### Gibbs free energy

Posted:

**Tue Feb 19, 2019 12:29 am**Can someone explain the difference between Gibbs free energy and enthalpy/entropy/heat?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=135&t=42418

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Posted: **Tue Feb 19, 2019 12:29 am**

Can someone explain the difference between Gibbs free energy and enthalpy/entropy/heat?

Posted: **Tue Feb 19, 2019 1:02 am**

Gibbs free energy is a measure of energy contained within a system. More specifically, this energy is the energy in the system that can be accessed to do work.

Enthalpy is the measure of energy due to temperature.

Entropy is a measure of the number of quantum states that a system can occupy.

Heat is a transfer of thermal energy.

Enthalpy is the measure of energy due to temperature.

Entropy is a measure of the number of quantum states that a system can occupy.

Heat is a transfer of thermal energy.

Posted: **Tue Feb 19, 2019 11:24 am**

In terms of the equations, gibbs' free energy sees a relationship with enthalpy and entropy where delta G = Delta H - T * Delta. Heat is a measurement of how much energy is transferred, but in terms of energy that is not able to do work, whereas Gibbs free energy is a measurement of how much work something can do. Also, heat equals change in enthalpy under constant pressure conditions.

Posted: **Tue Feb 19, 2019 12:06 pm**

Gibbs free energy is not measured directly (like enthalpy is by a calorimeter). Rather, it is a calculated value that we get when we know enthalpy, entropy, and temperature.

Posted: **Tue Feb 19, 2019 12:33 pm**

You can think about Gibbs free energy as a conglomeration of enthalpy, temperature, and entropy because they are all related to energy and the amount of work a system can do, so the GFE equation brings them all together. Hope this helps :)

Posted: **Tue Feb 19, 2019 12:38 pm**

Gibbs free energy is the energy that is available to do work, unlike entropy/enthalpy/temperature, it cannot be directly measured.

Posted: **Tue Feb 19, 2019 12:42 pm**

Gibbs free energy is the amount of energy that is available to do work, and the equation shows the relationship between entropy and enthalpy as well.

Posted: **Tue Feb 19, 2019 12:48 pm**

Gibbs Free Energy is a concept developed to explain the energy within a system that is readily available to do work. It can't be directly measured and thus must be ascertained through calculations. When discussing the change in Gibbs Free Energy, we can say that if the value is negative, then the reaction is spontaneous at X pressure and Y temperature and if it's positive, then the reaction is not spontaneous at X pressure and Y temperature.