The following Topics and Sub-Topics are covered in this chapter and are available on MSVgo:
We are familiar with different kinds of fuels– petrol and diesel used in automobiles, LPG and coal used to cook, charcoal, cow dung, etc. All these fuels burn to give heat energy used to perform different activities at home and in industries.
The chemical process in which a substance reacts with oxygen to give off heat and light is called combustion. The simple process of burning wood is an example of combustion. For combustion to occur, air is necessary. Try putting a candle under a glass jar with no supply of free air. You will notice that the candle burns only until there is oxygen in the jar.
You would have noticed that not all substances catch fire at the same temperature. Think of a matchstick, forest fires, or piece of paper. The lowest temperature at which a substance catches fire is called its ignition temperature.
Substances with very low ignition temperature can catch fire very easily and are called inflammable substances. Some examples of inflammable substances include petrol, LPG, diesel, etc.
We have all seen fire being put out by water in movies and TV shows. What exactly does water do to fire?
You may have noticed how different substances burn in different ways. Based on this, there are two different types of combustion:
Substances that burn rapidly to give heat and light are said to show rapid combustion.
Some substances catch fire suddenly, without any apparent cause, and are said to show spontaneous combustion. A great example of this type of combustion is substances like phosphorus that catch fire at room temperature.
Chemical Reaction and Combustion
Another example of combustion is the explosion of a cracker. When we ignite a cracker, a chemical reaction takes place inside it that leads to the combustion of substance inside and results in the liberation of a large amount of gas, along with heat and light. This type of reaction is called an explosion.
The flame is the visible, gaseous part of a fire. It is the light energy emitted during the process of fuel combustion. Substances that vaporize during burning give out flames—for example, kerosene and wax. Substances like coal that do not evaporate on burning do not give our flames while burning.
Structure of Flame
Did you know a candle flame has many zones? Observe a goldsmith. You will notice how he blows into the outermost zone of the flame. This is because the outermost zone of the flame is the hottest part of the flame.
Different zones of a candle flame are:
Substances that are used to generate energy for domestic and industrial purposes are called fuels. Commonly used fuels are petrol, diesel, kerosene, LPG, coal charcoal, etc.
Another property of fuels that makes them more or less popular is their efficiency.
We are all aware that the burning of fuels is harmful to us and our environment.
1. What is the difference between combustion and flame?
The chemical process by which a substance reacts with oxygen in the air to give out heat and light is called combustion. A flame, however, is the visible gaseous portion of the fire.
2. What type of combustion is fire?
Fire is an example of rapid combustion as it is characterised by the release of large amounts of heat and light in the form of a flame.
3. What are the 3 types of combustion?
Based on the nature of the process, combustion is of three types:
4. What is a flame in chemistry?
The flame is the visible gaseous portion of the fire. It is made up of three layers– with the outermost layer being the hottest and the innermost being least hot.
5. What are the 2 types of combustion?
Two types of combustion are rapid and spontaneous combustion. Rapid combustion is when a substance burns to release large amounts of heat and light. A substance that burns in the air without an apparent cause is said to show spontaneous combustion.
6. Does charcoal burn with a flame?
Charcoal does not burn with a flame because it does not evaporate on burning. It is notorious for leaving an unburnt residue that causes air pollution and respiratory diseases.
Every day, we see and use the combustion of fuels and substances, and this process is a part of our daily lives. However, when it comes to the combustion of fuels that are causing air pollution, we must switch to cleaner fuels like CNG as it produces very little by-products on combustion.