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Smoke is a common phenomenon observed during the combustion of materials such as wood, coal, or incense. It consists of solid particles (like carbon, ash, and other residue) suspended in the gas phase (air). In chemistry, smoke is classified as a heterogeneous mixture, but in terms of dispersal, it can also be described as a colloidal system where solid particles are distributed throughout a gas.
When a substance burns incompletely, some of its carbon and other components do not convert fully into gas.
These solid particles are carried by the hot gases produced during combustion.
The combination of hot gases and suspended solid particles is what we observe as smoke.
Composition: Tiny solid particles (carbon, ash, soot) in air.
Appearance: Usually gray or black depending on the material burned.
Behavior: Solid particles in smoke are light enough to remain suspended for some time before settling.
Colloidal Nature: Smoke is considered a colloidal dispersion because the particle size is intermediate between true solutions and suspensions.
| Mixture Type | Example | Notes |
|---|---|---|
| Solid in solid | Alloys (e.g., brass) | Not smoke |
| Solid in liquid | Sugar in water | Not smoke |
| Solid in gas | Smoke, dust in air | Correct |
| Gas in gas | Air, oxygen in nitrogen | Not smoke |
Smoke analysis helps study pollution and air quality.
Understanding smoke is important in fire safety, industrial processes, and health science, as inhaled smoke can cause respiratory issues.
Smoke = solid particles in gas
Forms from incomplete combustion
Can be classified as a colloidal dispersion
Key examples: soot from wood, coal, incense
👉 Correct Answer: Option 3 – Solid in gas
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