endothermic vs exothermic

[Natalie Flores 1F]

The relatively simple concept of endothermic vs exothermic is confusing me and not sticking with me. From what I remember endothermic absorbs heat which makes the surroundings cold while exothermic releases heat and makes the surroundings hot but how do I know if a reaction is endo or exothermic? Also, generally do forming bonds require energy (endothermic) while breaking bonds release energy (exothermic) or does that depend too? If someone could briefly summarize this information because I tend to confuse myself. Thanks!

[Maia V 1L]

Endothermic is when heat is added to the equation ( the reaction requires heat), and exothermic is when heat is released. Breaking bonds releases heat and forming bonds requires heat.

[Natasha]

Yes, forming bonds does require energy and this is an example of an endothermic process. And breaking bonds is an example of an exothermic process since it releases energy.

[Vikram Sharma]

So basically in every chemical reaction, old bonds (reactants) are being broken (energy is required) and new bonds (products) are being formed (energy is released). If the total energy released by forming products is greater than the total energy required to break the reactants in a given chemical reaction, then the reaction is exothermic because there is a net release of energy. If the total energy released by forming products is less than the total energy required to break the reactants, then the reaction would be endothermic because there is a net uptake of energy from the surroundings.

[105707059]

Another way to think of it is that endothermic reactions absorb energy from the surroundings, often causing the surroundings to cool, whereas exothermic reactions release energy to the surroundings which often causes the surroundings to heat up.

[Brandon Yu]

If heat is used up in the equation (heat is a reactant), then the reaction is endothermic because heat is required for the reaction to begin. As for bonds, breaking bonds ALWAYS requires some energy and forming bonds releases energy.

[N Kanuri 2E]

Your examples are correct! You can distinguish between endo- and exothermic reactions by looking at the delta H of the reaction. If it is negative, then the reaction is exothermic. If delta H is positive, the reaction is endothermic.

[Cindy Vo 3E]

Ednothermic and exothermic are just how you described. You can find out if a reaction is endothermic if delta H is positive. Exothermic is if delta H is negative. Also, if heat requires heat, it is a reactant so endothermic. If heat releases heat, it is a product, so exothermic.

[Amy Jordan 2A]

Hi, exothermic is releasing energy, and endothermic is absorbing energy. In an endothermic reaction, the energy to break reactant bonds is greater than the energy released and it's the opposite for exothermic reactions. Hope this help!

[Allen Mayo 1E]

Endothermic reactions absorbs energy and exothermic reactions release it. Like it was said in another post in this forum, if net energy in the reactions leans toward forming bonds, then the reaction is endothermic because it uses more energy to form bonds than to break them. This is vice-versa.

[JasmineReyes-2K]

Hi!,
An exothermic process releases heat, causing the temperature of the immediate surroundings to rise while an endothermic process absorbs heat and cools the surroundings.

[Kimberly_martinez2I]

An endothermic reaction absorbs heat and delta H is positive. An exothermic reaction is one that releases heat so delta H is negative.

[Natalie Coughlin 1I]

A reaction that is endothermic requires an input of energy, while a reaction that is exothermic releases energy. When you think about this in terms of bonds, forming a bond is exothermic because it releases energy, while breaking a bond is endothermic because it requires energy.

[Amy Wong 2F]

An endothermic reaction requires energy to proceed, and an exothermic reaction releases energy when it proceeds.

[Alexandra Gill]

endothermic= gaining heat (forming bonds)
exothermic=releasing heat (breaking bonds)

[Naman Jain 3F]

An endothermic reaction requires absorbs energy from the surroundings, thus cooling the surroundings. Breaking bonds is an endothermic process as it requires energy. An exothermic reaction releases energy to the surroundings, thus heating the surroundings. Forming bonds is an exothermic process as it releases energy.

[Jessica Sun 2I]

Endothermic reactions break bonds and require heat and exothermic reactions form new bonds and gives off heat.

[Jonathan Shyu 3L]

Endothermic means that the products have a higher "heat" than reactants, thus adding heat or increasing temperature would favor products because it has higher "heat." This also means that endothermic reactions take in heat for the reaction because products require it, and so the surrounding temperature drops. Exothermic means that the products have a lower "heat" than reactants, so removing heat or decreasing temp would favor products and build more reactants. Exothermic also means that the reaction is releasing heat to produce products, so the surrounding would get warmer.

