A substance which reacts with oxygen giving heat is called a combustible substance. Which one of the following is a combustible substance?

1

(a)

Iron nail

(b)

Glass

(c)

Stone piece

(d)

Wood

Which one of the following has the highest calorific value?

1

(a)

Kerosene

(b)

Biogas

(c)

LPG

(d)

Petrol

If a person's clothes catch fire. The best way to extinguish the fire is to

1

(a)

throw water on the clothes

(b)

use fire extinguisher

(c)

cover the person with a woolen blanket

(d)

cover the person with a polythene sheet

Choose the incorrect statement from the following. Forest fires are usually due to

1

(a)

carelessness of humans

(b)

heat of Sun

(c)

cutting of trees

(d)

lightning strike

The calorific value of a fuel is expressed in a unit called

1

(a)

kilojoule per litre

(b)

kilogram per millilitre

(c)

kilojoule per gram

(d)

kilojoule per kilogram

In villages people use wood as fuel because

1

(a)

it is considered to be an ideal fuel

(b)

of its easy availability and low cost

(c)

it is environment friendly

(d)

it catches fire easily

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

1

(a)

proper combustion of fuel

(b)

improper cooking of potato curry

(c)

improper combustion of the fuel

(d)

burning of copper vessel

A ____________process in which a substance reacts with_________ to give off heat is called combustion.

1

(a)

chemical, oxygen

When the clothes of a person catch _______________the person is covered with a ___________to extinguish fire.

1

(a)

fire, blanket

The substances which vaporise during______________ give flame

1

(a)

burning

The lowest temperature at which a substance catches fire is called its _________________temperature.

1

(a)

ignition

Ignition temperature of __________________is lower than that of wood

1

(a)

petrol

The amount of heat energy produced on complete combustion of 1 kg of a fuel is called its___________________

1

(a)

calorific value

The type of combustion in which any substance starts to burn on its own is called_________________combustion.

1

(a)

spontaneous

Alcohol, CNG and LPG are inflammable substances.

1

(a) False

(b) True

Greater the calorific value. better is the fuel.

1

(a) False

(b) True

Middle zone is the hottest zone of a flame.

1

(a) True

(b) False

The substances which vaporise during buming give flame.

1

(a) False

(b) True

Sun produces heat and light due to nuclear reactions

1

(a) False

(b) True

The fuel can be in solid, liquid or in gaseous form.

1

(a) False

(b) True

How heat is produced in our body?

2

(a)

Give three examples of inflammable substances

2

(a)

Which type of substances produce flame? Does charcoal burn with flame?

2

(a)

Do all the substances catch fire at the same temperature?

2

(a)

Name the unit in which the calorific value of a fuel is expressed.

3

(a)

In an experiment 4.5 kg of a fuel was completely burnt. The heat produced was measured to be 180,000 kJ. Calculate the calorific value of the fuel.

3

(a)

Cracker on ignition produces sound. Why?

3

(a)

What should be done to control fire due to oil?

3

(a)

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

5

(a)

What are the three essential requirements to produce fire? How fire extinguisher is useful for controlling the fire?

5

(a)