## Endothermic v. Exothermic

Samantha Lee 1A
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### Endothermic v. Exothermic

In class today, we learned about endothermic reactions in depth (vaporization, fusion, sublimation) and that the have a positive delta H. Will they ALWAYS have a positive delta H? Does that mean that exothermic reactions will ALWAYS have a negative delta H?

Are there any exceptions to this rule?

Andrew Wang 1C
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### Re: Endothermic v. Exothermic

I assume that's the case, since the sign of delta H is kind of "built in" to the definitions of endothermic and exothermic. Negative delta H means heat is released, so it's exothermic, while positive means heat is absorbed which is endothermic.

Chem_Mod
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### Re: Endothermic v. Exothermic

Yes, endothermic reactions will always have a positive delta H, and exothermic reactions will always have a negative delta H.

Frankie Mele 3J
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### Re: Endothermic v. Exothermic

I think that endothermic reactions will always have a positive change in enthalpy because in order for the reaction to be classified as endothermic in the first place, heat must be absorbed.

Rahul Sobti 1E
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### Re: Endothermic v. Exothermic

Yes. Endothermic reactions will always have a positive Delta H as they are absorbing energy so the products will have more energy than the reactants. Same with exothermic reactions, Delta H will always be negative because the products will have less energy than the reactants.

JonathanSung_2G
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### Re: Endothermic v. Exothermic

Whether heat is absorbed or released determines if the reaction is endothermic or exothermic. A reaction that absorbs heat will be endothermic with a positive delta H.

Libby Dillon - 1A
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### Re: Endothermic v. Exothermic

Yes, I believe the value of delta H (positive or negative) is the determining factor of whether something is endothermic or exothermic. In an endothermic reaction, heat is required, so delta H will always be positive. In an exothermic reaction, heat is released, so delta H will always be negative.

Emmeline Phu 1G
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### Re: Endothermic v. Exothermic

Hi! Yes, endothermic reactions will always have a positive enthalpy indicating the absorption of heat whereas exothermic reactions will always have a negative enthalpy indicating the release of heat. Hope this helps! :)

KhanTran3K
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### Re: Endothermic v. Exothermic

I do not believe that there are any exceptions to the rule, and you are correct. This is due to the nature of "delta H" itself. Delta H is the change in enthalpy. So, when you have a positive value, it tells us that the enthalpy in the products is higher than the reactants, which mean it requires energy or heat to get it to change. With this, the opposite is true for exothermic reactions, or negative delta H values.

My-Lan Le 1L
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### Re: Endothermic v. Exothermic

Yes, I think those statements should always be true. You can tell if a reaction is exothermic or endothermic by calculating its delta H. If it is positive, the reaction is endothermic, and if it is negative, the reaction is exothermic. This statement would make sense because H is enthalpy which is the amount of heat released or absorbed, which is basically also showing whether the reaction is exothermic or endothermic in the process.

Ria Nawathe 1C
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### Re: Endothermic v. Exothermic

Just a side note: fusion, vaporization, and sublimation aren't really reactions because there aren't any chemical bonds being broken, they're considered phase changes and are physical changes because it's just the intermolecular attractions that are being overcome.

DMaya_2G
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### Re: Endothermic v. Exothermic

Endothermic reactions will have a positive delta H because the reaction requires heat. In contrast, exothermic reactions will have a negative delta H because the reaction gives a net release of heat.

Inderpal Singh 2L
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### Re: Endothermic v. Exothermic

I do not believe there are any exceptions to this rule. Exothermic means releasing heat, so a positive delta H would not be possible. The vice versa applies to endothermic, which takes in heat, so a negative delta H would not be possible.

Joseph_Armani_3K
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### Re: Endothermic v. Exothermic

I believe so; endothermic reactions will always have a positive enthalpy and exothermic reactions will always have a negative enthalpy.

Karl Yost 1L
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### Re: Endothermic v. Exothermic

Endothermic reactions always have a +ve delta H, while exothermic reactions always have a -ve delta H.

I don't believe that there are any exceptions to this rule.

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### Re: Endothermic v. Exothermic

Yes if you are losing heat from the system,endothermic, the delta h will be negative

Vanshika Bhushan 1A
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### Re: Endothermic v. Exothermic

An endothermic process has a positive delta H because the system is gaining heat. An exothermic process has a negative delta H because the system is losing heat.

Moura Girgis 1F
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### Re: Endothermic v. Exothermic

That's right, since exothermic reactions will be losing heat, that means that the delta h must be negative.

