Combustion and Flame
Combustion is the act of burning. Combustion is a chemical process in which a substance reacts with oxygen to produce heat and light. Combustion is of three types- rapid combustion, spontaneous combustion and explosion. On the basis of combustion, substances are classified as combustible and non-combustible substances. Air, fuel and ignition temperature are essential for combustion. Ignition temperature is the minimum temperature at which a substance catches fire and starts burning.
Fire is the process of the oxidation of a combustible material by which heat and light are released and product such as carbon dioxide is formed. Water and carbon dioxide acts as fire extinguishers as they stops the supply of air or brings down the temperature of fuel. When a substance vapourises during burning, a shiny light producing heat is obtained. The shiny light is called flame. A flame has three zones- outer or non-luminous zone, middle or luminous zone and innermost or dark zone.
Fuel is a combustible substance and is the raw material for fire. A fuel may be solid, liquid or gaseous. There are different types of fuels such as petroleum, wood, coal etc. Fuel efficiency is expressed in terms of its calorific value. An ideal fuel has calorific value, high efficiency and is readily available.
Combustion produces some harmful substances which pollute the environment and cause diseases in living organisms. When rain water dissolves, the oxides of sulphur and nitrogen, acid rain is formed. The increased concentration of carbon dioxide in air causes global warming.