Odour refers to which characteristic of a substance?

• A. Weight
• B. Odour is the characteristic smell of a substance.
• C. Volume
• D. Boiling point.

Answer: (B)

Odour is about the smell of a substance—the sensory property you notice when volatile molecules reach your nose. It comes from molecules evaporating from the substance and interacting with receptors in the olfactory system, giving each substance its characteristic scent. This is different from weight (how heavy it is), volume (how much space it occupies), or boiling point (the temperature at which a liquid boils). Odour can vary with concentration and conditions, and some substances are odourless, even though they have weight, volume, and other properties.