Check the below Online Education NCERT MCQ Questions for Combustion and Flame Class 8 Extra Questions and Answers Science Chapter 6 Pdf free download. https://ncertmcq.com/extra-questions-for-class-8-science/
Online Education for Class 8 Science Chapter 6 Extra Questions and Answers Combustion and Flame
Combustion And Flame Class 8 Questions And Answers Question 1.
Why is food called fuel for our body?
In our body, food is broken down by reaction with oxygen and heat is produced. That is why food is called fuel for our body.
Class 8 Combustion And Flame Question Answer Question 2.
Why does a piece of wood not burn by bringing a burning matchstick near it?
Wood has high ignition temperature. A burning matchstick cannot produce so much heat to reach the ignition temperature of wood. Therefore, wood does not burn.
Combustion And Flame Question Answer Question 3.
Why is it important for all of us to know the telephone numbers of the fire service station?
Who knows when and where suddenly fire breaks out. The fire brigade from the fire service station could be called when fire occurs anywhere. This can be -done only when we know the telephone numbers of fire- services.
Combustion And Flame Class 8 Question Answer Question 4.
How can the fire caused by burning liquid fuels be extinguished?
It can be extinguished by throwing sand or soil over it.
Class 8 Science Chapter 6 Short Question Answer Question 5.
Name two types of fire extinguishers.
Soda acid fire extinguishers and hydrocarbon fire extinguishers are two types of fire extinguishers.
Combustion And Flame Class 8 Questions Answers Question 6.
Name a substance which burns itself in air.
Combustion And Flame Class 8 Learn Insta Question 7.
Does charcoal produce a flame on burning?
No, charcoal does not vaporise and so does not produce a flame.
Combustion And Flame Class 8 Question 8.
Which gas is formed during the incomplete combustion of any fuel?
Carbon monoxide gas.
Combustion And Flame Class 8 Solutions Question 9.
Define calorific value of fuel.
Calorific value: The amount of heat energy produced on complete combustion of 1 kg of a fuel is called its calorific value. The calorific value of. a fuel is expressed in a unit called kilojoule per kg (kJ/kg). An ideal fuel has high calorific value.
Class 8 Science Chapter 6 Combustion And Flame Question Answer Question 10.
Define ignition temperature.
Ignition temperature is the lowest temperature at which a combustible substance catches fire. An ideal fuel should have a proper ignition temperature.
Class 8 Science Chapter Combustion And Flame Question 11.
Define combustible and non-combustible substances.
The substance that undergoes combustion is said to be combustible.
The substance that does not undergo combustion is called non-combustible.
Extra Questions For Class 8 Science With Answers Question 12.
Define ignition temperature. Do all combustible substances have same ignition temperature?
The lowest temperature at which a substance catches fire is called its ignition temperature.
All combustible substances do not have same ignition temperature. In fact, each combustible substance has i different ignition temperature.
Ncert Science Book Class 8 Extra Questions With Answers Question 13.
Does combustible substance catch fire on its own? Why?
A combustible substance does not catch fire or bum on its own. It is so because a combustible substance does not catch fire as long as its temperature is lower than its ignition temperature.
Extra Question Of Class 8 Science Question 14.
Define spontaneous combustion.
The type of combustion in which a material suddenly bursts into flames without the application of any apparent cause is called spontaneous combustion, e.g., combustion of coal dust.
Combustion And Flame Class 8 Pdf Download Question 15.
What causes fires in coal mine?
Spontaneous ‘combustion of coal dust results in many disastrous fires in coal mines.
Class 8 Science Chapter 6 Question Answer Question 16.
What leads to deforestation? What is its effect?
Cutting of trees leads to deforestation. It is quite harmful as it leads to global warming.
Is there any ideal fuel? If not, what is the alternative?
There is probably no fuel that could be considered as an ideal fuel. We should, as an alternative, look for a fuel which fulfils most of the requirements for a particular use.
What is global warming? What causes it?
The increase in temperature of earth’s atmosphere is termed as global warming.
The excess increase of carbon dioxide in atmosphere causes global warming because carbon dioxide facilitates greenhouse effect, i.e., carbon dioxide traps hot radiations emitted by the earth’s surface.
What is done to extinguish fire due to burning of oil or petrol?
Fire produced by burning of oil or petrol can be controlled by throwing sand or soil over it.
What is flame?
