AP 8th Class Physical Science Notes Chapter 10 Combustion and Flame
→ Acid Rain : The rain added with oxides of sulphur and nitrogen are called Acid rain.
→ Calorific Value : The amount of heat energy produced on complete combustion of 1 kg of a fuel is called its calorific value.
→ Combustion : A chemical process in which a substance reacts with oxygen to give off heat is called combustion.
→ Deforestation : Culting or firing of the trees is called deforestation.
→ Explosion : A large amount of gas formed in the reaction is liberated. Such a reaction is called explosion.
→ Flame : Burning of a vapour fuel is a flame.
→ Fire : Fire is a burning of a fuel in the presence of air.
→ Extinguisher : Extinguisher is a tool which is used to control the fire.
→ Fuel : The substance which undergo combustion is called a fuel.
→ Fuel Efficiency : Fuel efficiency of a fuel is expressed in its calorific value.
→ Global Warming : Global warming is the rise in temperature of the atmosphere of the earth.
→ Ideal Fuel : An ideal fuel is cheap, readily available, readily combustible and easy to transport. It has high calorific value. It does not produce gases or residues that pollute the environment.
→ Ignition Temperature : Ignition temperature is the lowest temperature at which a combustible substance catches fire.
→ Inflammable Substances : The substances which have very low ignition temperature and can easily catch fire with a flame are called inflammable substances.
→ The substance that undergoes combustion is said to be combustible. It is also called a fuel.
→ LPG, kerosene, coconut oil, wood, cow dung cakes, coal etc., are called fuels or combustible substances.
→ Oxygen (in air) is essential for combustion.
→ During the process of combustion, heat and light are given out.
→ Ignition temperature is the lowest temperature at which a combustible substance catches fire.
→ Different substances have different ignition temperatures. So, different substances catch fire at different temperatures.
→ A mixture of antimony trisulphide, potassium chlorate and white phosphorus with some glue and starch are present in the matchstick head.
→ The rubbing surface has powdered glass and a little red phosphorus.
→ The substances which have very low ignition temperature and can easily catch fire with a flame are called inflammable substances.
→ Examples of inflammable substances are petrol, alcohol, Liquified Petroleum Gas (LPG) etc.
→ Inflammable substances have very low ignition temperature.
→ Fire can be controlled by removing one or more requirements essential for producing fire.
→ Water is commonly used to control fires.
→ Water cools the combustible material so that its temperature is brought below its ignition temperature.
→ The three essential requirements for producing fire are fuel, air and heat. Fuel: burns itself; Air: to supply oxygen; Heat: to raise the temperature of the fuel beyond the ignition femperature.
→ Fire can be controlled by removing one or more of the following
- fuel
- air supply,
- heat requirements.
→ The type of combustion in which a material suddenly bursts into flames, without the application of any apparent cause is called spontaneous combustion.
→ The combustion in which the fuel burns rapidly and produces heat and light is known as rapid combustion.
→ When a cracker is ignited, a sudden reaction takes place with the evolution of heat, light and sound. A large amount of gas formed in the reaction is liberated. Such a reaction is called explosion.
→ For fires involving electrical equipment and inflammable materials like petrol, carbon dioxide (CO2) is the best extinguisher.
→ Spontaneous forest fires are sometimes due to the heat of the sun or due to lightning strike.
→ Water cannot be used to control fires involving electrical equipment or oils.
→ There are various types of combustions such as rapid combustion, spontaneous combustion, explosion etc.
→ There are three different zones of a flame-dark zone, luminous zone and non-luminous zone.
→ Different zones of candle flame and colours
- luminous zone : Outer zone of complete combustion (blue)
- non-luminous zone : Middle zone of partial combustion (yellow)
- dark zone; : Innermost zone of unburnt wax vapours (black)
→ An ideal fuel is cheap, readily available, readily combustible and easy to transport. It has high calorific value.
→ It does not produce gases or residues that pollute the environment.
→ Fuels differ in their efficiency and cost.
→ The amount of heat energy produced on complete combustion of 1 kg of a fuel is called its calorific value.
→ Fuel efficiency is expressed in terms of its calorific value which is expressed in units of kilojoule per kg.
→ Unburnt carbon particles in air are dangerous pollutants causing respiratory problems.
→ Incomplete combustion of a fuel gives poisonous carbon monoxide gas.
→ Increased percentage of carbon dioxide in air has been linked to global warming.
→ Oxides of sulphur and nitrogen produced by the burning of coal, diesel and petrol cause acid rain which is harmful for crops, buildings and soil.
→ Combustion of fuels release fine dust particles, carbon monoxide, carbon dioxide, sulphur dioxide etc.
→ The carbon monoxide gas produced is very dangerous, can kill persons.
→ Increased concentration of carbon dioxide in the air is believed to cause global warming.
→ The sulphur dioxide gas is an extremely suffocating and corrosive gas.
→ The acid rain is very harmful for crops, buildings and soil.
→ Increased concentration of carbon dioxide in the air is believed to cause global warming.