Fog is a colloidal solution of
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Liquid in gas
Fog forms when moist air is cooled below its dew point: water condenses into fine droplets that stay suspended in air. The dispersed phase is a liquid (water droplets) and the dispersion medium is a gas (air). Such a colloid is an aerosol; mist, clouds and insecticide sprays are other examples.
Why the other options are incorrect
Option (1) Solid in gas — Incorrect. This is also an aerosol, but with solid particles, e.g. smoke and dust.
Option (2) Gas in gas — Incorrect. Gases mix completely to form a true solution, so a gas-in-gas colloid is not possible.
Option (4) Gas in liquid — Incorrect. This is a foam, e.g. froth, whipped cream, soap lather.
Note 1: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Classification Based on Physical State of Dispersed Phase and Dispersion Medium – …
Note 2: The same/similar question has been asked in different years by NTA as per the details given below:
| 2026 | 2025 | 2024 | 2023 | 2022 |
|---|---|---|---|---|
| – | – | – | 02-06 S3 31-05 S1 | – |