The correct option is A-1, B-4, C-3, D-2
Explanation
Combustion is a chemical process in which a substance reacts with oxygen to release heat. The visible characteristics of combustion-such as the presence of a flame, a glow, or an explosion-depend on the physical state of the substance and the rate of the reaction.- A. Magnesium (Matches 1): Magnesium is a reactive metal that burns with a dazzling white flame. A flame is produced only when a substance vaporizes during burning. Magnesium vaporizes during combustion, resulting in a distinct flame.
- B. Charcoal (Matches 4): Charcoal is a solid carbon fuel that does not vaporize upon heating. Since it does not turn into vapor, it does not produce a flame. Instead, it glows red-hot as the combustion reaction takes place on the surface of the solid.
- C. White Phosphorus (Matches 3): White phosphorus is a highly reactive non-metal with a very low ignition temperature (approximately 35°C). It undergoes spontaneous combustion, meaning it catches fire on its own when exposed to atmospheric oxygen at room temperature, without the application of external heat.
- D. Explosion (Matches 2): An explosion is a specific type of combustion characterized by a sudden reaction that evolves a large amount of gas. This rapid expansion is accompanied by the simultaneous release of heat, light, and sound (e.g., the ignition of firecrackers).
Key Takeaway: A flame is produced only by substances that vaporize during burning; solids that do not vaporize merely glow. Spontaneous combustion requires no external ignition source, whereas explosions are defined by the rapid evolution of gas, sound, and energy.