exothermic and endothermic reactions. I honestly dont get it at all. I looked it up and still couldn’t find a clear answer for me.


exothermic and endothermic reactions. I honestly dont get it at all. I looked it up and still couldn’t find a clear answer for me.

In: Chemistry

Exo/thermic: exo = out or outer / thermic = heat

A reaction that releases heat.

Endo/thermic: endo = within or innter / thermic = heat

A reaction that absorbs heat.

Exothermic reactions produce heat. Endothermic reactions absorb heat. Some things absorb heat as they are combined in order to make the final product of the mixture some have extra energy that is released as heat when they are combined.

Exothermic reactions will release energy when they occur. Energy is released by the reaction in the form of heat. An example of this is something burning, or an explosion.

Endothermic reactions absorb and require energy (heat) in order to occur. A simple example of an endothermic reaction is melting an ice cube to form water. The ice has to ‘steal’ heat from the surronding air in order to turn into water. These reactions can sometimes feel cold to the touch because of them absorbing heat from the environment.

Hope that helps!

Don’t know if you’ve seen this;

Dr. Schambaugh, of the University of Oklahoma School of Chemical Engineering, Final Exam question for May of 1997. Dr. Schambaugh is known for asking questions such as, “why do airplanes fly?” on his final exams. His one and only final exam question in May 1997 for his Momentum, Heat and Mass Transfer II class was: “Is hell exothermic or endothermic? Support your answer with proof.”

Most of the students wrote proofs of their beliefs using Boyle’s Law or some variant. One student, however, wrote the following:

>”First, We postulate that if souls exist, then they must have some mass. If they do, then a mole of souls can also have a mass. So, at what rate are souls moving into hell and at what rate are souls leaving? I think we can safely assume that once a soul gets to hell, it will not leave.
Therefore, no souls are leaving. As for souls entering hell, let’s look at the different religions that exist in the world today. Some of these religions state that if you are not a member of their religion, then you will go to hell. Since there are more than one of these religions and people do not belong to more than one religion, we can project that all people and souls go to hell. With birth and death rates as they are, we can expect the number of souls in hell to increase exponentially.
Now, we look at the rate of change in volume in hell. Boyle’s Law states that in order for the temperature and pressure in hell to stay the same, the ratio of the mass of souls and volume needs to stay constant.
>Two options exist:
If hell is expanding at a slower rate than the rate at which souls enter hell, then the temperature and pressure in hell will increase until all hell breaks loose.
If hell is expanding at a rate faster than the increase of souls in hell, then the temperature and pressure will drop until hell freezes over.
>So which is it? If we accept the quote given to me by Theresa Manyan during Freshman year, “that it will be a cold night in hell before I sleep with you” and take into account the fact that I still have NOT succeeded in having sexual relations with her, then Option 2 cannot be true…Thus, hell is exothermic.”

The student, Tim Graham, got the only A.

Endothermic: for instance photosynthesis: plants recompose carbon dioxde and water into living matter and oxygen. But the process requires energy (=sun light or artificial light).

Exothermic: burning coal + oxygen produces carbon dioxyde and heat (=energy). Here you don’t require energy, you produce it.

Endothermic reactions have an energy deficit when reaction occurs. This needed energy is typically stolen from heat in the environment.

Exothermic reactions have an energy excess when the reaction occurs. This energy is typically expended as heat.

Why is there a deficit or excess? When we break electron bonds, it creates energy. And vice versa, creating electron bonds cost energy. Not all bonds are created equal so different bonds will have different energies relating to it. These bonds are typically characterizes by the molecules bonding. (H-H, C-H,C-C, etc)

When you have a reaction, bonds are broken and remade – for example, when you burn wood, what is happening is the fuel is reacting with oxygen, and in breaking the bonds of the fuel and combining carbon with the oxygen in the air to make carbon dioxide, more energy is being released than is being put in – so this is an exothermic reaction, fire.

An opposite example is dissolving ammonium chloride into water, in this reaction you have to put more energy into the reaction to dissolve the ammonium chloride, this energy is taken from the surroundings, the heat is absorbed and the reaction feels colder, it is endothermic.

So in a reaction that puts out more energy, usually as heat, but also sometimes light, is exothermic.

In a reaction that takes in more energy, and therefore makes its surrounding environment cold, it is endothermic