Ariel Guan 1H
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### Re: Endothermic v. Exothermic

yea, endothermic rxns will always have a positive delta H, and exothermic rxns will always have a negative delta H

Lorraine Jiang 2C
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### Re: Endothermic v. Exothermic

Yes, that is correct! Exothermic reactions always have a negative delta H, and an endothermic reaction will always have a positive delta H.

Hope it helps!

Olivia Smith 2E
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### Re: Endothermic v. Exothermic

Yes exothermic will always have a delta - H and endothermic will always have a positive delta H as that is the definition. negative delta H means that the system is releasing energy and positive delta H means

Pierce Newman 1A
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### Re: Endothermic v. Exothermic

Endothermic reactions always have net positive delta H and exothermic reations always have net negative delta H, but for differing reactions you could have different "paths". For example if you burn glucose in the lab there is one exothermic step, but in the body there are many, with some exothermic and some endothermic(energy investment) steps. But enthalpy is a state property, meaning both reactions have overall net negative delta H and they are both considered to be favorable or exothermic.

Samudrala_Vaishnavi 3A
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### Re: Endothermic v. Exothermic

Yes, I would say so in my opinion but I don't know if there any exceptions out there. To be clear, sublimation, vaporization, and fusion all are endothermic to begin with and you have to add heat to the system for there to be a phase change from ice to steam, that is why they all have positive delta H values. Since the change in enthalpy basically corresponds to the absorption of heat by a system, and exothermic reactions release heat, there has to be a negative delta H value.

Claudia_Danysh_2B
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### Re: Endothermic v. Exothermic

Yes, a negative delta H is always going to be exothermic because it released heat in the process, making enthalpy a negative value. Additionally, a positive delta H value will always be endothermic because it required heat in the process!

aashmi_agrawal_3d
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### Re: Endothermic v. Exothermic

Yes, because a positive delta H is absorbing heat and a negative delta H is releasing heat.

Yeonjoo Kim 2B
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### Re: Endothermic v. Exothermic

Exothermic reactions will always be negative because the total energy of the products is less than that of the reactants which is why energy gets released.

Joshua Swift
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### Re: Endothermic v. Exothermic

Endothermic reactions will always have a +$\Delta$H and exothermic reactions will have a -$\Delta$H. if heat is showed in the reaction on the reactants side it is endothermic and if it is present on the products side it is an exothermic reaction.

Jonathan Malau 1F
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### Re: Endothermic v. Exothermic

Yes, endothermic reactions will always have a positive delta H (meaning that it absorbs energy), and exothermic reactions will always have a negative delta H (as it releases energy).

Alen Huang 2G
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### Re: Endothermic v. Exothermic

Yes! Endothermic reactions will always have a positive enthalpy change and exothermic reactions will always have a negative enthalpy change.

Aayushi Jani 3A
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### Re: Endothermic v. Exothermic

Yes, endothermic reactions have a positive delta H since they require energy while exothermic reactions have a negative delta H since they release energy.

Jiapeng Han 1C
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### Re: Endothermic v. Exothermic

I think at least according to the definition, endothermic reaction has positive H while exothermic reaction has negative H.

Jiayi Wu 3J
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### Re: Endothermic v. Exothermic

I think so, if the sign changes, their property would change too, so endothermic reaction would be exothermic

Margaret Xu 3C
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### Re: Endothermic v. Exothermic

I believe you're right! When the enthalpy is positive, we can think of the endothermic reaction as heat going into the system, so the increase in heat is represented with +. When the enthalpy is negative, the endothermic reaction releases--or loses-- heat, so the decrease in heat in the overall system is -.

Devin Patel 2D
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### Re: Endothermic v. Exothermic

An endothermic reaction will always have a positive delta H because, for a reaction to endothermic, it absorbs heat. An exothermic reaction will always be a negative delta H because, for a reaction to be exothermic, it gives off heat.

Brian Nguyen 2I
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### Re: Endothermic v. Exothermic

Yes, this is definitely true. Exothermic reactions are always labeled by a negative delta H, whereas endothermic reactions are always labeled by a positive delta H. This is due to how exothermic reactions release heat, whereas endothermic reactions absorb heat.

Alisa Nagashima 1B
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### Re: Endothermic v. Exothermic

Yes, endothermic reactions absorb heat hence the negative delta H. Exothermic reactions release heat hence the positive delta H.

Javier Perez M 1H
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### Re: Endothermic v. Exothermic

Definitely, use the delta H to determine whether is endothermic or exothermic.

