Why do substances burn with or without a flame?Have you ever observed either a coal or a wood fire? If not, the next time you get achance, take close note of what happens when the wood or coal starts to burn. Youhave seen above that a candle or the LPG in the gas stove burns with a flame. However,you will observe the coal or charcoal in an ‘angithi’ sometimes just glows red andgives out heat without a flame. This is because a flame is only produced when gaseoussubstances burn. When wood or charcoal is ignited, the volatile substances presentvapourise and burn with a flame in the beginning.A luminous flame is seen when the atoms of the gaseous substance are heated andstart to glow. The colour produced by each element is a characteristic property ofthat element. Try and heat a copper wire in the flame of a gas stove and observe itscolour. You have seen that incomplete combustion gives soot which is carbon. Onthis basis, what will you attribute the yellow colour of a candle flame to?

Subject: ScienceScenario : Ajay was watching television and saw the news about recurring fire accidents in coal mines.  He searched about the cause of these fire accidents. He found out that this happens due to the spontaneous combustion of coal dust in the mines, as coal dust unexpectedly bursts into flame without requiring any external ignition.He researched more about combustion and found out that it is a chemical process in which a substance reacts with oxygen to give off heat. The combustion process is of three types, as follows. Rapid Combustion Spontaneous combustion Explosive CombustionSubstance burns rapidly. Substance unexpectedly bursts into flame. Substance burns with sudden production of heat, light and sound.It releases a large amount of heat on burning. It releases a small amount of heat on burning. It releases a large amount of heat on burning.It requires an external ignition. No external ignition is required. It requires an external ignition.Example: the combustion of LPG Example: combustion of sodium on exposure to air Example: burning of firecrackers.Question:5 )  Ajay switches on the stove and brings a burning matchstick closer to the stove. Will the burning matchstick light up the stove?A)   Yes, the burning matchstick will light up the stove as the gas burns rapidly on external ignition.B)    No, the burning matchstick will not light up the stove, as the gas does not require any external ignition to burn.C)    No, the burning matchstick will not light up the stove as the gas is not getting any external heat from the matchstick.D)    Yes, the burning matchstick will not light up the stove as the gas burns spontaneously on coming out of the inlets of the stove.NEXT

10. When wood, natural gas, oil, or any other fuel burns, ..... with oxygen in the air to produce heat. Combining substances in the fuel Substances in the fuel that combine Substances in the fuel combine A combination of substances in the fuel

If a glass plate/slide is held into the luminous part of candle flame we see a circular blackish ring that represents:A.unburnt carbon particlesB.formation of coalC.burnt carbon particlesD.Both burnt carbon particles & formation of coal

Logs of pine wood are burning in a fireplace. What are two signs that a chemical change is happening to the wood?The wood is brownThe wood smells like pineThe wood turns blackHeat and light are releasedI'm not sure

Fossil fuels are nonrenewable resources because they took millions of years to attain their present form.We use fossil fuels such as coal, oil, and gas to heat our houses, run industry, and transport. They are usually hydrocarbons (compounds of carbon and hydrogen). When they are burnt, they combine with oxygen from the air. The carbon becomes carbon dioxide; hydrogen becomes hydrogen oxide called water; while energy is released as heat. In the case of coal:Carbon + Oxygen      →→  carbon dioxide + heat energyHydrocarbon + Oxygen    →→   carbon dioxide + water + heat energy