Exothermic and Endothermic vs Exergonic and Endergonic (simplified)

One of the most common things I come across when working with students studying for the MCAT, PCAT, DAT, AP, and college level chemistry courses is understanding the differences between endergonic and exergonic vs. endothermic and exothermic.

Before we get into the differences lets point out what they have in common: energy is going somewhere. In both thermic and ergonic processes energy is either going in or out. The major difference being what kind of energy is moving in and out, and the details of that energy movement.

I am going to assume that if you are asking the difference between exo(endo)thermic and exer(ender)gonic you are probably familiarized with the differences between enthalpy, entropy, and gibbs free energy. In case you need a refresher here it is:

Entropy, S

For our discussion, Entropy is a measurement of disorder.

Enthalpy, H

The changes in potential energy involved in any process of transformation, such as breaking and forming chemical bonds in a reaction.

For our discussion we can just conflate this with the flow of heat under constant pressure conditions: see below.

Gibbs free energy, G

The energy of a chemical reaction you can use to do work.

When we measure changes such as exothermic or endothermic processes: we are measuring changes in potential energy involved in the formation and breaking of chemical bonds in a particular reaction (exo and endothermic).

AN: If you are really into the detailed differences between enthalpy of reaction from enthalpy of formation, click here. For our discussion ill just identify them as the same since they have little relevance to understanding the definition of exo and endothermic.

Changes in enthalpy: either exothermic or endothermic manifest themselves as the flow of heat ( changes in kinetic energy of particles in our reaction) under constant pressure conditions, and can be measured as changes in potential energy circa the first law of thermodynamics and the definition of enthalpy. ******

So in exothermic and endothermic processes POTENTIAL ENERGY is changing as energy flows in and out.

[Frida]

Short, to the point, and exactly what I was looking for (perfect title). Thank you!
I'm terrible with definitions so a mnemonic I use is exoTHermic = enTHalpy and exerGonic = Gibbs

[SimpleMathematics]

I learned a lot thank you very nice video

[akakakaka]

I think im understanding the end/exo stuff. So far this is what I know:

When a chemical reaction takes place: heat energy (q) can either be lost or absorbed. When we have constant temp & pressure q = ∆H

∆H enthalpy: this is the change in potential energy ( heat energy) b/w products & reactants. If ∆H (endothermic) that means heat energy was absorbed in the reaction in order to make products and products will be at a higher energy state than reactants.
If -∆H (exothermic) this means heat energy was released when making products and products are at a lower state.


Now, the potential energy which is lost/gained in a chemical reaction has the ability to do WORK.

How do we figure out the energy that’s able to do work? This is the FREE ENERGY ∆G.

Now, remember, in any chemical reaction, some energy is lost due to entropy (this is the energy that is unable to do work).

So, to figure out the amount of energy that’s able to do work (ie. Free energy): ∆G = ∆H - T∆S.


1) Is this all correct/wrong?
2) am I missing anything or does anything needed to be added?
3) the energy which is lost & unable to do work, is that entropy? b/c i thought entropy is disorder.
4) if we have + entropy, does that mean we gained energy that is unable to do work?

im trying to figure out what energy which is unable to do work means.

[TraveloH]

Thank you so much for this video... You described everything beautifully...

[ying]

So is exothermic and exergonic related??