Endothermic Reactions

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Endothermic reactions can be defined as reactions that require external energy to proceed. The external energy is often present in the form of heat. They tend to cause their environments to cool down because endothermic reactions draw heat from their environments. As endothermic reactions yield higher energy products than the reactants, they are also usually non-spontaneous.  The change in enthalpy is always positive for an endothermic reaction.

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The products are higher in energy than the reactants in an endothermic response. The change in enthalpy is therefore positive, and the reaction absorbs heat from the surroundings. The heat is taken up from the atmosphere in such reactions, and hence the temperature of the system where the reaction goes stays cooler. In addition, at the end of the reaction, the enthalpy, which is the difference in heat energy during the transfer of reactants to the products, becomes greater.

In a chemical reaction, the breaking and making of chemical bonds transform reactants into products. The burning of carbon with oxygen to make carbon dioxide is an example. Bond breaking involves energy, while energy is released by bond forming. The equilibrium between the two produces a positive or negative change in energy for the reaction. Chemical reactions are categorized as either endothermic, with a change in positive energy, or exothermic, with a change in negative energy. More energy is taken from breaking bonds in an endothermic reaction than is released to produce them, so the reaction proceeds with net energy absorption. The opposite is true in an exothermic response, and energy is released.

Compounds produced by endothermic reactions have stored or potential chemical energy in their bonds, which may be released spontaneously in the event of an explosion. Chlorates, perchlorates, and nitrates contain certain compounds. This can spontaneously combust, making them dangerous to deal with whether there is any criminal intent or not. They can create a high explosive blend if combined with other materials.

Explosions of endothermic compounds usually create a lot of gas, producing a destructive wave of pressure that travels through the surrounding environment. The explosion of the endothermic substance is itself exothermic, with the chemical potential energy of the compound being released in heat, light, and sound. Endothermic explosions are also possible, but they need some primer explosive to give them the energy they need to set them off.

Endothermic Reaction Examples

  1. Photosynthesis-Chlorophyll in green plants helps to transform the water and carbon dioxide into glucose and oxygen in this process. And that is why it is an energy provider. 

  2. When a small quantity of ammonium chloride is taken with water into a test tube. Then we can see that it gets cooler in the test tube. Thus, heat is absorbed from the tube of the surrounding means test. 

  3. Conversion of ice by boiling, melting, or evaporation into water.

  4. Cooking an egg is an endothermic reaction. However, the energy from the pan is absorbed for cooking the egg in this endothermic reaction.

Difference Between Endothermic and Exothermic Reactions

  1. Chemical reactions involving the use of energy at the time of dissociation to create a new chemical bond are known as endothermic reactions, whereas exothermic reactions are those chemical reactions in which the energy is evolved or released. This is done in the form of heat

  2. There is a need for energy in the form of heat in the endothermic process, while energy in the exothermic process grows or is released.

  3. The value of ΔH is positive because the heat is absorbed in an endothermic reaction. On the other hand, in exothermic reactions, the value of ΔH is negative because heat is evolved.

  4. The conversion of ice into water vapor by boiling, melting, or evaporation, the splitting of gas molecules, the formation of anhydrous salt from hydrate are a few typical examples of an endothermic reaction. Examples of exothermic reactions are ice formation from water, coal-burning (combustion), and the reaction between water and strong acid.


  • More energy is taken from breaking bonds in an endothermic reaction than is released to create them, so the reaction proceeds with a net energy absorption.

  • Endothermic reaction compounds have stored or potential chemical energy in their bonds, which may spontaneously be released in an explosion.

FAQ (Frequently Asked Questions)

1. Explain the Differences Between Endothermic and Exothermic Reactions?

Answer: An endothermic reaction soaks up heat. Heat is produced by an exothermic reaction. Endothermicity and exothermicity depend on whether there is more energy (for constant volume reactions) or anything called enthalpy in products or reactants (at a fixed pressure). In tables, the energies and enthalpies of many common substances can be looked up, but if the reactions occur at different temperatures or pressures than those used for the tables, you also have to make some corrections.

2. During the Endothermic Reaction, What Form of Energy Transfer Would Occur?

Answer: kinetic energy to chemical energy. Heat is absorbed in the endothermic reaction and then converted into chemical energy. Remember that the measure of heat is the temperature, and it is not energy in itself.