Same temperature and entropy

In summary, entropy can change even at constant temperature, as shown by the addition of material into a system or any irreversible isothermal process. Heating a system also increases its entropy, as seen through the increase in available microstates due to increased volume. The Gibbs Free energy, which is related to the chemical potential, can also indicate changes in entropy and whether a process is spontaneous or not. In biochemical reactions, non-spontaneous reactions are often powered by using the energy in ATP or GTP, which are kept at concentrations far from equilibrium.
  • #1
Antonio2090
1
0
Does entropy change when temperature remains constant? What if heat is added into a system, while the volume expands and the pressure drops at a constant temperature? Is there any change in entropy?
 
Science news on Phys.org
  • #2
Does entropy change when temperature remains constant?

Yes, entropy can change even at constant temperature. For example, adding material into a system increases entropy, as does any irreversible isothermal process such as free expansion of a gas into a vacuum.

What if heat is added into a system, while the volume expands and the pressure drops at a constant temperature? Is there any change in entropy?

Yes, heating a system always increases its entropy. Another way to view this process is that the temperature is the same, but the space for atomic motion has increased because the volume increased. There are therefore more available microstates for the system, which is equivalent to saying the entropy has increased.
 
  • #3
Antonio2090 said:
Does entropy change when temperature remains constant? What if heat is added into a system, while the volume expands and the pressure drops at a constant temperature? Is there any change in entropy?

It can. For example, let's look at the Gibbs Free energy- this is the change of free energy for processes occurring at constant T and P:

[tex]\Delta G = \Delta H - T\Delta S[/tex]

G is the Gibbs free energy, H the enthalpy, T temeprature, S entropy. There are lots of processes that use this relationship: phase transitions, chemical reactions, etc. The sign of [tex]\Delta G[/tex] tells you if the processes is spontaneous or not- in biochemical reactions, non-spontaneous reactions are generally powered by using the chemical energy in adenosine triphosphate (ATP) or guanine triphosphate (GTP)- but not in the way elementary texts describe.

The Gibbs free energy is related to the chemical potential: specifically, if a chemical is out of equilibrium concentrations. The relative concentration of ATP to ADP is kept about 10^10 times out of equilibrium by organisms (IIRC), and this is the source of energy used to power reactions, and by which we have the ability to locally decrease our entropy.
 

1. What is the relationship between temperature and entropy?

The temperature and entropy of a system are directly proportional. This means that as the temperature increases, the entropy also increases. Conversely, as the temperature decreases, the entropy decreases.

2. Why does entropy increase at the same temperature?

Entropy is a measure of the disorder or randomness in a system. At the same temperature, molecules have more energy to move around and become more disordered, increasing the overall entropy of the system.

3. How does entropy affect the behavior of a system?

As the entropy of a system increases, the system becomes more chaotic and less predictable. This can result in changes in physical and chemical properties, such as phase transitions or chemical reactions.

4. Is it possible for two systems at the same temperature to have different entropies?

Yes, it is possible for two systems at the same temperature to have different entropies. This is because the entropy also depends on the number of particles in the system and their arrangement.

5. Can the entropy of a system decrease at the same temperature?

Yes, the entropy of a system can decrease at the same temperature. This can occur through a process called spontaneous ordering, where the particles in a system become more ordered and decrease in entropy without any external input of energy.

Similar threads

Replies
56
Views
3K
Replies
4
Views
890
Replies
15
Views
1K
  • Thermodynamics
Replies
3
Views
748
Replies
3
Views
958
Replies
2
Views
1K
Replies
9
Views
1K
  • Thermodynamics
Replies
3
Views
1K
Replies
22
Views
2K
  • Thermodynamics
Replies
4
Views
277
Back
Top