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Combustion - Key Points | Combustion meaning - & chemical process where a substance reacts with oxygen and 4 P a) A produces heat. 2. Sometimes, it alco gives off light โ this light may appear as a flame or as a glow ostance that burns is calleq combustible substance. hk combustible substance is alco called fuel. 5. Fuels can be sold, liquid, or gas, b. Example : Magnesium ribbon burns to form magnesium oxide and gives out heat and light. 1. Example 2: Charcoal burns in air to produce carbon dioxide, heat, avd light. & Example % Coal alco burns in air to give carbon dioxide, heat, and light. 4. In burning of magnesium and charcoal โ bot magnesium and charcoal are combustible substances. lo. Heat released in combustion can be used for various purposes like cooking or heating, IL Light produced in combustion can be seen as a flame (eg, cavdle) or a5 a gow (eg, burning charcoal). se 12. Fuel is something that stores enerqy and can burn to gne heat and sometimes light. Xe %. Combustion needs onygen to take place. Created with 4. Without odygen, combustion will not happen. Notewise 15. Our body alco needs fuel โ food acts as fuel for our body, io. Energy from food is used for body functions like movement, growth, and vepaiv. iT. Burning of substances is a chemical change โ new substances are formed. 8. Magnesium burning forms magnesium oxide as the new substance. nN A. Charcoal and coal burning form carbon dioxide as the new substance. 20. Ml fuels are vot the same โ they may produce different amounts of heat and light. Ketnity | outer zone of hottest complete โ ยป part combustion (blue) moderately hot middle zone of partial combustion least (yellow) Lones ofa Candle Flamd ey innermost zone 0: 1. Ouker Zone wax candle unburnt wax vapours (black) Colour: Blue. Type of combustion: Complete combustion. Hottest part of the Plame. Ke Ww AU was: vopours gef enough oxygen here, 40 they Burn completely. 2) tictawise fire extinguisher The most common fire = extinguisher is water. But โโ water works only when 7 things like wood and paper are on fire. If electrical i BAA } Ea equipment is on fire, water may conduct electricity and harm those trying to douse the fire. Water is also not suitable for fires involving oil and petrol. Do you recall that water is heavier than oil? So, it Fig. 6.7 : Fire extinguisher sinks below the oil. and oil keeps burning on the top. For fires involving electrical equipment and inflammable materials like petrol, carbon dioxide (CO,) is the best extinguisher. CO,. being heavier than oxygen. covers the fire like a blanket. Since the contact between the fuel and oxygen is cut off, the fire is controlled. The added advantage of CO, is that in most cases it does not harm the electrical equipment. How do we get the supply of carbon dioxide? It cam be stored at high pressure as a liquid in cylinders. In what form is the LPG stored in cylinders? When released from the cylinder, CO, expands enormously in volume and cools down. So, it not only forms a blanket around the fire, it also brings down the temperature of the fuel. That is why it is an excellent fire extinguisher. Another way to get CO, is to release a lot of dry powder of chemicals like sodium bicarbonate (baking soda) or potassium bicarbonate. Near the fire, these chemicals give off CO,. Created with Notewise VectorStock Created with Notewise did you know! Ke monoxide (CO) โ poisonous gas, can cause death in closed spaces. LPG. (Liquefied Proleun Gas): Stored as liquid under pressure, Burns as gas. CNG, (Compressed Nafurall Gas) and LPG are called clean fuels Because they produce loss smoke and leave loss residue Soot is unburnt carbon particles formed in incomplete combustion โ black deposits Ce.g., on ukensils heabed over a smoky flame). oF Fuel Impacts Include: x w 59 โG3 Ae BAY Ocean Extreme SeaLevel โ Plastic Air Water oil Health Acidification Weather Rise Pollution Pollution Pollution Spills โ_ Issues Graphic by Emma Johnson, EES! Calorific Values of Common Fuels aie Created with COmourd of heat produced by Gunning 1 hg of fuel โ unit: h/leg) @ Notewise Fuel Calorific Value (&d/tg) Cow dung cakeeoo0-8000 Wood17000-22000 Coal 25000-33000 Pekrol 45000 Kerosene 45000 Dieselasoo0 Mefhanes0000 CNGs0000 LPG 55000 Biogas 35000-40000 FHydrogen 150000 Ww Ww Health Hazards of Bunning Fuels Incomplete combustion produces carbon monoxide (CO) as colourless, odourbess, poisonous gas that can cause headaches, unconsciousness, or death. Smoke contains fine particles = causes respiratory problems like asthma and bronchitis. Sulphur dioxide (SO,) and nitrogen oxides (LO) from burning coal and diesel cause acid vain โ damages crops, soil, and buildings. Long-term exposure to polluted ain. heart and lung diseases. vy Created with Notewise 
