AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.
When a saturated hydrocarbon burns in a limited supply of air, incomplete combustion occurs, producing a yellow, sooty flame, and a black sooty (carbon) deposit forms on the surface held above it.
The key phrase is "limited supply of air" — this causes incomplete combustion even of saturated hydrocarbons (which normally give a clean blue flame). Examiners expect both parts: type of flame (yellow/sooty) and the deposit (soot/carbon). Source: Chapter 4, Section 4.3.1 (Combustion).