Akemi Karamitsos 1E
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### Re: Endothermic v. Exothermic

Delta H represents the change in enthalpy, which is the total heat content of a system. So yes, the positive or negative sign of delta H should be used to determine whether a reaction is endothermic or exothermic. When it is less than zero, this means that heat has been released from the system, indicating an exothermic reaction. Similarly, when it is greater than zero, heat has been absorbed, indicating an endothermic reaction.

Ziyan Peng 3A
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### Re: Endothermic v. Exothermic

Yes. You can also make sense of this by thinking about enthalpy being a state property. As long as the amount of heat is greater than the system began with, it is definitely endothermic, and vice versa for exothermic reactions.

Kat Stahl 2K
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### Re: Endothermic v. Exothermic

I don't think there are any exceptions to this rule! Exothermic reactions will have a negative delta H and endothermic reactions will have a positive delta H.

sophia kosturos 2B
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### Re: Endothermic v. Exothermic

that is correct, endothermic reactions will always have positive delta H values because they absorb heat and exothermic reactions will always have negative delta H values because they release heat.

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### Re: Endothermic v. Exothermic

I do think that these are always true because the definition of endothermic is that it requires heat (and exothermic releases heat). This probably means that endothermic reactions will always have a positive delta H and exothermic reactions will always have a negative delta H. I'm not sure if there are any exceptions, but I don't think we will need to know that for this class.

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### Re: Endothermic v. Exothermic

Yes, by definition an endothermic reaction requires heat (positive H) whereas an exothermic reaction expels heat (negative H

Hana Sigsbee 3B
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### Re: Endothermic v. Exothermic

Yes, endothermic reactions will always have a positive delta H because the change is positive and exothermic reactions will always have a negative delta H because the change is negative.

Luveia Pangilinan 1A
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### Re: Endothermic v. Exothermic

Yes that is right. I don't think there are any exceptions that can bend the rule for it but I'm pretty positive that's the case

David Y
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### Re: Endothermic v. Exothermic

Endothermic always has a positive delta (change in) H

Mingzi Yang 1E
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### Re: Endothermic v. Exothermic

Endothermic reactions have a positive delta H and exothermic reactions have a negative delta H.

Chance Herbert 3A
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### Re: Endothermic v. Exothermic

Yes! Endothermic reactions will always have a positive delta H as the system absorbs energy while exothermic reactions release energy from the system, resulting in a negative delta H

Isabella Cortes 2H
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### Re: Endothermic v. Exothermic

yes!! endothermic reactions will always have a positive delta H and exothermic reactions will always have a negative delta H

Abhinav Behl 3G
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### Re: Endothermic v. Exothermic

Yep, endothermic reactions will always have a positive delta H, because this type of reaction takes in heat, thus it would have a positive change in enthalpy. On the other hand, exothermic reactions will have a negative delta H because you lose heat while the reaction is taking place, thus resulting in a negative change in enthalpy.

Edison Tham 3D
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### Re: Endothermic v. Exothermic

Yes! Any endothermic reaction would have a positive ∆H value and any exothermic reaction would have a negative ∆H value.

Ximeng Guo 2K
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### Re: Endothermic v. Exothermic

Exothermic reactions have a negative delta H and endothermic reactions have a positive delta H.

Hannah Lechtzin 1K
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### Re: Endothermic v. Exothermic

Yes, endothermic reactions will always have a positive delta H because it indicates that the reaction is taking in heat, while exothermic reactions will always have a negative delta H because that indicates that the reaction is giving off heat.

AJForte-2C
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### Re: Endothermic v. Exothermic

you can think of an endothermic reaction as the system you're viewing "gaining" enthalpy or heat. This would mean that your △H is positive.

Diana Aguilar 3H
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### Re: Endothermic v. Exothermic

Yes, like others have said, endothermic reactions will always have a positive delta H and exothermic reactions will always have a negative delta H

Abraham De Luna
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### Re: Endothermic v. Exothermic

Endothermic reactions will always have a positive delta H whereas an exothermic reaction will always have a negative delta H.

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### Re: Endothermic v. Exothermic

Yeah exothermic reactions also have a negative delta H and endothermic reactions always have a positive delta H because of the way exothermic reactions are defined as releasing energy while endothermic reactions are defined as absorbing energy.

Constance Newell
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### Re: Endothermic v. Exothermic

Exothermic reactions have a negative delta H and endothermic reactions have a positive delta H

Laura 3l
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### Re: Endothermic v. Exothermic

Endothermic will always be a positive enthalpy value and exothermic will always be a negative enthalpy value.

