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Exothermic and Endothermic Reactions

Last updated date: 23rd Jul 2024
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What is Endothermic Reaction?

An endothermic process is any process or reaction which absorbs or assimilates power or energy from its environment, for the most part as heat. It might be a compound process, for example, dissolving salt in water, or essentially the liquefying of ice shapes. The term was instituted by Marcellin Berthelot from the Greek root’s endo-, got from "Endon" signifying "inside", and the root "therm", signifying "hot" or "warm" as in a reaction relies upon engrossing warmth in the event that it is to continue. 

The inverse of an endothermic process is an exothermic process, one that discharges, "gives out" energy or power as warmth. In this manner in each term (endothermic and exothermic) the prefix alludes to where heat goes as the reaction happens, however actually it just alludes to where the energy or power goes, without fundamentally staying as warmth.


Every chemical reaction includes both the breaking of existing bonds and the creation of new synthetic bonds. A reaction to break a bond dependably requires the contribution of energy or power thus such a process is constantly endothermic. At the point when iotas meet up or converge to shape new synthetic bonds, the electrostatic powers uniting them leave the bond with a substantial abundance of energy or power (normally as vibrations and pivots). On the off chance that that energy or power isn't disseminated, the new bond would rapidly break, thereby being separated once more. Rather, the new bond can shed its overabundance of energy or power - by radiation, by exchange to different movements in the atom, or to different particles through crashes - and after that turn into a stable new bond. Shedding this abundance of energy or power is the exothermicity that leaves the atomic framework. The tabulation and categorisation of whether a given primary or general reaction is exothermic or endothermic, is dictated by the overall commitment of these bond breaking endothermic advances and new bond balancing out exothermic advances. The idea is often connected in physical sciences for, for instance, synthetic reactions, where warm energy or power (heat) is changed over to concoction bond energy or power.

Endothermic (and exothermic) examination represents the enthalpy change (∆H) of a reaction. The full energy or power examination of a reaction is the Gibbs free energy or power (∆G), which incorporates an entropy (∆S) and temperature term notwithstanding the enthalpy. A reaction will be an unconstrained process at a specific temperature if the items have a lower Gibbs free energy or power (an exergonic reaction) regardless of whether the enthalpy of the items is higher. Entropy and enthalpy are distinctive terms, so the change in entropic energy or power can conquer a contrary change in enthalpic energy or power and make an endothermic reaction ideal.


A few instances of endothermic reactions are:

  • Photosynthesis

  • Dissolving of ice

  • Dissipating fluid water

  • Sublimation of carbon dioxide (dry ice), etc. 

What is Exothermic Reaction?

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An exothermic reaction is a concoction reaction that discharges energy through light or warmth. It is the inverse of an endothermic reaction. Communicated in a synthetic condition: reactants → items + energy. Exothermic Reaction signifies "exo" (got from the Greek word which roughly translated means "out") which means discharges and "thermic" signifies heat. So, the reaction in which there is arrival of warmth with or without light is called an exothermic reaction. An exothermic reaction is a compound reaction that discharges heat. It gives net energy to its environment. That is, the energy expected to start the reaction is not exactly the energy released. 

At the point when the medium in which the reaction is occurring gathers heat, the reaction is exothermic. When utilizing a calorimeter, the aggregate sum of warmth that streams into (or through) the calorimeter is the negative of the net change in energy of the framework. The total measure of energy in a compound framework is hard to gauge or ascertain. The enthalpy change, ΔH, of a substance reaction is a lot simpler to work with. The enthalpy changes levels with the change in inside energy of the framework in addition to the work expected to change the volume of the framework against consistent encompassing weight. A bomb calorimeter is entirely reasonable for estimating the energy change, ΔH, of an ignition reaction. Estimated and determined ΔH values are identified with bond energies by:

ΔH = (energy utilized in shaping item bonds) − (energy discharged in breaking reactant bonds) 

A few instances of exothermic reaction are:

  • Burning reactions of energizes or a substance

  • Balance

  • The thermite reaction

  • Reactions occurring in a self-warming can dependent on lime aluminium

  • Numerous consumption reactions, for example, oxidation of metals

Heat creation or assimilation in either a physical procedure or compound reaction is estimated utilizing calorimetry. One basic research centre instrument is the reaction calorimeter, where the warmth stream into or from the reaction vessel is checked.


The system can be utilized to pursue substance reactions just as physical procedures, for example, crystallization and disintegration. Energy discharged is estimated in Joule per mole. The reaction has a negative ΔH (heat change) esteem because of warmth misfortune.


How will it be ascertained that the Reaction is Endothermic or Exothermic?

An endothermic reaction douses up warmth. An exothermic reaction discharges heat. Endothermicity and exothermicity rely upon whether items or reactants have more energy (for reactions at steady volume) or a greater quantity of something many refer to as enthalpy (for reactions at fixed weight). The energies and enthalpies of numerous normal substances can be gazed upward in tables, albeit regularly you need to make a few redresses if the reactions are occurring at various temperatures or weights than the ones utilized for the tables. 

So, if the whole of the enthalpies of the reactants is more prominent than the items, the reaction will be exothermic. In the event that the item's side has a bigger enthalpy, the reaction is endothermic. 

It may be wondered as to why endothermic reactions, which douse up energy or enthalpy from nature, even occur. Most unconstrained occasions (like water streaming downhill) discharge energy to nature, warming it up. In any case, the guideline overseeing which way reactions (and different occasions) go is that the aggregate sum of something many refer to as entropy goes up. Entropy is a proportion of what number of various infinitesimal states things may be in. One approach to expand the entropy of the earth is to discharge heat into it, as in exothermic reactions. Be that as it may, now and again substances can expand their very own entropy a great deal by drenching up warmth, and afterwards endothermic reactions can happen, despite the fact that the earth loses entropy. 

