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

On placing an inverted tumbler over a burning candle. the flame extinguishes after sometime. This is because of non-availability of

1

(a)

oxygen

(b)

water vapours

(c)

carbon dioxide

(d)

wax

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

The substance expected to have the highest ignition temperature out of the following is

1

(a)

kerosene

(b)

petrol

(c)

coal

(d)

alcohol

Choose the incorrect statement from the following: A good fuel is one which:

1

(a)

is readily available

(b)

produces a large amount of heat

(c)

leaves behind many undesirable substances

(d)

burns easily in air at a moderate rate.

Burning of wood and coal causes___________ of air.

1

(a)

pollution

A liquid fuel, used in homes is___________

1

(a)

kerosene

Fuels differ in their _______ and _______.

1

(a)

Efficiency, cost

Incomplete combustion of a fuel gives poisonous _________ gas.

1

(a)

carbon monoxide

________ is the rise in temperature of the atmosphere of the earth.

1

(a)

Global warming

Alcohol, CNG and LPG are inflammable substances.

1

(a) False

(b) True

The substances which vaporise during buming give flame.

1

(a) False

(b) True

Food is a fuel for our body.

1

(a) False

(b) True

Increased concentration of nitrogen in air is believed to cause global warming.

1

(a) True

(b) False

The substances which vaporize during burning, give flame.

1

(a) False

(b) True

What is combustion?

1

(a)

A chemical process in which a substance burns in the presence of oxygen to release heat is called combustion.

What happens when charcoal burns in the air?

1

(a)

Charcoal bums in air producing carbon dioxide, heat and light.

Define ignition temperature.

1

(a)

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

Name different zones of flame.

1

(a)

Three zones of a flame are :
(i) Non-luminous zone.
(ii) Luminous zone.
(iii) Dark zone.

What is the composition of a match-stick?

1

(a)

A mixture of antimony trisulphide, potassium chlorate and white phosphorous with some glue and starch applied on the head of the match stick.