Nicoli Peiris 1B
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### Re: Endothermic v. Exothermic

Yes endothermic reactions are always positive and exothermic reactions are always negative.

Katie Le 3K
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### Re: Endothermic v. Exothermic

There are no exceptions to this rule

Cora Chun 2D
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### Re: Endothermic v. Exothermic

Yes, I believe this is always the case. Endothermic reactions have a positive delta H, and exothermic reactions have a negative delta H. Vaporization and fusion are always endothermic (because you need to put in heat to get liquids to their gas state and solids to their liquid state), and condensation of gas into liquid and liquid to solid is exothermic.

jessicasilverstein1F
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### Re: Endothermic v. Exothermic

Yes, this is true. Endothermic reactions will always have a + delta H, and exothermic reactions will always have a - delta H, this is the case for all

reyvalui_3g
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### Re: Endothermic v. Exothermic

I do not believe that there are any exceptions to this rule.

Lorena_Morales_1K
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### Re: Endothermic v. Exothermic

Why is bond formation exothermic again?

Kayko Lee 1C
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### Re: Endothermic v. Exothermic

Lorena_Morales_1K wrote:Why is bond formation exothermic again?

I believe it's exothermic because the system loses energy to form the bonds and since there's a decrease in energy, the energy is lost as heat and makes the process exothermic

Taylor Newville 1C
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### Re: Endothermic v. Exothermic

The definition of delta H is the change in enthalpy of a system. The definition of exothermic is that heat is released during a reaction and the enthalpy of the system decreases (which can only ever be represented by a negative delta H). The opposite is true of endothermic. So, you are right and there are no exceptions.

Taylor Newville 1C
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### Re: Endothermic v. Exothermic

Lorena_Morales_1K wrote:Why is bond formation exothermic again?

Bonded atoms/molecules are more stable. Unbound atoms require energy to keep them apart which is released when they form a bond, making bond formation exothermic.

Chinmayi Mutyala 3H
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### Re: Endothermic v. Exothermic

Yes, endothermic will be positive since it is absorbing heat and exothermic will be negative since it is releasing heat.

Alex Benson
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### Re: Endothermic v. Exothermic

Yes that will always be the case! I have not heard Lavelle or anybody else speak to any exceptions to the rule!

Morgan Gee 3B
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### Re: Endothermic v. Exothermic

Endothermic reactions will always have a positive deltaH because they require energy. On the other hand, exothermic reactions will always have a negative deltaH because they release energy.

Shana Patel 1C
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### Re: Endothermic v. Exothermic

Exothermic reactions will always be negative because the total energy of the products is less than that of the reactants which is why energy gets released.

Julianna_flores3E
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### Re: Endothermic v. Exothermic

Endothermic reactions will always be positive and exothermic reactions will always be negative.

Emma Strassner 1J
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### Re: Endothermic v. Exothermic

Endothermic reactions will always be positive because they require heat to occur, and exothermic reactions will always be negative because they release heat and therefore lose energy.

Rose_Malki_3G
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### Re: Endothermic v. Exothermic

Yes endothermic reactions will always have a positive enthalpy and exothermic reactions will always have a negative enthalpy/delta H

Charmaine Ng 2D
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### Re: Endothermic v. Exothermic

Yep, endothermic will always be positive, since an endothermic reaction always takes in energy, while exothermic will always be releasing, and therefore always negative :))

Aliya Roserie 3I
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### Re: Endothermic v. Exothermic

Yes! You are correct. I haven't heard of any exceptions to this rule.

apurva-3E
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### Re: Endothermic v. Exothermic

Yes, endothermic reactions will always have a positive deltaH values.

Muskaan Abdul-Sattar
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### Re: Endothermic v. Exothermic

Yes, you'll find that exothermic reactions will always have a negative delta H while endothermic reactions will always have a positive delta H. This is due to the fact that heat is either being released or absorbed.

rhettfarmer-3H
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### Re: Endothermic v. Exothermic

yes, I think it is common that positive H is always endothermic and exothermic is always negative. There is no real expectation of these rules because H will always change based on the environment and changes.

Karina Grover 1A
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### Re: Endothermic v. Exothermic

Endothermic reactions are characterized by their positive "delta H" values. In endothermic reactions, temperature/heat can be treated as a "reactant." Thus, when temperature is increased, the reaction will shift to the right, and when temperature is decreased, the reaction will shift to the left.

Exothermic reactions are characterized by their negative "delta H" values. In exothermic reactions, temperature/heat can be treated as a "product." Thus, when temperature is increased, the reaction will shift to the left, and when temperature is decreased, the reaction will shift to the right.

