CBSE Class 8 Science Revision Notes Chapter 6

Class 8 Science Revision Notes Chapter 6

CBSE Class 8 Science Revision Notes Chapter 6 – Combustion and Flame 

Class 8 Science Chapter 6 Notes provided by Extramarks are prepared by subject matter experts to help students to prepare the topics covered in the chapter. These revision notes will also help them prepare for other competitive exams. Students can access these Class 8 Chapter 6 Science Notes from Extramarks’ website and refer to them for a thorough and clear understanding of the chapter’s content so that they can answer any question during exams without being hassled. These revision notes are written according to the revised  . Key concepts of the chapter are covered in a simple and easily understandable format.

Revision Notes for CBSE Class 8 Science Chapter 6

Access Class 8 Science Chapter 6 – Combustion and Flame Notes 

Extramarks notes will be a student’s last-minute revision guide providing all the necessary information in a nutshell, to revise the entire syllabus quickly and easily.

Here are some of the key concepts  mentioned in the chapter:

1. Combustion:

When a substance undergoes a chemical reaction in the presence of air (oxygen) to produce light and heat, the process is known as combustion.

Hence, the presence of oxygen is necessary for combustion and it cannot take place in its absence. The substance undergoing combustion is known as a combustible substance.

Types of Combustion 

There are many types of combustion and the type of combustion depends upon the type of fuel used. Based on nature and intensity, combustion is of three types:

1. Rapid Combustion: A combustion is said to be rapid combustion when a substance burns rapidly and produces light and heat. For example, the burning of a gas stove, matchstick, etc.
2. Spontaneous Combustion: When a material suddenly bursts into flames, even without any application of apparent cause, such type of combustion is called spontaneous combustion. For example, burning of camphor, burning of phosphorus, etc.
3. Explosion: When a large amount of gas formed in the reaction is liberated, such a reaction is known as an explosion. For example, missiles,  firecrackers, etc.

2. Flame:

A zone or burning vapour caused by substances during the process of combustion is called flame. For instance, LPG gas, Kerosene oil, coal etc.

3. Fuel:

Any substance that obtains an energy that can be used to heat or move another object on undergoing combustion is known as fuel.

Property of a Good Fuel:

The properties of a good fuel are as follows:

• It must be readily available.
• It must be cheap.
• It must burn easily at a moderate rate.
• It should have a high calorific value.
• After combustion, it must not leave behind any undesirable substances.

The calorific value of a fuel is used to describe its efficiency. The quantity of heat energy generated during the complete combustion of 1 kilogramme of fuel is referred to as calorific value, which is measured in terms of kilojoules per kg (kJ/kg).

Types of Fuels:

1. Solid Fuels: Combustible substances that are solid at room temperature are known as solid fuels. Examples of solid fuel include camphor, wood, coal, charcoal etc.
2. Liquid Fuels: Liquid Fuels are volatile liquids which produce combustible vapour. Such fuels are widely used fuels in vehicles. Examples of liquid fuels include petrol, kerosene, diesel etc.
3. Gaseous Fuels: Gaseous fuels are combustible gases or a mixture of combustible gases. Examples of such fuels include LPG, CNG, propane, biogas etc.

Harmful Effects of Burning of Fuels:

• Fuels that contain carbon, such as wood, coal, or any other fossil fuel, produce unburned carbon particles known as suits. These are harmful pollutants because they can lead to cancer and respiratory illnesses like asthma.
• A poisonous gas, carbon monoxide, is produced during the incomplete combustion of carbon fuels. Prolonged exposure to this gas is fatal.
• Global warming is caused by an increase in the atmospheric concentration of carbon dioxide. The greenhouse effect is a phenomenon caused by an increase in the amount of carbon dioxide in the atmosphere.
• Sulphur oxides and nitrogen oxides dissolve in rainwater and form acids. Such rain is referred to as acid rain. It is extremely harmful to buildings, crops, and soil, as it corrodes the metal surface faster and increases the acidity of the soil.

Notes of Combustion and Flame Class 8 Download 

Extramarks provides authentic Chapter 6 Science Class 8 Notes which adhere to the NCERT book and follow the CBSE syllabus that students can use to improve their exam preparations. Students can access these notes at any time and continue their studies uninterrupted, without worrying about their exams, since they are easily available on  Extramarks’ website. Learning becomes seamless as materials for all the chapter’s topics are available at one place. Students need not browse through other sites because Extramarks has a repository of study materials for all subjects, syllabi as well as question papers, sample papers etc. to provide foolproof preparation ahead of exams.

Combustion, Fuels and Flames Class 8 Notes 

Subject matter experts have written the Class 8 Science Notes Chapter 6 in a concise and structured manner that makes the concepts easier to understand and remember.  All topics in these notes are covered in detail.

Extramarks notes will be a student’s last-minute revision guide providing all the necessary information in a nutshell, to revise the entire syllabus quickly and easily.

Here are some of the key concepts  mentioned in the chapter:

Combustion:

The process of combustion is the release of light and heat as a result of compounds reacting chemically with oxygen. Burning wood is one such example of combustion.

Combustible Substances 

The substances that easily catch fire are known as combustible substances. Examples of combustible substances are paper, wood, etc.

Non-Combustible Substances 

The substances that do not catch fire readily are known as non-combustible substances. Examples of non-combustible substances are sand, water, etc.

Fuels 

Those substances which produce energy on combustion are known as fuels. Fuels can be obtained both artificially or naturally in the form of solid, liquid, or gas. Fossil fuel, nuclear energy, etc. are some examples of fuel.

Ignition Temperature 

The minimum temperature at which a particular substance catches fire is known as the Ignition Temperature.

Inflammable Substances 

These substances that have low ignition temperatures and easily catch fire are known as inflatable substances. Examples of such substances are acetone, diesel, etc.

Fire:

A chemical combustion process between fuel and oxygen causes fire. The quantity of fuel and oxygen available determines how long the fire will burn.

Fire Triangle 

Three things are essential for the production of fire:

• Combustible or fuel substance
• A heat source that will help in raising the temperature to the ignition temperature.
• Ample amount of oxygen to sustain the combustion

In the case of the absence of the above-mentioned elements, fire does not take place.

Candle Flame 

A flame is the visible part of the fire, which contains gases.

Zones of Candle Flame 

• The outer zone of flame is the hottest part of the flame and undergoes complete combustion. It is non-luminous and blue.
• The middle zone of the flame is moderately hot and undergoes partial combustion. It is the brightest part of the candle flame.
• The innermost zone of the candle flame contains unburnt wax vapours and is black.

Smoke 

The unburnt particle present in solid form and dispersed in the air is smoke. It appears black due to the unburnt carbon particles present in it.

Types of Combustion 

It is of two types:

• When both heat and light are released in a brief period during combustion, it is called rapid combustion. LPG combustion is an example of rapid combustion.
• When substances catch fire spontaneously without any heat and happen on their own, it is called spontaneous combustion. For example, forest fires.

Calorific Value of Fuel 

The amount of heat energy produced on complete combustion of 1kg of fuel is known as the Calorific Value of Fuel. Kilojoule/kilogram (kJ/kg) is the expression for calorific value.

Efficiency of Fuel 

The amount of energy released in fuel combustion put into practical work is known as the efficiency of fuel.