NCERT Solutions For Class 8 Science Chapter 4 Combustion And Flame LAQs

NCERT Solutions For Class 8 Science Chapter 4 Combustion And Flame Long Answer Questions

Question 1. List the conditions under which combustion can take place.
Answer:

Necessary conditions for combustion are as follows:

1. Presence of combustible substance.
2. Proper supply ofair to provide oxygen.
3. Attainment of ignition temperature

Question 2. Explain how the use of CNG in automobiles has reduced pollution in our cities.
Answer:

CNG has replaced diesel and petrol as fuel in automobiles because petrol and diesel produce a lot of unburnt carbon particles and emit carbon dioxide, nitrogen oxides, and sulphur dioxide.

These gases are all poisonous and cause various environmental hazards. The main causes of acid rain are nitrogen oxides and sulphur dioxide.

But CNG is safe because it produces these harmful substances in very small amounts. Thus, the use of CNG is reducing pollution in our cities.

NCERT Solutions for Combustion and Flame SAQs Class 8

Question 3. Compare LPG and wood as fuels.
Answer:

The Differences between LPG and wood are as follows:

Question 4. Give reasons.

1. Water is not used to control fires involving electrical equipment.
Answer:

Water is not used to control fires involving electrical equipment because it conducts electricity, which can cause dangerous electric shocks.

NCERT Solutions for Class 8 Science Combustion and Flame SAQs

2. LPG is a better domestic fuel than wood.
Answer:

LPG is a better domestic fuel than wood because LPG has more calorific value and produces pollution, while wood has less calorific value and produces smoke and causes more pollution.

3. Paper by itself catches fire easily, whereas a piece of paper wrapped around an aluminum pipe does not.
Answer:

It is because the ignition temperature of paper is lower, so it catches fire easily. It does not catch fire when wrapped around an aluminum pipe because aluminum absorbs the heat by conduction, so the paper does not attain its ignition temperature.

NCERT Solutions for Combustion and Flame Chapter 4 SAQs

Question 5. Make a labelled diagram of a candle flame.
Answer:

NCERT Class 8 Science Chapter 4 Combustion and Flame SAQs

Question 8. The table shows the calorific value and pollutants released by four types of fuels.

1. Which fuel can boil the water in a vessel the fastest?

1. Type 1
2. Type 2
3. Type 3
4. Type 4

Answer: 4. Type 4

2. Which fuel can cause acid rain on combustion?

1. Type 1 only
2. Type 4 only
3. Both type 1 and type 3
4. Both type 2 and type 4

Answer: 3. Both type 1 and type 3

Combustion and Flame Class 8 NCERT SAQs

3. Which fuel type is likely to be biogas?

1. Type 1
2. Type 2
3. Type 3
4. Type 4

Answer: 4. Type 4

Question 9. Give two examples encli for solid, liquid, and gaseous fuels along with some Important uses.
Answer:

Solid fuels include wood and coal. Wood is used to cook food in homes, and coal is also used in industries.

Liquid fuels Examples are kerosene and petrol. Kerosene is used in stoves and in lamps to cook food and petrol is used as a fuel in automobiles. Gaseous fuels Examples are natural gas and petroleum gas. These are used in industries, CNG is used to run automobiles.

Question 10. How can you burn wood or coal using kerosene oil?
Answer:

We have to use kerosene oil to start fire jn wood or coal. It is because coal has high ignition temperature.

A burning matchstick cannot produce sufficient heat to reach the ignition temperature of coal. Since, ignition temperature of kerosene oil is low, so ifsome kerosene is sprinkled over the wood, the kerosene starts burning by a lighted matchstick.

The heat produced by the burning of kerosene makes the wood to burn. The coal pieces are then placed over the burning wood. The large heat produced by the burning wood heats the coal to its ignition temperature. In this way, the coal starts burning.

Class 8 Science Chapter 4 Combustion and Flame Short Answer Questions

Question 11. What are the three essential requirements to produce fire? How fire extinguisher useful for controlling the fire?
Answer:

The three essential requirements to produce fire are as follows:

1. Fuel
2. Air and
3. Heat is required to acquire the ignition temperature.

NCERT Class 8 Science Chapter 4 Combustion and Flame SAQs

The job of a fire extinguisher is to cut off the supply fair or to bring down the temperature of the fuel or both. The most common fire extinguisher is water.

But water works only when things like wood and paper are on fire. For fires involving electrical equipment and Inflammable materials like petrol, carbon dioxide (CO) is the best extinguisher. CO2, being heavier than oxygen, covers the fire like a blanket. Since the contact between the fuel and oxygen is cut off, the fire can be controlled