Difference Between Endothermic and Exothermic Reactions in Tabular Form

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Wanna know what is the difference between endothermic and exothermic reactions in tabular form? If yes, then look no further! As per the laws of thermochemistry, a chemical reaction can be divided into two sub-categories. These are endothermic and exothermic reactions.

The primary difference between endothermic and exothermic reactions is that an endothermic reaction absorbs energy from its surroundings. And, an exothermic reaction releases energy to its surrounding.

The energy released or absorbed can be either in the form of heat, cold, light, or, sound. No wonder, there are so many differences between them. But before going ahead, let me give you a brief review of the two in a tabular form. Let’s dive right in…!!!

 

Endothermic vs Exothermic

 Endothermic ReactionExothermic Reaction
1.An endothermic reaction absorbs energy from its surroundings.An exothermic reaction releases energy to its surrounding.
2.Energy is absorbed in the form of heat.Energy is released in the form of sound, heat, and light.
3.The change in enthalpy is positive.The change in enthalpy is negative.
4.Enthalpy of products is always greater than the reactants.Enthalpy of products is always less than the reactants.
5.Temperature decreases with the progression of endothermic reactions.Temperature increases with the progression of exothermic reactions.
6.An endothermic reaction is a type of endergonic reaction.An exothermic reaction is a type of exergonic reaction.
7.Examples of endothermic reactions include Evaporation, Instant Cold packs, cooking, etc.Examples of exothermic reactions include condensation, nuclear reactions, rusting of iron, etc.
From the above difference between endothermic and exothermic reactions in tabular form, you got the exact overview of these two. However, to get to know them, let us try to understand both of them in a detailed format. Keep reading!

 

What are Endothermic Reactions?

drying-wet-clothes-endothermic-example
Image Source: Farmer’s Almanac

By definition, Endothermic reactions are a type of chemical reaction during which a system absorbs energy from its surroundings. One can also say that the endothermic process requires additional energy from its surroundings to proceed further. That is why the temperature of the surroundings decreases.

For example, in the case of drying wet clothes, the water droplets inside the clothes (system) pull the heat from the surroundings. As a result, the enthalpy of the system (wet clothes) increases which in turn decreases the temperature of the surrounding, at least, a little bit.

Why Change in Enthalpy of Endothermic Reactions is always positive?

endothermic-reaction-diagram
Image Source: Socratic

Just because the energy (heat) is absorbed by the system from its surroundings, the change in enthalpy of endothermic reactions is always positive. Not to mention, as per other definitions, the enthalpy (energy) of products is higher than the reactants. That’s why always a positive value. (See the above diagram and equation written below to understand it properly)

A + B => C +D

ΔH = {HC + HD} – {HA + HB}

ΔH = (Hproducts – Hreactants ) = positive value

where,

A and B are Reactants

C and D are Products

ΔH = Change in enthalpy during the reaction

HA and HB = Enthalpy of A and B

HC and HD = Enthalpy of C and D

Examples of Endothermic Reaction

Some of the examples of Endothermic reactions are:

  • Evaporation
  • Photosynthesis
  • Instant Cold Pack
  • Cooking food
  • Salt Dissolving in Water
  • Sublimation
  • Thermal Decomposition
  • Pressure Cookers
  • Hydrolysis, etc.

 

What are Exothermic Reactions?

nuclear-explosion-exothermic-reaction
The mushroom cloud over Hiroshima and Nagasaki. Image Credit: Wikimedia Commons

By definition, Exothermic reactions are a type of chemical reaction during which a system releases energy to its surroundings. One can say that the exothermic process releases additional energy to its surroundings to proceed further. That is why the temperature of the surroundings increases.

For example, in the case of nuclear fission reaction, when the uranium is bombarded with a neutron. It splits into two smaller nuclei releasing a large amount of energy which in turn increases the temperature of the surroundings.

Why Change in Enthalpy of Exothermic Reactions is always negative?

exothermic-reaction-diagram
Image Source: Quora

Just because the energy (heat) is released by the system to its surroundings, the change in enthalpy of exothermic reactions is always negative. Not to mention, as per the other definition, the enthalpy (energy) of the products is less than the reactants. That’s why always a positive value. (See the above diagram and equation written below to understand it properly).

S + T => U +V

ΔH = {HU + HV} – {HS + HT}

ΔH = (Hproducts – Hreactants ) = negative value

where,

S and T are Reactants

U and V are Products

ΔH = Change in enthalpy during the reaction

HS and HT = Enthalpy of S and T

HU and HV = Enthalpy of U and V

Examples of Exothermic Reaction

Some of the examples of Exothermic reactions are:

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I am a mechanical engineer by profession. Just because of my love for fundamental physics, I switched my career, and therefore I did my postgraduate degree in physics. Right now I am a loner (as ever) and a Physics blogger too. My sole future goal is to do a Ph.D. in theoretical physics, especially in the field of cosmology. Because in my view, every aspect of physics comes within the range of cosmology. And I love traveling, especially the Sole one.

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