CHEMISTRY COMMUNITY

Hi!
I always forget the difference between endothermic and exothermic reactions. Does anyway have an easy way to remember them?
Thanks!

(Claire Woolson Dis. 1K)

ClaireHW wrote:Hi!
I always forget the difference between endothermic and exothermic reactions. Does anyway have an easy way to remember them?
Thanks!

(Claire Woolson Dis. 1K)

Endo- is the root for within/inside, so this would be taking heat in.

Exo- is the root for outside, so this would be releasing heat.

Hope this helps :)

I remember that exothermic is the RELEASE of heat because of the ex- , which is similar to EXIT.
Endo- itself means internal or within, so you can think of the heat being put "within" the system.
Maybe this helps?

The signs related to exo and endothermic reactions make sense once you understand what each process means. It makes sense for the loss of heat (exothermic) to be negative and the gain of heat (endothermic) to the positive.

Another comment on this is when you're solving for the change in enthalpy for example, a negative value for kilojoules means that the reaction was exothermic and a positive value for kilojoules means that the reaction is endothermic.

For me I think about how they sound. The "en" in endothermic sounds like in and the "ex" in exothermic reminds me of exit.

This also still sometimes confuses me, and it has since high school. In particular, I had issues with knowing what side of the reaction heat was on. I remember it now as endothermic meaning heat entering (heat is required) and exothermic as heat exiting (heat is a product).

I use the prefixes, Ex->exiting heat, en-> entering heat or needing heat.

Also exothermic is when there's a negative delta H compared to endothermic where theres a positive delta H because endothermic heat is being added.

I remember that endothermic reactions require/absorb energy because of the root (endo) and that they have a positive delta H because if they absorb energy, then the final product of the reaction will have more energy than the initial reactants (change = final - initial). Exothermic reactions release energy (root: exo-) and they have a negative delta H because if energy is being released, then the final product will have less energy than the initial reactants. I personally used to have a hard time linking endo- and exothermic reactions to bond breaking and forming, but now I remember that breaking a bond requires/absorbs energy (like you have to use energy to karate chop a wooden board or break a pencil), so the process of breaking a bond is endothermic and has a positive delta H.

Endo sounds like into so heat moving into it vs. exo which sounds like exit which means the heat is being moved out of whatever it may be.

Also in chemistry, exothermic and endothermic refers to the system. Exothermic releases heat (so the surroundings feel warm) and endothermic requires heat (so the surroundings feel cool)

On top of what the others have posted, I think it's also very important to come up with a way to remember that endothermic reactions break bonds and exothermic reactions form bonds. For me, I just imagine in my head the game of pool when the cue ball is used to break at the beginning of the game. The cue ball enters (endothermic) into the group of other balls, causing them to break.

A quick way I use is "into endo" and "exhale exo". Heat goes into the system during an endothermic reaction and heat is exhaled during a exothermic reaction.

I usually remember it with words similar to it such as "endo" as enter = heat entering the system and "exo" as exit = heat escaping the system.

Adding to what everyone else has said and like someone said, it is also important to see how these terms refer to a reaction.

If the reaction is exothermic, you are releasing heat, meaning that on the products side of your reaction you could add heat. Meanwhile, if the reaction is endothermic, you are taking in heat, meaning that on the reactants side you could add heat. Without heat being supplied the endothermic reaction would not occur.

I personally remember it from the acronym MEXOBENDO where the M stands for making and the B stands breaking. This gives you Making(bonds) EXOthermic and Breaking ENDOthermic

I remember endothermic and exothermic by memorizing that endothermic "absorbs heat" and exothermic "loses heat".

This post has really helped me remember the difference between the two!

think in terms of where the heat is added or where the heat is released.

endothermic
A+HEAT-> B+C


exothermic

A+B -> HEAT + C

For me remembering definitions through phonetic tricks/associations is pretty helpful. I remember exothermal by thinking how exo is like exo skeleton and how exoskeletons are on the outside, just like how in an exothermal reactions the heat moves to the outside of where it formerly was. Then I remember endothermal by just knowing its the opposite, with heat moving inward.

For me remembering definitions through phonetic tricks/associations is pretty helpful. I remember exothermal by thinking how exo is like exo skeleton and how exoskeletons are on the outside, just like how in an exothermal reactions the heat moves to the outside of where it formerly was. Then I remember endothermal by just knowing its the opposite, with heat moving inward.

The "en-" in endothermic sounds like enter, as in heat is entering, and the "ex-" in exothermic sounds like exit, as in heat is exiting.

You can use prefixes!

ENdo = heat ENtering --> Because heat is coming in, then the outside will be colder.

EXo = heat EXiting --> Because heat is going out, then the outside will be warmer.

"En" kinda sounds like "in" and "ex" means "exit".

The Ex- in exothermic is like the ex- in exit, so heat is leaving the system into the surroundings. Once you know that exothermic is when heat leaves the system, that means endothermic is when heat enters or is absorbed by the system.

The prefixes of the words determine what the meaning of them. "En"dothermic sounds like "In"dothermic, which means that heat is being absorbed and "Ex"othermic means exit, so heat is being released.

I usually think about the prefixes. The "en" in endothermic sounds like in and the "ex" in exothermic reminds me of exit.

Exothermic and exit start the same so its like the heat is exiting the system and Endothermic is just the opposite so it absorbs the heat or heat is put into the system

Exothermic reminds me of exit and the first 2 letter in endothermic reminds me of in (enter).