Why Is the Delta G Positive in Hydrophobic Interaction with Water?

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SUMMARY

The discussion centers on the thermodynamics of hydrophobic interactions, specifically the positive delta G (ΔG) observed when oil and water interact. Participants clarify that a positive ΔG indicates that free energy is required for the system to reach a more ordered state, as water molecules form structured arrangements around oil. Despite the positive ΔG, the negative delta H (ΔH) signifies that the process is exothermic, leading to confusion about the relationship between these thermodynamic parameters. Ultimately, the spontaneous separation of oil and water suggests that the overall Gibbs free energy decreases, aligning with thermodynamic principles.

PREREQUISITES
  • Understanding of Gibbs free energy (ΔG) and its implications in thermodynamics.
  • Knowledge of enthalpy (ΔH) and exothermic vs. endothermic reactions.
  • Familiarity with hydrophobic interactions and molecular behavior in mixed solutions.
  • Basic principles of thermodynamic spontaneity and equilibrium.
NEXT STEPS
  • Research the relationship between ΔG, ΔH, and entropy (ΔS) in thermodynamic processes.
  • Explore the concept of hydrophobic effect in biological systems, particularly in protein folding.
  • Study the role of temperature in influencing ΔG and ΔH during phase separation.
  • Investigate experimental methods to measure ΔG in various chemical systems.
USEFUL FOR

Chemistry students, biochemists, and anyone studying thermodynamics and molecular interactions, particularly in the context of hydrophobic effects and phase behavior in mixtures.

lha08
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Homework Statement


So like let's say oil and water are interacting together. I know that they do not readily interact together and so water aggregates in a more ordered state around the oil.
But then this is where I'm confused;
-They say that the delta G (change in free energy) is positive, so that means free energy is required. Do they mean the energy is required to make the water molecules into a more ordered state?
-Then they apparently the delta H (change in enthalpy) is negative, because the reaction is exothermic...like I am confused...if the free energy is positive and requires free energy, wouldn't the delta H be positive indicating an endothermic reaction?


Homework Equations





The Attempt at a Solution

 
Physics news on Phys.org
Who says that [itex]\Delta G>0[/itex] when an oil-water mixture separates? It happens spontaneously, so the Gibbs free energy must decrease.
 

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