Chapter 4: Conbustion and Flame

Answer: Knowing the ignition temperature of substances is crucial as it helps in assessing the potential for accidental fires and in designing safety systems. It ensures that substances are stored and used at safe temperatures, preventing them from catching fire spontaneously.

Answer: To control a fire using a fire extinguisher, identify the type of fire, select the appropriate extinguisher, pull the pin, aim the nozzle at the base of the fire, and squeeze the handle while sweeping side to side. Ensure an escape route is behind you and evacuate if the fire is not quickly controlled.

Answer: Using fossil fuels for combustion releases carbon dioxide, contributing to global warming. It also emits sulfur and nitrogen oxides, causing acid rain that damages ecosystems, and releases particulates that can cause respiratory issues. Switching to cleaner alternatives can mitigate these impacts.

Answer: LPG is an ideal domestic fuel because it burns more efficiently with higher calorific value, produces less smoke and pollutants, is easier to store and transport, and does not contribute to deforestation like wood.

Answer: The structure of a candle flame illustrates combustion principles with its distinct zones: an inner zone of unburnt wax vapors, a middle luminous zone where incomplete combustion occurs, and an outer non-luminous zone of complete combustion, showcasing how varying availability of oxygen affects the combustion process.

Answer: Oxygen is essential in the combustion process as it reacts with the fuel, allowing it to burn. The chemical reaction releases heat and light, and without sufficient oxygen, combustion becomes incomplete, producing smoke and soot.

Answer: Rapid combustion happens when a substance quickly ignites and burns to release energy, requiring an external ignition source, unlike spontaneous combustion, which occurs without any apparent external ignition due to instability or self-heating of the substance.

Answer: Dry wood is easier to ignite because it lacks moisture that requires additional energy to evaporate, allowing the temperature to rise more rapidly to its ignition point. Wet wood uses much of the energy from a flame to evaporate water, delaying combustion.

Answer: Carbon dioxide helps extinguish fires by displacing the oxygen around the fuel, cutting off the oxygen supply necessary for combustion. Additionally, it cools the fuel since it is released from high-pressure cylinders as a cold gas.

Answer: When storing flammable substances, they should be kept in well-ventilated, cool areas away from sparks or open flames, in fire-resistant containers, and clearly labeled. Storage areas should be secured to prevent unauthorized access and comply with safety regulations.