Which statement correctly distinguishes adsorption from absorption?

• A. Absorption is surface accumulation of particles; adsorption is bulk uptake into the volume.
• B. Adsorption is surface accumulation of particles; absorption is bulk uptake into the volume.
• C. Adsorption is a chemical reaction; absorption is a physical process.
• D. Adsorption occurs only on solids; absorption only in liquids.

Answer: (B)

The main idea is where the material goes: on the surface versus into the interior. Adsorption is when molecules accumulate or stick to a surface, forming a coating or film on the exterior without becoming part of the interior. Absorption is when those molecules are taken into the volume of the material, spreading throughout its interior and often causing the material to swell or become infused with the substance. An example helps solidify this: a dye that sticks to a charcoal surface demonstrates adsorption, while water soaking into a sponge shows absorption.

Why this is the best description: it captures the essential difference in location—surface versus bulk. The other statements mix up or oversimplify aspects that aren’t defining: adsorption is not inherently a chemical reaction (it can be physical or chemical), and absorption is not restricted to liquids or solids in any one direction.