[JohnathanH_1H]

Endothermic reactions need heat making heat an input in the equation where endothermic reactions release heat making it an output in the equation

[eve444]

Endothermic:
- requires energy
- bond release
- K increases with temp

Exothermic:
- releases energy
- bond formation
- K decreases with temp

[Omar Alkhalili 1J]

hello! endothermic reactions absorb energy and exothermic reactions release energy. Bonds are broken in endothermic reactions and bonds are formed in exothermic reactions.

[Isamar Aburto Paniagua 2K]

Endo = Inside thus endothermic reactions pull in heat
Exo - Outside thus exothermic reactions release heat.

So in the case of bonds , forming them would be considered ENDOthermic as it requires energy to do so and breaking bonds would be considered EXOthermic as it is releasing energy.

[305749341]

An exothermic reaction releases heat into the surroundings which makes the surroundings warmer. That means the products have lower enthalpy than the reactants. An endothermic reaction absorbs heat. This makes the surroundings cooler. The products have higher enthalpy than the reactants.

[taline krumian 1L]

in an endothermic reaction, the system gains heat & forms bonds
in an exothermic reaction, the system releases heat & breaks bonds

[Sophia Manos 1F]

Exothermic reactions release heat into the surroundings while endothermic reactions absorb heat. Endothermic reactions break bonds while exothermic reactions form new bonds.

[505749458]

BE CAREFUL this is easy to mess up! I like to think about it as the initial and final energy levels that the molecule/atom will be at. Remember atoms/molecules form bonds because they are more stable in these compounds, and more stability means lower potential energy. So when an atom/molecule forms a bond, they stabilize and reach a lower energy level. Lowering the energy level means they had to have released energy, so FORMING BONDS is EXOTHERMIC! Bonds don't like to be broken, so you have to put in a lot of energy to break them, and the lonely sets of individual atoms/molecules end up at a higher potential energy than what they were at initially, so BREAKING BONDS is ENDOTHERMIC!

[Shannon Clark 1F]

Endothermic is when heat is absorbed, and exothermic is when heat is released!

A way of thinking that helps me remember this is that you can think of the prefix "exo-" sounding like "exit" so exothermic is heat exiting the reaction!

[Richie Ngoy]

So if you look at the chemical equation, if heat (in the reactants) is used in the equation, then the reaction is endothermic. Other examples includes whenever you see the breaking of bonds because energy is required to break and form bonds.

[Jinhee Lee 3B]

Hello! An endothermic reaction absorbs heat, making the surrounding cold. An exothermic reaction releases heat after the reaction, making the surrounding hot. An easy way to remember this is endo=inside and exo=outside, referring to the direction heat/energy goes towards. In order for bonds to break, it needs energy to split them apart, making it an endothermic reaction. When bonds form, the ending result is a release of energy, making it an exothermic reaction.

[Augustin Kelly 3E]

That makes it a lot easier to remember. So
Exo: Gives off heat, and forms bonds
Endo: Absorbs heat, and breaks bonds, right?
Thank you!

[505780104]

How do we know the direction of the reaction when given an equation? Do we follow which side heat is on in an equation? Why does K go down when the reaction is exothermic? I understand that cooling is present and that is how products are formed, however I do not understand why the equilibrium constant changes. Vise versa, why does the K go up when the reaction is endothermic? Any explanation would help, the diagrams make sense as to why heat or cooling is necessary but I do not understand why the K is changing in both of these scenarios.

[Kaylee Cheng 3E]

As many have mentioned, endothermic reactions occur when energy is absorb, while the exothermic reaction describes a release of energy. In a chemical equation, exothermic energy will appear as an additional heat to the product because it’s energy is given off. And exothermic reactions will be seen on the side of the reactant as it is being absorbed by the reaction.

[Jason T 1I]

In Endothermic reactions energy is gained by forming bonds and in exothermic reactions energy is released by breaking bonds.

[jenna koerner 2E]

Endothermic reactions absorb energy. For example, boiling water is endothermic and requires heating water in order to make it boil. The breaking of bonds is also endothermic, where it requires energy to break the bond. On the other hand, exothermic reactions release energy. If an exothermic reaction were to occur in a beaker, you would be able to feel the beaker warm up, thus the energy being released from the reaction. So, the formation of bonds is exothermic because it releases energy when it is formed.

[Andrew Greenberg 2D]

The relatively simple concept of endothermic vs exothermic is confusing me and not sticking with me. From what I remember endothermic absorbs heat which makes the surroundings cold while exothermic releases heat and makes the surroundings hot but how do I know if a reaction is endo or exothermic? Also, generally do forming bonds require energy (endothermic) while breaking bonds release energy (exothermic) or does that depend too? If someone could briefly summarize this information because I tend to confuse myself. Thanks!

