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

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

Question 1. Two glass Jars, A and B, are filled with carbon dioxide and oxygen gases, respectively. In each jar, n lit candle is placed simultaneously. In which Jar, will the candle remain lit for a longer time, and why?
Answer:

In jar B, the candle remains lit for a longer time because oxygen is a supporter of combustion.

NCERT Solutions for Combustion and Flame VSAQs Class 8

Question 2. Why should we take special care in storing kerosene oil?
Answer:

We need to take special care in storing kerosene oil because it has low ignition temperature and it can catch fire easily.

Combustion and Flame VSAQs NCERT Solutions Class 8

Question 3. Anu wants to boil water quickly in a test tube. On observing the different zones of the flame, she is not able to decide which zone of the flame will be best for boiling water quickly. Help her in this activity.
Answer:

Anu should keep her test tube in the outermost zone or non-luminous zone of the flame because it is the hottest zone of a flame.

Question 4. Why is the use of diesel and petrol as fuels in automobiles being replaced by Compressed Natural Gas (CNG) in big cities?
Answer:

It is because CNG produces harmful products in very small amounts, and it is a clean fuel.

NCERT Solutions for Class 8 Science Combustion and Flame VSAQs

Question 5. What do you understand by fuel efficiency?
Answer:

Fuel efficiency is determined by its calorific value, which is the amount of heat energy produced on the complete combustion of 1 kg of a fuel. The calorific value of a fuel is expressed in KJ or kg.

Question 6. Name the unit in which the calorific value of a fuel is expressed.
Answer:

The Calorific value ofa fuel is expressed in kilojoules per kilogram (kJ/kg).

Question 7. Explain how CO2 can control fires.
Answer:

Carbon dioxide (CO2) is the best fire extinguisher. Being heavier than oxygen, it covers the fire like a blanket. Since the contact between the fuel and oxygen is cut-off and hence, the fire is controlled. It also brings down the temperature of the fuel.

NCERT Solutions for Combustion and Flame Chapter 4 VSAQs

Question 8. It is difficult to burn a heap of green leaves, but dry leaves catch fire easily. Explain.
Answer:

It is difficult to burn a heap ofgreen leaves because the green leaves contain some water, due to which the ignition temperature ofleaves increases and they do not catch fire easily, while dry leaves have no water, so they catch fire easily.

Combustion and Flame Class 8 VSAQs and Answers

Question 9. Which zone of flame does a goldsmith use for melting gold and silver, and why?
Answer:

A goldsmith uses the outer zone or non-luminous zone of a flame for melting gold and silver because it is the hottest zone of a flame and has more temperature.