MCalcagnie_ 1D
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### Re: Endothermic v. Exothermic

I am pretty sure because of the nature of exothermic and endothermic reactions, exothermic will always be negative and endothermic will always be positive. Exothermic is releasing heat, so the object or substance of interest would be losing heat, with a -delta H. Endothermic is requiring heat, so the object or substance of interest would be gaining heart, with a +delta H.

Presley Gao 2C
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### Re: Endothermic v. Exothermic

Yes, endothermic reactions will always have a positive delta H, and yes, exothermic reactions will always have a negative delta H. There are no exceptions to this rule.

Bryan Le 2K
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### Re: Endothermic v. Exothermic

Delta H is positive when the reaction is endothermic because heat is absorbed while delta H is negative when the reaction is exothermic because heat is released.

Kelly Ha 1K
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### Re: Endothermic v. Exothermic

Endothermic reactions have a positive delta H because the system is absorbing heat from the surroundings. Exothermic reactions have negative delta H because the system is releasing heat into the surroundings.

Annie Liang 3D
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### Re: Endothermic v. Exothermic

Yes, endothermic reactions always have positive delta H values while exothermic reactions will always have a negative delta H value.

Rachel Kho Disc 2G
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### Re: Endothermic v. Exothermic

I'm pretty sure that there will be no exceptions to the fact that delta H is positive and negative for endothermic and exothermic reactions, respectively. Other things to keep in mind when differentiation between the two include:

Endothermic
- energy absorbed
- bonds broken
- strong reactant bonds

Exothermic
- energy released
- bonds formed
- strong product bonds

joshtully
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### Re: Endothermic v. Exothermic

Endothermic reactions has a positive delta H value while exothermic has negative.

RyanKopeikin_2I
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### Re: Endothermic v. Exothermic

Exothermic reactions will always have negative delta H because heat is being released, which is denoted with a negative sign. Endothermic reactions will always have positive delta H because heat is being absorbed, which is denoted with a plus sign.

Carly_Lipschitz_3H
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### Re: Endothermic v. Exothermic

Yes, you're correct. Exothermic reactions will always have a negative delta H, while endothermic reactions will always have a positive delta H. Endothermic reactions take up energy, making their delta H positive while exothermic reactions give away energy to its surroundings, making their delta H negative.

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### Re: Endothermic v. Exothermic

Exothermic reactions are a release in heat and, thus, they have a negative value associated with them. An absorption in energy/heat is an endothermic process, and, therefore, it will always be positive.

Vivian_Le_1L
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### Re: Endothermic v. Exothermic

Endothermic reactions will always have a positive delta H, because they are taking in heat/energy. Exothermic reactions will always have a negative delta H, because they are releasing heat/energy.

Ryan_Kien_1L
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### Re: Endothermic v. Exothermic

Yes, by definition, I believe positive delta H is endothermic because it's a gain in energy, meaning a positive delta H.

Jose Miguel Conste 3H
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### Re: Endothermic v. Exothermic

That will always be the case as when you have to input energy, delta H has to be positive

Lauren Mungo 1K
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### Re: Endothermic v. Exothermic

Yes exothermic reaction always have a negative delta H and endothermic reactions have a positive delta H

Karen Zheng_2K
Posts: 88
Joined: Fri Sep 29, 2017 7:04 am

### Re: Endothermic v. Exothermic

Endo = (+)delta H, and Exo = (-)delta H

John_Tran_3J
Posts: 97
Joined: Wed Sep 30, 2020 9:58 pm

### Re: Endothermic v. Exothermic

Regarding phases change, when a solid becomes to liquid, heat is NEEDED to melt the solid.. also known as endothermic

Karen Elrayes 1L
Posts: 90
Joined: Wed Sep 30, 2020 9:45 pm

### Re: Endothermic v. Exothermic

Endothermic means energy went into the system which means delta H increased so it has to be positive. And the opposite is also true.

IshanModiDis2L
Posts: 95
Joined: Wed Sep 30, 2020 9:49 pm

### Re: Endothermic v. Exothermic

Yes they will always act this way; exothermic reactions will always be losing heat, meaning that the delta h must be negative and endothermic reactions will always be gaining heat with a positive delta h

rhettfarmer-3H
Posts: 101
Joined: Wed Sep 30, 2020 9:59 pm

### Re: Endothermic v. Exothermic

Yes, exothermic reactions will always have a negative H. However, if the Recants acclimate then it can become spontaneous which I don't know if that shows more about h or the G.