Absorption: Definition, Types, Process and Examples

Absorption: What happens when you soak a sponge in a dye? Does the colour change only on the surface of the sponge, or does the entire sponge get coloured? What is this phenomenon called? Is there any application of this in our daily life? Let us gain insight on Absorption, how it is different from adsorption, and many more.

Absorption: Definition

Sponge, when dipped in the coloured solution, completely changes in colour. This colour change is due to the two phenomena, i.e., adsorption and absorption. When these two phenomena occur simultaneously, it is called sorption.

Absorption occurs inside the surface and is a slower process. It is endothermic by nature.

Where Can We Find Absorption?

Example 1: Plants absorb carbon dioxide, water, and nutrients for photosynthesis.

Example 2: Ammonia gas in contact with water gets absorbed into the water, giving ammonium hydroxide solution of uniform concentration.

Example 3: If silica gel is kept in a vessel containing water vapours, the water vapours are adsorbed on the silica gel. On the other hand, if the anhydrous calcium chloride is kept in the place of the silica gel, Absorption occurs as the water vapours are uniformly distributed in calcium chloride to form hydrated calcium chloride.

Difference Between Absorption and Adsorption

The uniform distribution of the molecular species throughout the bulk is called Absorption. The phenomenon of attracting and retaining the molecules of a substance on the surface of a liquid or a solid resulting in a higher concentration of the molecules on the surface is called adsorption.

For example, when a chalk stick is dipped in ink, the surface attains the colour of the ink due to the adsorption of coloured molecules, while the solvent of the ink goes deeper into the stick due to Absorption. On breaking the chalk stick it is found that it is white from inside.

Water vapours are absorbed by the anhydrous calcium chloride, while these are adsorbed by silica gel. In other words, in adsorption, the concentration of the adsorbate increases only at the surface of the adsorbent, while in Absorption, the concentration is uniform throughout the bulk of the solid.

According to McBrain, when adsorption and Absorption occur simultaneously, it is called sorption. However, adsorption is instantaneous, which is fast, while Absorption is a slow process. For example, Dyes get adsorbed as well as absorbed in the cotton fibres; that is, sorption takes place.

Absorption	Adsorption
1. It is a bulk phenomenon.	1. It is the surface phenomenon.
2. The substance getting absorbed is distributed uniformly throughout the bulk of the substance.	2. The substance is accumulated at the surface of the solid. Thus, the concentration of the adsorbed substance is higher at the surface than in bulk.
3. It occurs at a uniform rate.	3. It is rapid at the beginning and slows down near the equilibrium.
4. It does not affect the temperature.	4. It occurs at a low temperature.
5. Concentration is the same throughout the material.	5. Concentration of material on the surface of the adsorbent is different from that in bulk.
6. It is an endothermic process	6. It is an exothermic process.
7. Example: a) Water vapours absorbed by anhydrous calcium chloride b) Ammonia is absorbed in water forming, ammonium hydroxide.	7. Example: a)Decolourisation of sugar by activated or animal charcoal. b)Oxygen is adsorbed on a tungsten surface.

Absorption in Human Body

Absorption is one of the significant processes of digestion. Absorption is the process by which end products of digestion pass through the mucosa cells into blood or lymph to be transported to various body cells. Substances absorbed are monosaccharides, amino acids, glycerol, fatty acids, vitamins, salts, etc. Significant Absorption occurs in the small intestine, followed by the large intestine.

Summary

The uniform distribution of the molecular species throughout the bulk is called absorption. It is different from adsorption in the way that The phenomenon of attracting and retaining the molecules of a substance on the surface of a liquid or a solid resulting in a higher concentration of the molecules on the surface is called adsorption. This article is a small interconnecting link for absorption by understanding the meaning, type, and uses of absorption. In addition, the article is useful in identifying absorption in our daily life. We also learnt about the process of absorption in the human body.

FAQs About Absorption

Below are the frequently asked questions on Absorption:

Q.1. What is the definition of absorption in biology?
Ans: Absorption is the process by which end products of digestion pass through the mucosa cells into blood or lymph to be transported to various body cells.

Q.2. What is the absorption of the wave?
Ans: Absorption of the wave is the transfer of the energy of a wave to matter as the wave passes through it.

Q.3. What is absorption in simple words?
Ans: The uniform distribution of the molecular species throughout the bulk is called Absorption.

Q.4. What is the difference between adsorption and absorption?

Absorption	Adsorption
1. It is a bulk phenomenon.	1. It is the surface phenomenon.
2. The substance getting absorbed is distributed uniformly throughout the bulk of the substance.	2. The substance is accumulated at the surface of the solid. Thus, the concentration of the adsorbed substance is higher at the surface than in bulk.
3. It occurs at a uniform rate.	3. It is rapid at the beginning and slows down near the equilibrium.