Combustion Processes and Conditions

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Questions and Answers

What material is primarily used to make the wick of a candle?

Glass

Plastic

Cotton (correct)

Metal

Which zone of the candle flame is characterized by the complete combustion of wax vapours?

Non-luminous Zone (correct)

Dark Zone

Blue Zone

Luminous Zone

What causes the luminous zone of a candle flame to emit light?

Inadequate heat from the wick

Complete combustion of carbon dioxide

Incompletely burned soot particles (correct)

Rapid evaporation of the wax

What observation can be made when a glass slide is held in the luminous zone of a candle flame?

A circular grey ring forms with a center clear of deposits (B) Signup and view all the answers

What occurs in the dark zone of a candle flame?

No combustion takes place (B) Signup and view all the answers

During the combustion of the wax, what byproduct is primarily formed?

Carbon dioxide (D) Signup and view all the answers

What is the color of the luminous zone in a candle flame?

Yellow or light orange (C) Signup and view all the answers

Which statement about wax vapour in a candle is accurate?

It requires oxygen to combust (A) Signup and view all the answers

What is the primary characteristic that fuels should have to minimize environmental impact?

Burn at a slow rate (C) Signup and view all the answers

Which harmful gas produced from burning fossil fuels is lethal when inhaled in excess?

Carbon monoxide (D) Signup and view all the answers

What is formed when oxides of sulphur and nitrogen dissolve in rainwater?

Acid rain (D) Signup and view all the answers

Which of the following is a potential consequence of excess carbon dioxide in the atmosphere?

Global warming (C) Signup and view all the answers

What type of combustion occurs without any external ignition source?

Spontaneous combustion (B) Signup and view all the answers

Which type of fire extinguisher would be unsuitable for electrical fire?

Water extinguisher (A) Signup and view all the answers

What constitutes a significant health risk from suspended particulate matter (SPM)?

Asthma and bronchitis (C) Signup and view all the answers

What happens when the combustion of fuels is incomplete?

Production of suspended particulate matter (C) Signup and view all the answers

What is the primary reason that the blue zone of a flame appears blue?

Due to incomplete combustion of carbon monoxide (D) Signup and view all the answers

Which fuel is classified as a fossil fuel?

Coal (C) Signup and view all the answers

What is the ignition temperature?

The minimum temperature required for a fuel to catch fire (B) Signup and view all the answers

What characteristic is NOT desirable in a good fuel?

High cost (C) Signup and view all the answers

How does the calorific value of fuel relate to its efficiency?

Higher calorific value indicates higher efficiency (B) Signup and view all the answers

Which type of chulha utilizes only 3-10% of fuel effectively?

Traditional Chulha (C) Signup and view all the answers

What ensures the efficiency of a smokeless chulha?

Presence of a tall chimney (A) Signup and view all the answers

Which of the following is a benefit of burning fossil fuels?

They produce large amounts of energy on burning (D) Signup and view all the answers

What is the term for materials that catch fire easily in the presence of oxygen?

Flammable materials (B) Signup and view all the answers

Which of the following is NOT a condition necessary for combustion?

Existence of a catalyst (C) Signup and view all the answers

What happens when a candle is covered with a glass jar?

It stops burning (D) Signup and view all the answers

Which type of combustion occurs at low temperature and very slowly?

Slow combustion (C) Signup and view all the answers

During combustion, substances combine with which element from the air?

Oxygen (D) Signup and view all the answers

What is the primary product of slow combustion in biological processes like respiration?

Carbon dioxide and water (A) Signup and view all the answers

Why do smaller pieces of wood catch fire more easily than larger pieces?

They have a larger surface area to volume ratio (B) Signup and view all the answers

What process is described as the burning of substances resulting in the release of heat and light?

Combustion (B) Signup and view all the answers

What is the primary characteristic of rapid combustion?

It produces large amounts of heat and light. (A) Signup and view all the answers

Which example correctly illustrates spontaneous combustion?

Sodium bursting in air. (A) Signup and view all the answers

What defines an explosion in the context of combustion?

A mixture burns rapidly in a closed space. (A) Signup and view all the answers

Which of the following describes complete combustion?

Carbon dioxide is the primary product. (B) Signup and view all the answers

What is a major disadvantage of incomplete combustion?

It leads to atmospheric pollution. (C) Signup and view all the answers

What is slow combustion exemplified by in the provided content?

Formation of rust on iron. (A) Signup and view all the answers

Why is it important to have fire extinguishers readily available?

To prevent fires from spreading uncontrollably. (A) Signup and view all the answers

What key factor is required for complete combustion to take place?

