Change in entropy for certain processes (conceptual problem)

In summary, the conversation discusses the possibility of having a process that is both adiabatic and irreversible, and whether it is possible for a change in entropy to be reversible with heat transfer. The equation for entropy is mentioned, and the concept of adiabatic and irreversible processes is explained. The conversation also touches on the relationship between friction and heat transfer, and the possibility of heat being put into a system and then taken out while remaining reversible.
  • #1
joshuat
1
0

Homework Statement



for change in entropy is it possible to have a process that is both adiabatic and irreversible?
is it possible for change in entropy to be reversible with heat transfer?
what are the changes in entropy if possible?
if you can answer please explain why

Homework Equations



S=Q/T

The Attempt at a Solution


adiabatic means no heat transfer. Irreversible means that there is friction in the process. Entropy is a thermodynamic property that is a measure of the energy not available for useful work.

for the first question I'm just wondering if friction is a form of heat transfer. I'm pretty sure it is so I want to say it is not possible.

for the second question i think it is nonzero. not sure if positive or negative. I think heat can be put in a system and then taken out while still remaining reversible.


 
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  • #2
Hi joshuat, welcome to PF!

joshuat said:
Irreversible means that there is friction in the process.

More generally, a process is irreversible if there's a difference in temperature, pressure, or any other intensive variable within the system. So consider a gas that's allowed to expand into a vacuum: we can insulate the system so that it's adiabatic, and the expansion into a larger space is certainly irreversible.


joshuat said:
I think heat can be put in a system and then taken out while still remaining reversible.

Agreed, so long as the temperature difference is negligible.
 

1. What is entropy and how does it relate to change in a process?

Entropy is a measure of the disorder or randomness in a system. It relates to change in a process by indicating the direction in which a process is most likely to occur. A process will tend to increase the entropy of the system, meaning that the system becomes more disordered or random.

2. How is change in entropy calculated for a process?

The change in entropy for a process can be calculated using the formula ΔS = Q/T, where ΔS is the change in entropy, Q is the heat added or removed from the system, and T is the temperature in Kelvin.

3. Is the change in entropy always positive for a spontaneous process?

No, the change in entropy can be negative for a spontaneous process if the heat being released by the system is greater than the heat being absorbed.

4. What factors affect the change in entropy for a process?

The change in entropy for a process can be affected by the temperature, pressure, and volume of the system, as well as the types and amounts of substances involved in the process.

5. How does the concept of entropy relate to the Second Law of Thermodynamics?

The Second Law of Thermodynamics states that the total entropy of a closed system will always tend to increase over time. This means that in any spontaneous process, the overall entropy of the system will increase, indicating an increase in disorder or randomness.

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