Combustion and Flame - III

The head of a safety match contains an oxidizing agent, typically potassium chlorate (KClO3), which provides oxygen to sustain combustion when the match is struck. Phosphorus pentoxide (P2O5) is not used on match heads. Potassium chloride (KCl) is different from potassium chlorate.

A supporter of combustion is a substance that enables or supports burning. Oxygen is essential for combustion as it reacts with fuel during the burning process. Carbon dioxide (CO2) is actually used to extinguish fires by displacing oxygen. Water vapor and sand do not support combustion.

Ignition temperature is the minimum temperature to which a substance must be heated for it to catch fire and continue burning. It's a specific threshold for each combustible material. Option A correctly defines this. Option B incorrectly describes the maximum flame temperature, not ignition point. Option C describes fire point or burning temperature, not ignition.

In a safety match, the striking surface contains red phosphorus. When the match is struck, friction converts red phosphorus to white phosphorus, which ignites and initiates the combustion of potassium chlorate and antimony trisulfide on the match head. Red phosphorus on the side surface ignites FIRST, then transfers heat to the match head.

Kerosene oil has the lowest ignition temperature among the options - it vaporizes easily and catches fire at relatively low temperatures (approximately 210°C). Wood requires much higher temperatures (around 300°C), charcoal needs even higher heat, and cooking oil has a higher flash point (around 300-350°C) than kerosene. The ease of vaporization affects ignition temperature.

Carbon dioxide is the best fire extinguisher among these options because it's heavier than air, forms a blanket that displaces oxygen, and doesn't conduct electricity (safe for electrical fires). Water can spread grease fires and conducts electricity. Woollen cloth can smother small fires but is not as effective or versatile as CO2 for general firefighting.

When water is heated in a paper cup over a flame, the water absorbs the heat through conduction and convection. The water's boiling point (100°C) is well below the paper's ignition temperature (233°C or higher). As long as water remains in the cup, the paper cannot reach its ignition temperature, preventing it from burning.

Carbon dioxide (CO2) is heavier than oxygen and air, which allows it to settle and form a blanket over burning material, displacing the oxygen needed for combustion. CO2 does NOT react with oxygen (option A is wrong), and it does NOT raise temperature (option D is wrong). Its effectiveness comes from being denser than oxygen and physically displacing it.

Charcoal does NOT vaporize when burned - it undergoes solid-to-gas combustion where carbon directly reacts with oxygen, producing CO2 without passing through a liquid or vapor phase. Wax, kerosene, and wood all vaporize first (solid/liquid → gas) before burning - the combustion occurs in the gas phase. This is why charcoal leaves ash residue while the others burn away more completely.

Coal combustion produces carbon dioxide (CO₂) from the carbon content, and releases heat and light energy. Hydrogen gas (H₂) is not a direct product of coal burning; the hydrogen in coal combines with oxygen to form water vapor (H₂O), not hydrogen gas.

Combustion can occur in all three states of matter. Solid fuels like wood and coal burn, liquid fuels like petrol and alcohol burn, and gaseous fuels like natural gas and LPG burn. The physical state does not prevent combustion if the ignition temperature is reached.

Inflammable substances have very low ignition temperatures, meaning they can catch fire very easily with minimal heat input. Examples include petrol, alcohol, and LPG. The term 'inflammable' is synonymous with 'highly flammable'.

Wood has a relatively high ignition temperature (around 300°C). A matchstick produces brief, localized heat that is insufficient to raise the wood's temperature to its ignition point before the match extinguishes. Sustained contact or kindling is needed to reach the ignition temperature.

The fire triangle requires three essential components: fuel, oxygen (or an oxidizing agent), and heat. These three must be present for fire to exist. Carbon dioxide is NOT required for fire - in fact, it's used to extinguish fires by displacing oxygen.

Safety match heads contain antimony trisulfide (the fuel), potassium chlorate (the oxidizing agent), and powdered glass (abrasive). The striking surface contains red phosphorus. When the match is struck, friction generates heat, the red phosphorus converts to white phosphorus, which ignites the potassium chlorate, starting the combustion of antimony trisulfide.

Petrol, alcohol, and LPG have very low ignition temperatures and are classified as inflammable (easily ignitable). Wood is combustible but has a relatively high ignition temperature and requires sustained heat to burn. Wood is not considered an inflammable substance in the strict sense.

Correct Answer: Only I