Adsorption vs Absorption – Learn the difference

Adsorption vs Absorption

Absorption is a chemical or physical process by which an ion, atom, or molecule enters a gas, liquid, or solid.

Adsorption is the physical process by which a liquid, gas, or suspended matter gathers on the surface of a substance.

A teacher, while grading essays of her students, comes across a strange sentence,

‘To become the Major of the town, I must have a Mayor in political science’

She immediately identifies the error. Her student has clearly not proofread his essay. Thanks to the context set by the rest of the sentence, the teacher understands the intended meaning, and ignores the silliness of her student.

If you think all misspellings are this harmless, or always end with only a disappointed sigh, you better have a close look on another such pair that is a popular error in academic writing!

Absorption and Adsorption

Absorption is a chemical or physical process by which an ion, atom, or molecule enters a gas, liquid, or solid.

For instance, absorption of water by sponge or filter paper.

On the other hand, adsorption is the physical process by which a liquid, gas, or suspended matter gathers on the surface of a substance.

For instance, adsorption of impurities by alum to purify water.

In a nutshell, both, absorption and adsorption involve interaction between two substances. But, while absorption is a bulk phenomenon, i.e., occurs throughout a material, adsorption is limited only to the surface of a material.

We use the word ‘absorption’ quite often in general communication, but ‘adsorption’, being a scientific term, is hardly used outside the academic setting. These two words are near homophones, but not interchangeable.

The distinction between absorption and adsorption might appear like a single-letter trifle but it holds great significance in academic writing.

How?

Let’s try to fill this blank: Roots of plants _____ water.

While one word (read absorb) presents a scientifically proven fact, another (read adsorb) frames a sentence which is confusing, questionable, and absolutely absurd!

Academic writing demands concise and clear communication of information. It is based on evidence and observations that cannot be distorted. Hence, using the correct word is not just expected, but also necessary!

Here are more examples for the correct usage of absorption and adsorption.

Incorrect: Solar radiation is adsorbed in the Earth’s atmosphere.

Correct: Solar radiation is absorbed in the Earth’s atmosphere.

Incorrect: Gases are absorbed on the plane surfaces of glass.

Correct: Gases are adsorbed on the plane surfaces of glass.

Tips to remember the difference

While ‘absorption’ and ‘adsorption’ have quite distinct meanings, how do you remember them? Here are some easy tips to help you out:

1. ‘B’ for Bulk: The ‘b’ in absorption can help you remember that it is a ‘bulk’ phenomenon, meaning it happens well beyond the surface!
2. Practice makes perfect: Quite an archaic suggestion, but it always works! Try writing down multiple examples of ‘absorption’ and ‘adsorption’ to grasp their meanings.

Now that we have unraveled absorption and adsorption, tell us which other confusing words would you like us to decode next!