Does Entropy Change with Constant Temperature Even If Heat Is Added?

  • Context: Graduate 
  • Thread starter Thread starter Antonio2090
  • Start date Start date
  • Tags Tags
    Entropy Temperature
Click For Summary
SUMMARY

Entropy can change even when temperature remains constant, particularly when heat is added to a system. Adding material or allowing for irreversible isothermal processes, such as free expansion of a gas into a vacuum, increases entropy. When heat is introduced while the volume expands and pressure drops, the available microstates increase, leading to a rise in entropy. The relationship between Gibbs Free Energy (ΔG = ΔH - TΔS) is crucial for understanding spontaneous processes at constant temperature and pressure, particularly in biochemical reactions involving ATP and GTP.

PREREQUISITES
  • Understanding of thermodynamic concepts, particularly entropy and isothermal processes.
  • Familiarity with Gibbs Free Energy and its equation (ΔG = ΔH - TΔS).
  • Knowledge of phase transitions and chemical reactions.
  • Basic principles of biochemical energy sources like ATP and GTP.
NEXT STEPS
  • Research the implications of irreversible isothermal processes on entropy changes.
  • Study the relationship between Gibbs Free Energy and spontaneity in chemical reactions.
  • Explore the role of ATP and GTP in biochemical energy transfer and entropy reduction.
  • Investigate phase transitions and their effect on entropy in various materials.
USEFUL FOR

Students and professionals in thermodynamics, physical chemistry, and biochemistry, particularly those interested in entropy changes and energy dynamics in chemical processes.

Antonio2090
Messages
1
Reaction score
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
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.
 
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:

\Delta G = \Delta H - T\Delta S

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 \Delta G 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.
 

Similar threads

Undergrad Focus Problem for Entropy Change in Irreversible Adiabatic Process
  • · Replies 60 ·
3
Replies
60
Views
10K
Undergrad Resulting temperature of mixed liquids
  • · Replies 5 ·
Replies
5
Views
2K
Undergrad The relationship between reversible and irreversible processes
  • · Replies 5 ·
Replies
5
Views
2K
Graduate Entropy change for spontaneous/ irreversible gas expansion
  • · Replies 4 ·
Replies
4
Views
2K
Undergrad Entropy change due to heat transfer between sources
  • · Replies 15 ·
Replies
15
Views
3K
Graduate Why is 0 K unattainable?
  • · Replies 11 ·
Replies
11
Views
1K
Undergrad Understand the Thermodynamic Identity: Is This Correct?
  • · Replies 3 ·
Replies
3
Views
2K
Undergrad Problem regarding understanding entropy
  • · Replies 3 ·
Replies
3
Views
2K
Undergrad Entropy after removing partition separating gas into two compartments
  • · Replies 9 ·
Replies
9
Views
3K
Graduate Free expansion of an ideal gas and changes in entropy
  • · Replies 2 ·
Replies
2
Views
3K