Questions and Answers
What happens to the flame when a glass plate is placed over the chimney, as described in the text?
The flame flickers off due to lack of air.
What can be inferred about the role played by air in the process of burning, based on the text?
Air is essential for combustion.
Why does a piece of wood or coal require paper or kerosene oil to start burning, according to the text?
To provide an initial source of ignition.
What happens when a burning matchstick is brought near a piece of wood, as discussed in the text?
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Is the sun's heat and light production considered a form of combustion, according to the text?
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Why does a candle burn freely in a chimney when air can enter from below, as mentioned in the text?
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What type of fuel vapourises during burning and gives flames?
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Why does charcoal not produce a flame when burned?
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What causes the deposition of unburnt carbon particles on the glass plate/slide?
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In the non-luminous zone of the flame, what part is considered to be the hottest?
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What is the circular blackish ring on the glass plate/slide a sign of?
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Why does the portion of the copper wire just outside the flame get red hot?
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What are the characteristics of a good fuel?
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Why is there probably no ideal fuel?
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Why does a goldsmith use the outermost zone of a flame?
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What are the three zones of a candle flame?
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Why should a fuel not leave behind any undesirable substances?
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If you were asked to choose a fuel to boil water among cow dung, coal, and LPG, which would you prefer?
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Study Notes
Flame Behavior and Air's Role
- Placing a glass plate over a chimney extinguishes the flame due to restricted air supply.
- Air is essential for combustion; a lack of air stops burning processes.
Starting Combustion
- Wood or coal requires paper or kerosene oil to ignite due to their higher ignition temperatures.
- A burning matchstick can ignite wood by providing the necessary initial heat.
Combustion and Sunlight
- The sun's heat and light are not classified as combustion, as they do not involve a chemical reaction with oxygen.
Candle Flame Dynamics
- A candle burns freely in a chimney because it allows air to flow in from below, supporting combustion.
- Fuel that vaporizes during combustion produces flames, while solids generally do not.
Characteristics of Charcoal and Deposits
- Charcoal does not produce a flame when burned; it mainly converts to heat without generating volatile gases.
- Unburnt carbon particles are deposited on the glass plate due to incomplete combustion, reflecting inefficient burning.
Candle Flame Zones
- The hottest part of a flame is found in the non-luminous zone, where combustion is more efficient.
- The circular blackish ring on the glass plate indicates areas of incomplete combustion.
Heat Transmission and Fuel Properties
- A copper wire outside the flame becomes red hot due to heat conduction from the flame’s high temperatures.
- Good fuels possess characteristics such as high energy content, clean burning, and availability.
- There is likely no ideal fuel due to varying efficiencies, availability, and environmental impacts.
Goldsmithing and Fuel Choices
- Goldsmiths utilize the outermost zone of flames for detailed work, where temperatures are hotter and more controllable.
- A fuel should not leave behind undesirable substances, as this can lead to pollution and maintenance issues.
Fuel Selection
- Among cow dung, coal, and LPG, LPG is preferable for boiling water due to its clean burning and high energy efficiency.
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Description
Test your knowledge on the different zones of a candle flame and the characteristics of good fuels. Learn about the outermost zone of complete combustion (blue), moderately hot middle zone of partial combustion (yellow), and the least hot innermost zone of unburnt wax vapors (black). Explore the properties of fuels that make them effective for burning.
