# Entropy concept

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1. Oct 5, 2014

### Arun Raja

1. The problem statement, all variables and given/known data
http://puu.sh/c09sc/b1d02302bd.png [Broken]

2. Relevant equations
Conceptual question.

3. The attempt at a solution
but heat does not decrease due to isothermal process and expansion leads to lesser collision of particles on walls of container.
So why D?

Last edited by a moderator: May 7, 2017
2. Oct 5, 2014

### Doug Huffman

Is not your question really, "Why not A, B, or C?

The compression processes are intuitively obvious? Adiabatic processes do not transfer heat or matter.

3. Oct 5, 2014

### Arun Raja

even isothermal processes occur at same temperatures. So there is no increase in internal energy which leads to increase in entropy.

4. Jun 22, 2015

### Jac man

Think of it with this equation from the 2nd law of thermodynamics:

ΔS = Q/T

For adiabatic processes, Q = 0.
For isothermal processes, entropy of the system will increase if the system is expanding because Q must be positive (heat goes into the system) for the system to remain isothermal. If the system is compressed isothermally, heat must go out of the system and entropy will decrease.