Fire

Q.

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

Q. Your LPG gas stove at home is giving yellow flame.What can this mean?explain.

Q. how does a sodium carbonate extinguisher work? can it be used to put off electric fires?

Q. Why do fire brigades pour water on the fire?

1. Water cools the combustible material so that its temperature is brought below its ignition temperature.
2. This prevents the fire from spreading.
3. Water vapours help in cutting off the supply of air.
4. All of the above

Q.

Define the term burning.

Q. The best fire extinguisher for inflammable materials is:

1. Water
2. CO
3. 
4. 

Q. Forest fire produces a lot of air pollution. Write in brief about the reasons for forest fires.​

Q.

why water is not able to extinguish the fire which is set up by sodium?

Q. Choose the incorrect statement from the following.​

Forest fires are usually due to:​

1. carelessness of humans​
2. heat of sun​
3. cutting of trees​
4. lightning strike​

Q.

Fill in the following 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) Fire produced by burning oil cannot be controlled by___

(d) A liquid fuel used in homes is___

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

(f) The substances which vaporise during burning, give___

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

Q.

Soda acid fire extinguishers contains :a) sodium carbonate

B) sodium hydrogen carbonate , sulphuric acid

C) sodium carbonate, hydrochloric acid

D )sodium hydrogen carbonate, hydrochloric acid

Q.

How does a blanket help in extinguishing fire? Can a blanket be used to cut off electrical fire? [3 MARKS]

Q.

Which property of sand is used in extinguishing fires?

1. Non-inflammability

2. Flammability

3. Porosity

4. Low specific heat capacity

Q.

Fire is the result of which chemical reaction?

Q.

Based upon the type of fire, extinguishers are chosen. Explain the different types of fires. [5 MARKS]

Q. Fill in the blanks.​
(a) Burning of wood and coal causes ______ of air. ​
(b) A liquid fuel, used in homes is ______.
(c) Fuel must be heated to its ______ ______ before it starts burning.
(d) Fire produced by oil cannot be controlled by ______.

Q. Which of the following is not a combustible substance?​

1. camphor​
2. glass
3. straw
4. alcohol

Q.

Water works as a fire extinguisher by removing

1. only heat

2. only oxygen

3. heat and oxygen

4. the source of combustible substance.

Q. Air is necessary for burning as it supplies oxygen which is essential for combustion.

1. True
2. False

Q.

______is the second-largest component of air, constituting almost $21\%$ volume of air.

Q. Which of the following is the most common and accessible fire extinguisher?

1. Nitrogen
2. Carbon dioxide
3. Water
4. Oxygen

Q.

How does dumping water on fire extinguish it?

1. Water cuts the supply of oxygen

2. Water cools the burning fuel below the ignition point

3. Water cuts the supply of oxygen and water cools the burning fuel below the ignition point

4. Water supports the fire

Q.

When a substance is in vicinity of a fire, it will absorb some energy released from the fire.

1. The same amount of heat

2. Manish will have to give more heat compared to Gautam

Q. Choose the incorrect reason from the following.
Forest fires are usually due to:

1. carelessness of humans
2. cutting of trees
3. lightning strike
4. heat of sun

Q. Forest fire produces lot of air pollution. Write in brief about the reasons of forest fires.

Q. Fire undergoes a chemical reaction known as ___.

Q.

Which property of sand is used in extinguishing fires?

1. Low specific heat capacity

2. Porosity

3. Flammability

4. Non-inflammability

Q. Question 15
Shyam was cooking potato curry on a chulha. To his surprise, he observed that the copper vessel was getting blackened from outside. It may be due to:

(a) proper combustion of fuel
(b) improper cooking of potato curry.
(c) improper combustion of the fuel.
(d) burning of copper vessel.

Q. Water works as a fire extinguisher by removing

1. heat
2. oxygen
3. heat and oxygen

Q. Question 10
Choose the incorrect statement from the following. Forest fires are usually due to:

(a) carelessness of humans
(b) heat of sun
(c) cutting of trees
(d) lightning strike