## Gas atoms

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

Frenz Cabison 1B
Posts: 54
Joined: Fri Sep 29, 2017 7:07 am

### Gas atoms

Can someone explain why gas atoms will never spontaneously go back to smaller volume? I sort of do not understand the concept behind this statement.

Lindsay Kester 2L
Posts: 29
Joined: Thu Jul 27, 2017 3:00 am

### Re: Gas atoms

Gas molecules will never go back to a smaller volume because it would decrease the entropy, or amount of states, of that system. In a smaller volume, there are less possible organizations for the molecules. Objects always want to go to a state of greater entropy, and moving to a smaller volume would decrease that.

Marina Georgies 1C
Posts: 30
Joined: Sat Jul 22, 2017 3:00 am

### Re: Gas atoms

Another way to think about it is how gases behave logically. They're not going to ever want to revert to a state where they have less space/freedom to move around. And a generally good rule of thumb is that gases are always going to want to go to a state of increased entropy, as explained in the previous reply.

Caroline LaPlaca
Posts: 30
Joined: Sat Jul 22, 2017 3:01 am

### Re: Gas atoms

maximum entropy is in the gaseous phase

Paula Sing 1J
Posts: 36
Joined: Fri Sep 29, 2017 7:06 am

### Re: Gas atoms

A real life example of this that might help you understand this would be spraying perfume in the corner of a room. It is "spontaneous" for the scent molecules to disperse throughout the room rather than to stay only in the corner. It is a lot like the diffusion of water across a membrane in biology.

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