When a fuel is burned, a hot luminous gas emerges out of the burning fuel. This gas is called flame. Flames are a result of the substances which vaporize on burning. Example includes kerosene oil, wax, etc. which form flames on burning.
Explain greenhouse effect. Mention any two greenhouse gases.
Greenhouse effect is warming of earth’s surface and atmosphere due to trapping of sun’s heat by certain gases in the earth’s atmosphere. Water vapour, carbon dioxide, methane and certain other gases in the air are responsible for the Greenhouse effect of those gases, water vapour has the largest effect.
What is the role of water in extinguishing fire?
Water cools the combustible material, so that its temperature is brought below its ignition temperature. This prevents the fire from spreading. Water vapours also surround the combustible materials helping in cutting the supply of air. So, the fire is extinguished.
Why can we not use water to extinguish fire that is caused due to burning of oil or petrol?
When water is used to extinguish fire due to burning of oil/petrol, water being heavier than oil/petrol settles down below it and it continues to burn. That is why we cannot use water to extinguish fire in such a situation.
What would you do in case of fire produced by electric short circuit?
In the case of fire caused by electric short circuit, water is not used at all because it is a conductor of electricity and may cause electrocution or electric shock. The only solution is to cut off the supply of electricity and then use the spray of water on the flame to extinguish fire or use fire extinguisher.
What is the working methodology of fire extinguisher?
Fire extinguisher functions in one of the following ways :
- either it cuts off supply of air to the combustible substance.
- or it brings down the temperature of the combustible substances well below its ignition temperature.
What are the causes of forest fires? How can it be kept under control?
Forest fires sometimes occur due to the heat of the sun. However, most forest fires are due to the carelessness of human beings. So, it is important to remember that the campfires must be completely extinguished before leaving a forest after a picnic or any visit and people should not throw any burning thing in the forest.
What do you mean by explosion? How does it take place?
Explosion is a sudden reaction in which heat, light, sound and large amount of gas is evolved. Explosion can also take place if pressure is applied on the cracker or any other combustible material kept in large amount.
What are the characteristics of an ideal fuel?
The characteristics of an ideal fuel are:
- It should be readily available,
- It should be cheap,
- It should bum easily in air at a moderate rate,
- It should produce a large amount of heat, and
- It should not leave behind any undesirable substances.
What are the disadvantages of burning wood in a chulha?
Disadvantages of burning wood in a chulha are :
- It produces a lot of smoke, which causes respiratory problems.
- Burning of wood leaves behind ashes, which are undesirable substances.
- Cutting of wood for fuel leads to deforestation.
What are the disadvantages of global warming?
Global warming causes the rise in temperature of the atmosphere of the earth. This leads to melting of polar glaciers resulting into rise in sea level and causing floods in the coastal areas.
What is the function of a fire extinguisher? Describe various types of fire extinguishers.
Fire extinguishers either cut off supply of air to the combustible substance or it brings down the temperature of the combustible substance well below its ignition temperature.
There are various types of fire extinguishers used for controlling fire :
- Soda acid fire extinguishers: It is based on the principle of cooling the fire. Carbon dioxide is liberated along with water. Water puts off the fire by lowering the temperature of the combustible material below its ignition temperature and carbon dioxide cuts off the supply of air to the combustible substances.
- Hydrocarbon fire extinguishers: It is based on the principle of covering burning material and cut off of oxygen supply to the fire. In this fire extinguisher, sodium bicarbonate comes out under pressure in the form of a foam. The foam covers the whole surface of oil. It cuts off the supply of air and the fire is controlled.
What are the harmful effects of fuel consumption on the environment? Describe.
The increasing fuel consumption has the following harmful effects on the environment.
- Carbon fuels like wood, coal, petroleum release unburnt, carbon particles. These particles are dangerous pollutants causing respiratory diseases, such as asthma.
- Incomplete combustion (combustion in insufficient supply of oxygen or air) forms carbon monoxide gas. It is a very poisonous gas.
- Combustion of most fuels releases carbon dioxide in the environment. Increased percentage of carbon dioxide in the air is believed to cause global warming.
- Burning of coal and diesel releases sulphur dioxide gas. It is an extremely Suffocating and corrosive gas.
- Petrol engines are responsible for the formation of nitrogen oxide gas.
Multiple Choice Questions (MCQs)
1. From the following the ideal fuel is