A quantity called the Gibbs' Free Energy is utilized to monitor both the entropy change of the substances and the warmth discharged to the earth (and along these lines the earth's entropy change). For reactions at a steady weight, the Gibbs free energy goes down. Gibbs' free energies are likewise arranged for some substances under standard conditions.

Difference between Endothermic and Exothermic Reactions:

Endothermic Reactions Cool their Surroundings while Exothermic Reactions Make Surroundings Hotter 

From a science point of view, in chemistry, there is no such thing as cold - just a nonappearance of warmth. Endothermic responses draw heat energy into themselves. As that heat leaves the encompassing zone, the temperature drops. For instance, a first aid emergency treatment cold pack works as a result of an endothermic response among water and ammonium nitrate. Since it manoeuvres heat energy into the pack, the pack feels cold to the touch as it draws heat from the encompassing territory.

An exothermic reaction, on the other hand, sheds heat energy as the reaction advances, which means it emanates heat while it is going on. In a campfire, the energy from the synthetic obligations of the wood and paper is discharged as warmth and light. That discharged energy makes the encompassing zone hotter for cold campers.

Endothermic Reactions Contain More Energy while Exothermic Reactions Contain Much Lesser Energy

Endothermic responses attract and store energy as compound bonds created by the response. In an endothermic response, the item contains more net energy than the reactants did toward the beginning of the procedure. The results of the endothermic responses more often than not have more volume in view of the put away energy.

In any exothermic response, energy is expelled from the compound bonds in the reactants. This normally requires an underlying piece of energy called initiation energy to kick the procedure off, for example, a lit match or other use of warmth to begin that pit fire. After the exothermic procedure has completed, the item has lower heat and is commonly increasingly minimal.

Endothermic Reaction

Exothermic Reaction

A reaction which is basically made in the system where it absorbs energy from its surroundings in the form of heat.

A reaction which leaves energy from their system in heat form.

The “energy” is absorbed from the surrounding into the reaction.

The “energy” is released from the system to the environment.

“Energy”, is in heat form.

Its energy gets released to the environment in the form of heat, electricity etc.

Melting ice, evaporation, cooking, gas molecules, photosynthesis comes under this.

Rusting iron, settling, chemical bonds, explosions, nuclear fission

How to Prepare Notes on Endothermic and Exothermic Reactions?

  • Go through Difference Between Exothermic and Endothermic Reactions.

  • This page on Vedantu has all the relevant information that’s needed by the students.

  • They can write down each of the topics and sub-topics in their own language.

  • ‘They must not just copy-paste from here.

  • They can use drawing for the sake of clarity.

  • All the key areas can be highlighted using some coloured pen.

  • They must revise from here before an exam on the topic.

Does Vedantu Offer any Material on Exothermic and Endothermic Reactions?

Yes, Vedantu has ample material on both. Students can read from Difference Between Exothermic and Endothermic Reactions. This page has explained everything in a simplified manner to them so that they understand what each is.  A detailed description of the same has been mentioned here so that the students understand everything in a proper manner and then prepare for tests.

FAQs on Exothermic and Endothermic Reactions

1. What is photosynthesis an example of?

Photosynthesis is an example of an endothermic reaction. All endothermic reactions use heat as the source of energy. The descriptions for which have been provided on Difference Between Exothermic and Endothermic Reactions that are available on Vedantu. Each of the topics has been dealt with here and going through this page will enlighten all students about the topic. All major reactions that take place have been explained well here so that the students absorb and then implement the same in their exams. All topics covered here are of utmost importance.

2. Which reactions contain more energy?

Endothermic reactions contain more energy whereas exothermic ones contain much lesser energy. If the students read from Difference Between Exothermic and Endothermic Reactions, they will better understand all concepts. The reason behind why these reactions contain less or more energy has been explained. This page can be used by all students who wish to find out more about the topic as it has relevant information that will come for the tests. It is created by expert Science teachers who know the topic inside out.

3. Is rusting of iron an exothermic reaction?

Yes, rusting of iron is an exothermic reaction. More examples of exothermic reactions have been included in Vedantu’s portal that has Difference Between Exothermic and Endothermic Reactions. This page can be read by all those who need access to it as it contains all the information that students need. It is quite useful in terms of its content and knowing the different kinds of reactions and their energies will assist the students in doing well in all exams that come on the topic.

4. How can students make notes on Endothermic Reactions?

Students can read up Difference Between Exothermic and Endothermic Reactions on Vedantu’s e-learning platform and find out. They need to go through this topic well so as to understand the concepts well. A lot of explanation has been provided here which makes it easier for the students to know about the different topics. They can read this page and resolve all their doubts. They must also go through each and every example to be sure as the examples shed a lot of light on the sub-topics. Making notes before an exam is an effective way of studying as it involves paying close attention to all the details. Notes always come in handy as they have concise matter in them that can be utilized by all students to study well. All the vital portions can be marked using a highlighter pen as they will retain the material for a longer period of time in the student's mind.  Bullet points can also be used while writing down the pointers.

5. What is Gibbs Free Energy?

Gibbs Free Energy has been covered in Difference Between Exothermic and Endothermic Reactions that are on Vedantu’s online tutoring platform.  Students need to go through the entire page and then get to the part on Gibbs Free Energy. Before they read what’s on the page, they must read the topics well in advance. The concept has been explained well on this page and its relation to Endothermic and Exothermic energy have also been covered here. Students must highlight all the key areas so that it becomes easier for them to revise from here before an exam.