and 2 guests