What type of mixture is smoke ?

Smoke is a complex heterogeneous mixture, specifically a solid-in-gas aerosol. It is formed during the incomplete combustion of materials, resulting in tiny solid particles such as carbon (soot), ash, and tar being suspended in the air [2]. These solid particles are often nanoscale carbonaceous materials that act as nuclei for vapors. In chemical terms, smoke is classified as a colloid or a suspension depending on the particle size; if the particles are between 1 nm and 1000 nm and do not settle, it is a colloid [1]. These solid particles are constantly hit by invisible gas molecules, which keeps them suspended in the gaseous medium [1]. While some smoke may contain liquid droplets (like water or oils), the fundamental definition of smoke in general chemistry refers to solid particles dispersed in a gas.

Sources

1. [2] https://www.sciencedirect.com/science/article/pii/S0165237024001335
2. [1] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 7: Particulate Nature of Matter > Safety first > p. 106