Sufficient amounts of oxygen. (A) Signup and view all the answers

What are the three conditions for extinguishing fire?

Removal of combustible substance, cut off air supply, cool below ignition temperature (B) Signup and view all the answers

How does a soda-acid fire extinguisher function?

It releases carbon dioxide gas that cuts off the air supply (C) Signup and view all the answers

Which type of fire extinguisher is effective for electrical fires?

Carbon dioxide fire extinguisher (C) Signup and view all the answers

What substance is the primary component in a soda-acid fire extinguisher?

Sodium bicarbonate (B) Signup and view all the answers

In what year did Michael Faraday give his series of lectures on the chemical history of a candle flame?

1860 (A) Signup and view all the answers

What happens chemically when sodium bicarbonate reacts with sulfuric acid in a soda-acid fire extinguisher?

It produces sodium sulfate, water, and carbon dioxide (C) Signup and view all the answers

Which type of fire extinguisher is used primarily for fires caused by solid or liquid substances?

Foam type fire extinguisher (A) Signup and view all the answers

What is a common misconception about flames and burning substances?

All burning substances produce a flame (B) Signup and view all the answers

Study Notes

Combustion

Combustion is the process of burning substances in the presence of oxygen, producing heat and light.
Combustible materials catch fire easily in the presence of oxygen. Examples include paper, wood, and petrol.
Non-combustible materials do not burn easily. Examples include iron and glass.
The air or oxygen that helps in burning is called a supporter of combustion.
A chemical reaction with energy release is called combustion.

Conditions for Combustion

Three conditions are necessary for combustion:
- Presence of a combustible substance
- A supporter of combustion (like oxygen)
- Attainment of ignition temperature (the temperature at which a substance starts burning)

Types of Combustion

Slow combustion: Burning at low temperatures. Examples include respiration, digestion, and rusting.
Rapid combustion: Fast burning, producing significant heat and light. Examples include burning of matchsticks and LPG.
Spontaneous combustion: Material catching fire without an external ignition source. Example is sodium in air.

Complete and Incomplete Combustion

Complete combustion: A substance burns completely in the presence of sufficient oxygen, producing carbon dioxide and heat.
Incomplete combustion: Occurs when oxygen is limited. This produces carbon monoxide (a poisonous gas) and soot.

Activity 1

Aim: Demonstrating the process of combustion.
Materials: Magnesium ribbon, charcoal, matchstick head, tongs, and a spirit lamp.
Procedure: Separate items are heated by tongs on a spirit lamp flame.

Activity 2

Aim: Proving smaller wood pieces catch fire more easily.
Materials: Wood, splinters of wood, tongs, and a spirit lamp.
Procedure: A smaller splinter is observed to catch fire easier than a larger piece.

Activity 3

Aim: Studying spontaneous and slow combustion.
Materials: Small piece of yellow phosphorus, china dish, and rusted iron nail.
Procedure: Observe the spontaneous combustion of yellow phosphorus and the slow combustion of the rusted iron nail.

Fire Extinguishers

Devices used to put out fire.
Different types exist: soda-acid, carbon dioxide, foam, and dry powder.
Soda-acid extinguishers contain sodium bicarbonate and concentrated sulfuric acid, producing carbon dioxide to extinguish.

Flame

The flame has zones:
- Luminous zone: Visible light-emitting part, incomplete combustion.
- Dark zone: Innermost part with no combustion.
- Non-luminous zone: Outermost part, complete combustion.
- Blue zone: Carbon Monoxide produced from incomplete combustion.

Fuels

Fuels are substances that burn to produce heat.
Classification: Solid, liquid, or gaseous.
Calorific value: Amount of heat energy released when burning one gram of fuel.
- Coal, wood, and cow dung cakes are solid fuels.
- Diesel, petrol, and kerosene are liquid fuels.
- CNG, LPG, and biogas are gaseous fuels.

Ignition Temperature

The minimum temperature at which a substance ignites (starts burning).
Substances with lower ignition temperatures are more flammable.

Impacts of Burning Fuels

Burning fuels releases harmful gases like carbon dioxide, carbon monoxide, sulfur dioxide, and nitrogen oxides.
Incomplete combustion produces soot and other pollutants.
Burning fossil fuels contributes to global warming.
Burning fuels produces smoke and ash, which pollute the air.

Explosions

Occur when a mixture of combustible material and air explodes in a short time.
Examples include firecrackers and bombs.

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Description

Explore the fundamental concepts of combustion, including its definitions, types, and conditions necessary for combustion to occur. This quiz covers both combustible and non-combustible materials, along with examples of slow and rapid combustion. Test your understanding of this essential chemical reaction!