This PSEB 8th Class Science Notes Chapter 6 Combustion and Flame will help you in revision during exams.
PSEB 8th Class Science Notes Chapter 6 Combustion and Flame
→ Fuels of different varieties are used for various purposes.
→ Fuels are used in homes, industries, automobiles.
→ Cowdung, wood, coal, charcoal, petrol, diesel, natural gas. L.P.G. etc. is various fuels.
→ Some fuels burn with flame and some do not give a flame on burning.
→ Combustion is a chemical process in which a substance reacts with oxygen to give off heat and light.
→ Fuel is a substance that gives off heat and light on burning.
→ Food is fuel to one’s body.
→ Fuels can be classified into solid, liquid, or gas fuels.
→ The substance which can burn to give light and heat are called combustible substances.
→ The non-combustible substance cannot react with oxygen on burning and cannot give light or heat.
→ Wood, Paper, Kerosene oil, Straw, Charcoal, Match sticks are combustible substances.
→ Iron nails, stone pieces, glass, etc. are non-combustible substances.
→ The lowest temperature at which a substance catches fire is called its ignition temperature.
→ The burning of various combustible materials requires different temperatures.
→ Inflammable substances are those substances that have very low ignition temperature and they easily catch fire with a flame.
→ Petrol, Diesel, LPG, alcohol are a few examples of inflammable substances.
→ Forest fire is very harmful.
→ Oxygen is necessary for combustion.
→ Three requirements for producing fire are:
- Presence of oxygen
- Presence of combustible substance
- Minimum ignition temperature of the substance
→ To control fire, one of the requirements for combustion is to be removed.
→ Water is mainly used to control fire as it lowers the ignition temperature.
→ Oil or petrol fire cannot be controlled by water as water is heavier than oil, it gets settle down below the oil and oil continues to burn.
→ Being a good conductor of electricity water is also not used in case of fires produced by short-circuiting.
→ Sand/soil is used to control fires caused by the burning of liquid fuels or electricity.
→ Fires can be controlled either by cutting off the supply of air or bringing down the ignition temperature or removing the combustible substance.
→ Different types of fire extinguishers are used to control fire.
→ Combustion is of many types such as Rapid combustion, Spontaneous combustion, Explosion.
→ Flame is formed by the burning of vapours or combustible substances.
→ The Blue non-luminous zone of the flame is the hottest part of the flame.
→ A luminous zone of flame usually contains unburnt particles of carbon.
→ The calorific value of a fuel is energy produced by the complete combustion of kg of the fuel.
→ The unit of calorific value in kilojoules per Kg (KJ/Kg).
→ No fuel is an ideal fuel.
→ The burning of fuels is caused by air pollution, health hazards, global warming, acid rains, etc.
→ Global warming is a slow rise in the temperature of the environment of the earth.
→ Nitrogen and Sulphur oxides produced by the burning of fossil fuels, dissolve in water to produce acid rains.
→ Acid rain is harmful to crops, buildings, and soil.
→ CNG is a clean fuel as it causes no air pollution.
→ Combustion: It is a chemical process in which a substance reacts with oxygen to give off heat and light.
→ Combustible Substance: The substance which on burning produces light and heat, is called a combustible substance.
→ Non-Combustible Substance: The substance which cannot produce light and heat and cannot react with oxygen on burning is called a non-combustible substance.
→ Ignition Temperature: The lowest temperature at which a substance catches fire, is called its ignition temperature.
→ Inflammable Substance: The substance which has low ignition temperature and catches fire easily.
→ Fire Extinguisher: A device used to control fire.
→ Combustion: The process of burning fuel to give light and heat.
→ Calorific Value: The energy produced by the complete burning of 1 kg of fuel.
→ Global Warming: The slow rise in temperature of the environment of the earth.