What is the difference between absorption and adsorption?

The distinction between absorption and adsorption is pivotal in understanding how substances interact with each other in various contexts, such as in biological systems or environmental science.

Absorption is the process by which a substance is taken up into the volume of another material. For example, when a liquid is absorbed by a sponge, the liquid fills the pores inside the sponge. In biological contexts, absorption often refers to how nutrients from food are taken into the body from the digestive tract.

In contrast, adsorption involves the adhesion of molecules from a gas, liquid, or dissolved solid to a surface. In this process, the molecules adhere to the surface of a material, creating a layer that is not part of the bulk material itself. An example can be seen with activated charcoal, which adsorbs impurities from a liquid or gas due to its large surface area.

This understanding of the two processes highlights the correct choice, which precisely defines absorption as the movement into organisms (concentrating on biological systems) and adsorption as the binding to surfaces. The other options misrepresent these fundamental characteristics, creating confusion about how substances interact in various environments.