Class 8 Combustion and Flame

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Class 8 Combustion and Flame

Have you ever watched fire? Doesn’t it fascinate you? Or, if not fire, then you must have noticed a candle burning. Have you ever thought of watching the flame of the candle and must ponder about how it’s burning and about the structure of its flame? We know that science is that subject which has the answer to all your “why’s”. Hence, we are here with yet another chapter of science and its study notes to help our young audience and readers. In this blog, we will be providing you with important study notes of the chapter of the science of Class 8 Combustion and Flame. So if you are eager to know more about Class 8 Combustion and Flame, then read this blog till the end. 

Combustion 

Let us start this blog on class Class 8 Combustion and Flame notes by understanding the meaning of the term combustion. According to the chapter of Class 8 Combustion and Flame, when a substance reacts with oxygen, it produces heat, which is referred to as combustion. A combustible substance is any material that may burn or undergo combustion. A combustible substance is also known as fuel. Things like petrol, diesel, and other fuels are some of the examples of combustible substances. The fuel could be solid, liquid, or gaseous. During combustion, light may be emitted in the form of a flame or a glow.

Different Types of Combustion 

As per the chapter of Class 8 Combustion and Flame, there are 3 different types of combustion which are explained in the table provided below:

Spontaneous Combustion Substances spontaneously burst into flames for no apparent cause in this form of combustion.Example: coal dust in coal mines 
Rapid Combustion The substances burn quickly in this form of combustion, producing light and heat.Example: matchstick near stove or candle 
Explosion This form of combustion produces fire, light, and sound all at the same time. Furthermore, a large amount of gas is released.Example: firecrackers 
Class 8 Combustion and Flame
Credits: edurev.in

Also Read: Class 8 Science

Necessary Things For Combustion to Take Place

According to the chapter of class 8 Combustion and Flame, there are 3 major things that are required in order for combustion to take place. These are:

  • Air or oxygen 
  • Fuel or any other combustible substance 
  • Temperature above the ignition temperature of the substance
Class 8 Combustion and Flame
Credits: grc.nasa.gov

Ignition Temperature

According to the chapter of Class 8 Combustion and Flame, the minimum temperature at which any substance can catch fire is known as its ignition temperature. If the temperature of combustible material is below that of the combustion temperature, the substance will not burn or catch fire. Let us look at some real-life examples: cooking oil catches fire when a frying pan is left on a hot stove for too long, kerosene oil and wood do not catch fire on their own at room temperature, but if kerosene oil is heated a little, it will catch fire instantly. On the contrary, even though wood is slightly heated, it will not catch fire.

What is Inflammable Substance?

After knowing and getting a fair idea about the ignition temperature, let us now revise what is an inflammable substance. As per the chapter of Class 8 Combustion and Flame, inflammable substances are products that have a low combustion temperature and quickly catch fire. Petrol, LPG, and other fuels are some of the examples of inflammable substances.

Also Read: Science Projects for Class 8

Measures to Control Fire

Let us take our blog on class 8 Combustion and Flame notes further and revise/learn certain basic yet important measures to control fire. 

Measures  Description 
Fire Brigades  In the event of a fire, firefighters and fire brigades will put out the flames by sprinkling water on the affected areas. The water will lower the temperature below the temperature at which it will burn. As a result, the fire will be brought to a halt. Water vapour also envelops the combustible element, assisting in the cutoff of air supply. As a result, the fire has been put out.
Fire Extinguishers The most popular fire extinguisher is water. However, it only operates on
natural materials such as wood and paper. However, if a fire occurs near electrical equipment, water, which is an excellent conductor of electricity, will damage the equipment. In the event of a fire caused by gasoline, gas, or other flammable materials, even in that case or scenario, the water is ineffective. Carbon dioxide (CO2) is the safest extinguisher in such conditions. This extinguisher cuts off the air supply, lowering the temperature below the ignition temperature, effectively extinguishing the fire. Furthermore, it seldom causes damage to electrical equipment.
Blankets  If an individual sets fire to themselves, blankets may be used to put out the flames.

Do You Know: If the temperature rises too high in the summer, the regions with dry grasses catch fire in the woods and dry fields, which are known as forest fires. This fire easily spreads from grasses to trees, ultimately engulfing the entire forest. And putting out such fires is difficult.

Fire Precautions
Credits: foodalert.com

Flame 

Let us go a step further in our blog which is on Class 8 Combustion and Flame. After knowing everything related to combustion, let us now know something about flame. In simple words, when something is burned, hot, luminous gas is released from it. Flame is the name given to this gas which is released. Flames are caused by compounds that evaporate as they burn. Kerosene oil, wax, and other flammable substances are examples.

Also Read: NCERT Class 8 SST Syllabus

Structure of the Flame 

According to the chapter of Class 8 Combustion and Flame, the structure of flame can be bifurcated into 3 different zones namely: 

Outermost Zone  It is blue in colour and is the hottest of all the regions. In this part,
complete combustion takes place.
Middle Zone  It has a yellow colour and is very hot. Partial combustion
occurs in this zone.
Innermost Zone  It has the darkest colour and is the coolest of all the regions.

Also Read: NCERT Class 8 Maths Syllabus

Fuel 

As per the chapter of class 8 Combustion and Flame, any substance that undergoes combustion is called or known as fuel. Examples of fuels can be wood, charcoal, petrol, kerosene, etc. Let us now know about the characteristics of good fuel, fuel efficiency and ideal fuel. 

Fuel
Credits: protea.ltd.uk
Characteristics of good fuel Fuel Efficiency Ideal Fuel
It should be easily accessible. It should be inexpensive. It should be able to produce a lot of heat. After combustion, it does not produce any waste. An ideal fuel is one that meets all of the characteristics of good fuel, and it is impossible that such a fuel exists. The calorific value of a fuel is the amount of heat emitted per kilogram of fuel burned.The kilojoule per kilogram (kj/kg) is its unit.

Calorific Value Chart of Different Fuels

Fuel Calorific Value (kJ/kg)
Wood 17000 – 22000
Cow dung cake 6000 – 8000
Petrol 45000
Coal 25000 – 33000
Kerosene 45000
Diesel 45000
Hydrogen 150000
Biogas 35000 – 40000
LPG 55000
CNG 50000
Methane 50000

Also Read: List of NCERT Books Class 8

This brings us to the end of our blog on Class 8 Combustion and Flame notes. We hope that our young and brilliant readers must have revised and learned all the important topics of this chapter and are ready to fetch some extra marks in their science exams. For more such amazing reads and awesome study notes, stay in touch with Leverage Edu. 

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