exothermic reaction



We explain what an exothermic reaction is and its differences with an endothermic reaction. Also, examples of this chemical reaction.

Exothermic reactions release energy.

What is an exothermic reaction?

An exothermic reaction is one that when it occurs releases energy in the form of heat or light to the environment. When this type of reaction occurs, the products obtained have lower energy than the initial reactants.

Enthalpy is a quantity that defines the flow of thermal energy in the chemical processes that occur at Pressure constant. Furthermore, this magnitude represents the exchange of Energy between a thermodynamic system and its environment. The variation of this magnitude (ΔH) in a chemical reaction is used to classify it as endothermic or exothermic.

ΔH> 0 endothermic reaction.

ΔH <0 exothermic reaction.

Exothermic reactions are very important in biochemical sciences. Through reactions of this kind, organisms living beings obtain the necessary energy to sustain the life in a process called metabolism.

Most of the exothermic reactions are of oxidation, and when they are very violent they can generate fire, as in the combustion. Other examples of these reactions are transitions of the matter of a State of aggregation to another of lower energy, such as gas to liquid (condensation), or from liquid to solid (solidification).

In fact, many exothermic reactions are dangerous for the Health because the energy released is abrupt and uncontrolled, which can cause burns or other damage to the living creatures.

Differences between exothermic and endothermic reactions

Endothermic reactions absorb energy, like chemical ice.

In all chemical reaction energy is conserved. This constitutes the energy conservation law: energy is neither created nor destroyed, it is only transformed.

In endothermic reactions, energy is absorbed to transform reactants into products. In this type of reaction, the bonds of the molecules that make up the reactants are broken down to form new components. This bond-breaking process requires the energy in question. An example of this is the electrolysis process of Water, where it is supplied electric power to the water molecule to break it and transform it into its constituent elements.

On the other hand, in exothermic reactions, reactants release chemical energy contained in the bonds that make up its molecules. The energy released can be in the form of heat or light.

Examples of exothermic reaction

Glucose oxidation is an exothermic reaction.

Some known exothermic reactions are:

  • The combustion. It is a reaction of oxidation very fast that occurs between materials called fuels and oxygen. Fuels are made up mainly of carbon, hydrogen and, in some cases, sulfur. Examples of fuels are methane gas, gasoline, and natural gas. This reaction releases large amounts of heat, which can lead to fire.
  • The oxidation of glucose. This is the reaction we carry out animals to obtain metabolic energy: we take oxygen from the breathing and we use it to oxidize sugars, breaking the glucose molecule into simpler molecules (glycolysis) and obtaining as a reward molecules of ATP, rich in chemical energy.
  • The mixture of potassium and Water. Potassium is a powerful desiccant that, when mixed with water, releases hydrogen and enormous amounts of energy in an explosion. This occurs with all alkali metals, although not always with the same amount of energy released.
  • The formation of ammonia. To form ammonia (NH3), nitrogen (N2) and hydrogen (H2) are reacted, which means obtaining a less energetic molecule than the molecules put into reaction. That difference in energy must be released, and it occurs as an increase in temperature (heat).
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