Endothermic is going to have a positive enthalpy meaning it requires energy. This also means the reactants will have more energy than the products. Exothermic is going to have a negative enthalpy meaning it releases energy. This means the products have more energy than the reactants. I believe that the process of breaking a bond is endothermic and the process of forming a bond is exothermic but I am not positive.

[VictoriaPietrusiew2H]

Exothermic
- gives off heat
- negative delta H
- reactants have a higher enthalpy
- reactant forms if system is cooled because reactants have lower enthalpy
- occurs when bonds form because energy is released when bonds form (bonds want to be formed, since this increases stability of an element.

Endothermic
- requires heat
- positive delta H
- products have a higher enthalpy
- occurs when bonds break because energy is required to break a bond.

[Bella Valente 2K]

One way to tell is by looking at enthalpy, if it is negative then there is a release of energy and the reaction is exothermic, conversely if enthalpy is positive then energy needs to be added and the reaction is endothermic

[Viviana Hsiao 1G]

endothermic reactions absorb heat, cooling the surroundings. exothermic reactions release heat, warming the surroundings. you can tell if a reaction is endothermic or exothermic if the enthalpy value is positive or negative, respectively. forming bonds releases energy (exothermic), while breaking bonds requires energy (endothermic).

[Angie Tan 2L]

Endothermic is when a reaction requires heat and has a positive change in enthalpy since the products hold more energy than the reactants. Breaking bonds require heat and are endothermic. Exothermic is when a reaction releases heat and has a negative change in enthalpy. Forming bonds releases energy and is exothermic.

[Octavio Santana 2H]

Endothermic can be identified when written in the reactants (because reaction requires heat), whereas exothermic can be identified when written in the products (because reaction releases heat)! Also, you are correct, forming bonds requires energy, and breaking bonds releases energy!

[HenrikZhang2K]

endothermic is when a reaction requires heat, whereas exothermic means the reaction releases heat.

[Nayuki_2J]

You can tell whether the reaction is endo or exothermic by checking the net enthalpy, which we know we can calculate using one of the three methods (Hess's, bond enthalpy, and standard enthalpy). If the enthalpy is negative the reaction is exothermic and if enthalpy is positive the reaction is endothermic. Since you already know the relationship between heat and exo/endothermic, it might be helpful if you memorized it as enthalpy being the sum of the internal energy and pressure*volume, so whenever heat energy leaves the system there will be less energy within the system and thus negative enthalpy for exothermic reactions and vice versa. And yes, as far as I know, breaking bonds will always require energy (endothermic) and making bonds will always release energy (exothermic).

[Reese R 1E]

Exothermic means that the enthalpy of the products is less than the enthalpy of the reactants, resulting in the reaction giving off heat and a negative delta H (H_final - H_initial = -value). Endothermic means that the enthalpy of the products is greater than the enthalpy of the reactants, resulting in the reaction requiring heat and a positive delta H ( H_final - H_inital = + value).

[Julianne_Sue_3A]

We can also see the differences between endothermic and exothermic reactions via an energy diagram. By comparing how much energy the products and reactants contain, we can deduce if the reaction gains or releases energy. The energy level of products will be higher than the energy level of reactants in an endergonic reaction; likewise, the energy level of reactants will be higher than the energy level of products in an exergonic reaction. This is due to the gain/loss of energy depending on what type of reaction it is.

[Elliana_Tsang_1L]

An endothermic reaction requires heat to be put in, with the products having a higher energy than the reactants, so delta H is positive. An exothermic reaction releases energy, with the reactants having a higher energy than the products, so delta H is negative. To answer your second question, breaking bonds is always exothermic and making bonds is always endothermic. In a bond, the atoms have intramolecular forces which keep them together. There is a shared electron pair in the case of covalent bonds or electrostatic forces in the case of ionic bonds. It requires energy to be put in to overcome these forces and separate the atoms. Inversely, you must put energy in to create a bond that reaches equilibrium bond length.

[Jonathan Choe 3D]

Endothermic reaction is when heat is added to the equation, and exothermic is when heat is released. Breaking bonds releases heat and forming bonds needs heat.

[Sriya Chilla 2E]

Hi Natalie!

You can also perform an experiment to test whether a reaction is endo or exothermic. In the example from class, we used the reaction of 2NO2 <--> N2O4. NO2 is typically amber, while N2O4 is typically clear. We can cool the reaction down and observe whether the tube becomes amber or clear, indicating whether the reaction proceeds to the reactants or products. In this case, we observe that cooling the reaction leads the reaction tube to become clear (proceeds to products). Therefore, we know the reaction is exothermic.