Class 8 Practice – Level 3 – Set 2 – Combustion and Flame

Total questions: 15

Why is kerosene stored in airtight containers and not left exposed to air?

To prevent spontaneous combustion

To keep its ignition temperature low

To avoid contamination from air

To maintain its calorific value

None

Which of the following changes would result in a more efficient fuel combustion process in a stove?

Reducing the airflow to the burner

Increasing the fuel supply without increasing airflow

Adjusting the burner for a blue flame

Using a fuel with a lower calorific value

None

In which of the following situations would using water to extinguish a fire be dangerous and ineffective?

A wood fire

An oil spill fire

A paper fire

A fire involving dry grass

None

Which of the following statements best explains the yellow color of a candle flame?

Complete combustion of wax molecules

Presence of excess oxygen

Incomplete combustion producing glowing carbon particles

Low temperature of the flame

None

Why is it difficult to start a fire in a damp environment, even with combustible materials?

Combustion occurs only in dry materials

Damp materials lower the ignition temperature of fuels

Water in damp materials absorbs heat, preventing ignition

Dampness raises the calorific value of materials

None

Which of the following is an example of rapid combustion?

Lighting a matchstick

Burning of phosphorus in air

Rusting of iron

Spontaneous combustion of coal

None

Which of the following safety measures should be followed to prevent fires in LPG-based kitchens?

Always leave the stove burner on low when not in use

Check for gas leaks using a flame

Turn off the gas regulator when not in use

Store LPG cylinders near heating appliances

None

Which of the following is a major hazard associated with incomplete combustion of fuels?

Release of oxygen

Emission of carbon dioxide

Formation of carbon monoxide

Decrease in energy output

None

Why is the blue flame in a gas stove considered hotter than the yellow flame of a candle?

It burns more fuel

It uses more oxygen, leading to complete combustion

It is produced by higher calorific value fuels

It contains more unburnt carbon

None

10.

Why is it dangerous to store large quantities of ammonium nitrate in an area prone to high temperatures?

It reacts with water to produce toxic fumes

It decomposes at high temperatures, releasing heat and causing an explosion

It rapidly absorbs moisture from the air

It reacts with oxygen in the air to produce flammable gases

None

11.

Which of the following pollutants is most commonly produced by the burning of fossil fuels and is responsible for respiratory problems in humans?

Ozone

Carbon dioxide

Sulfur dioxide

Nitrogen

None

12.

Why are renewable fuels like biogas considered more environmentally friendly than non-renewable fuels like coal?

Biogas produces no carbon dioxide

Biogas has a higher calorific value

Biogas combustion releases less greenhouse gases

Biogas is made from fossil fuels

None

13.

If the oxygen supply to a fire is reduced, which of the following outcomes is likely?

The fire will burn more brightly

The fire will start to produce more soot

The fire will increase in temperature

The fire will produce more blue flames

None

14.

Which zone of a candle flame is responsible for producing most of the light, and why?

The innermost zone, because it contains unburnt wax

The middle zone, because it contains partially burnt carbon particles

The outermost zone, because it is the hottest part of the flame

The blue zone, because it burns completely without producing soot

None

15.

Which of the following best explains why hydrogen is considered both a promising future fuel and a safety hazard?

It has a low ignition temperature and is non-polluting

It is highly explosive and difficult to store safely

It produces no greenhouse gases but requires expensive technology

It is abundant but reacts slowly with oxygen

None

1 out of 15

Class 8 Practice – Level 3 – Set 2 – Combustion and Flame

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