Lakhmir singh solutions science class 8 Solutions for Chapter 6 combustion and flame

Define the ignition temperature of a substance.

Which of the two has a lower ignition temperature: petrol or kerosene?

Name the most common fire extinguisher.

Which is the best fire extinguisher for fires involving electrical equipment and inflammable materials like petrol?

Name one substance which undergoes spontaneous combustion (or burns in air at room temperature).

Name the unit in which the calorific value is expressed.

Which of the following fuels has the lowest calorific value? Diesel, Methane, Coal, CNG, Petrol

Which of the following fuels has the highest calorific value? Diesel, Methane, CNG, Coal, Petrol

Name the term which is used to express the efficiency of fuel.

Name one solid, one liquid, and one gas which burns by producing a flame.

Which of the following does not produces a flame on burning? Camphor, Charcoal, Kerosene

Name one fuel that burns without producing a flame.

How many zones are there in a flame?

Which zone of a candle flame is the hottest?

In a candle flame, what is the colour of (a) innermost zone (b) middle zone, and (c) outer zone?

Name any harmful product released by the burning of fuels.

Name the very poisonous gas produced by the incomplete combustion of fuels.

Name the fuel which is gradually replacing petrol and diesel in automobiles.

Name two substances having low ignition temperature and two having high ignition temperatures.

Fill in the blanks with suitable words

(a)A fuel must be heated to its____ before it starts burning.

(b)The most common supporter of combustion around us is ____

(c)The fire produced by burning oil cannot be controlled by____

(d)A liquid fuel used in homes is____

(e)The amount of heat evolved when 1kg of fuel is burnt completely is called its____

(f)The substance which vaporize during, give____

(g)Burning of wood and coal causes____ of air.

(a) What are fuels? Name any two common fuels.

(b)State any four characteristics of an ideal fuel (or good fuel).

(a) Define the calorific value of a fuel.

(b)“The calorific value of LPG is 55000KJ/kg”. What does it mean?

Can you burn a piece of wood by bringing a lighted matchstick near it? Explain.

Why do you have to use paper or kerosene oil to start a fire in wood or coal?

What is meant by rapid combustion? Give one example of rapid combustion.

What is meant by spontaneous combustion? Give one example of spontaneous combustion.

What is meant by explosive combustion (or explosion)? Give one example of explosive combustion (or explosion).

How will you show that air is necessary for combustion?

Can the process of rusting be called combustion? Give a reason for your answer.

Why are fires produced by burning oil not extinguished by pouring water?

Explain why fire caused by electricity should not be extinguished by pouring water.

How is the fire caused by electricity extinguished?

How is the fire produced by burning oil (or petrol) extinguished?

A drum full of kerosene catches fire. What is the simplest way to put off this fire?

What is the first thing you should do if a fire caused by burning wood or paper?

(a) What does a Fire Brigade do when it arrives at a place where a building is on fire.

(b)Describe one method of putting out a fire caused by burning wood or paper.

Explain why, we are advised not to sleep in a room having closed doors and windows, with a coal fire burning inside.

(a) What is a flame? What type of substance, on burning, gives a flame?

(b)What is the difference between the burning of a candle and the burning of fuel like coal?

How does pouring water extinguish a fire?

Explain how carbon dioxide is able to control fires?

If you see a person whose clothes are on fire, how will you extinguish the fire? Give a reason for your answer.

Give two examples each of (a) solid fuels (b) liquid fuels (c) gaseous fuels

Name the various zones of a candle flame. Which zone(or part) of a candle flame is the least hot(or coldest)?

Why does a goldsmith blow air into the kerosene lamp flame with a blow-pipe?

In which zone of a candle flame: (a) partial combustion of fuel takes place, and (b) complete combustion of fuel takes place?

Explain how the use of CNG in automobiles has reduced pollution in cities.

What is the disadvantage of burning wood as fuel?

Give reasons for the following: LPG is a better domestic fuel than wood.

Explain why, when a burning candle is covered with an inverted gas jar, the candle gets extinguished after some time.

It is difficult to burn a heap of green leaves but dry leaves catch fire easily. Explain.