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Important Questions: Combustion And Flame - Class 8 MCQ


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20 Questions MCQ Test Science Class 8 - Important Questions: Combustion And Flame

Important Questions: Combustion And Flame for Class 8 2024 is part of Science Class 8 preparation. The Important Questions: Combustion And Flame questions and answers have been prepared according to the Class 8 exam syllabus.The Important Questions: Combustion And Flame MCQs are made for Class 8 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Important Questions: Combustion And Flame below.
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Important Questions: Combustion And Flame - Question 1

Burning of charcoal in a closed room will produce

Detailed Solution for Important Questions: Combustion And Flame - Question 1
Incomplete combustion of coal gives carbon monoxide gas. It is a very poisonous gas. It is dangerous to burn coal in a closed room. The carbon monoxide gas produced can kill persons sleeping in that room. So we should not sleep in a closed room with burning coal fire in it.
Important Questions: Combustion And Flame - Question 2

What is the role of baking soda in a homemade fire extinguisher model?

Detailed Solution for Important Questions: Combustion And Flame - Question 2
Baking soda releases carbon dioxide when it reacts with vinegar, helping to extinguish flames by displacing oxygen and lowering the temperature around the fire.
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Important Questions: Combustion And Flame - Question 3

Which of the following is a zone of a flame?

I. Dark

II. Luminous

III. Non-Luminous

Detailed Solution for Important Questions: Combustion And Flame - Question 3

- Dark, Luminous, and Non-Luminous are the three zones of a flame.
- Dark Zone: The innermost zone where combustion is incomplete due to lack of oxygen.
- Luminous Zone: The middle zone where combustion is complete, emitting light and heat.
- Non-Luminous Zone: The outermost zone where combustion is also complete but lacks sufficient heat to emit light.
- Therefore, the correct answer is B: I, II, and III.

Important Questions: Combustion And Flame - Question 4
What type of reaction occurs when a cracker explodes?
Detailed Solution for Important Questions: Combustion And Flame - Question 4
An explosion is a type of combustion reaction that occurs very rapidly, releasing a large amount of energy in the form of heat, light, and sound, along with gas expansion.
Important Questions: Combustion And Flame - Question 5

Which zone of a candle flame is the hottest?

Detailed Solution for Important Questions: Combustion And Flame - Question 5

- The outer zone of a candle flame is the hottest part.
- This zone has a blue hue due to complete combustion.
- Oxygen is plentiful here, allowing the fuel to burn efficiently.
- The temperature in the outer zone can reach up to 1400°C.
- In contrast, the inner zone is cooler because it lacks sufficient oxygen, resulting in incomplete combustion.
- The outer zone's efficiency and high temperature make it the hottest part of the flame.

Important Questions: Combustion And Flame - Question 6

The innermost part of the flame has very least temperature.

Detailed Solution for Important Questions: Combustion And Flame - Question 6

Explanation:
- The innermost part of a flame, known as the blue part or the core, actually has the least temperature compared to the outer parts of the flame.
- This might seem counterintuitive since we usually associate blue flames with high heat, but in reality, the outer parts of the flame are hotter as they contain more oxygen and burn more efficiently.
- Understanding this concept helps in applications like cooking and welding where different parts of the flame are used for specific purposes.

Important Questions: Combustion And Flame - Question 7
What type of combustion occurs when a material suddenly bursts into flames without an apparent cause?
Detailed Solution for Important Questions: Combustion And Flame - Question 7
Spontaneous combustion occurs when a material ignites without an apparent external source of ignition, often due to chemical reactions or heat accumulation within the material.
Important Questions: Combustion And Flame - Question 8
Which of the following is an inflammable substance?
Detailed Solution for Important Questions: Combustion And Flame - Question 8
Petrol is an inflammable substance with a low ignition temperature, meaning it can easily catch fire when exposed to a flame or spark.
Important Questions: Combustion And Flame - Question 9

Oxygen is required for the burning of any substance.

Detailed Solution for Important Questions: Combustion And Flame - Question 9

The statement that oxygen is required for the burning of any substance is true. Oxygen acts as an oxidizing agent, allowing substances to undergo combustion and release energy in the form of heat and light.

Important Questions: Combustion And Flame - Question 10
Which substance is not suitable for extinguishing oil fires?
Detailed Solution for Important Questions: Combustion And Flame - Question 10
- Water is not suitable for extinguishing oil fires because it is denser than oil.
- When water is poured on burning oil, it sinks beneath the oil and can vaporize rapidly, creating steam.
- This steam can expand and force the burning oil to spread, worsening the fire.
- Using alternatives like carbon dioxide, dry powder, or foam is safer as they effectively smother the flames without causing the fire to spread.
Important Questions: Combustion And Flame - Question 11
What is produced along with heat during the process of combustion?
Detailed Solution for Important Questions: Combustion And Flame - Question 11
During combustion, light is often produced along with heat, as seen in flames and other burning processes where energy is released in the form of light.
Important Questions: Combustion And Flame - Question 12
Which gas is commonly used in fire extinguishers for electrical fires?
Detailed Solution for Important Questions: Combustion And Flame - Question 12
Carbon dioxide is commonly used in fire extinguishers for electrical fires because it is non-conductive and helps smother the fire by displacing oxygen, thereby preventing combustion.
Important Questions: Combustion And Flame - Question 13
What is the main component of a safety match head?
Detailed Solution for Important Questions: Combustion And Flame - Question 13
The head of a safety match primarily contains antimony trisulphide, which ignites when struck against the matchbox, starting the combustion process.
Important Questions: Combustion And Flame - Question 14

The substances which have very low ignition temperature will

Detailed Solution for Important Questions: Combustion And Flame - Question 14

The substances which have very low ignition temperature and can easily catch fire with a flame are called inflammable substances. Examples of inflammable substances are petrol, alcohol, Liquified Petroleum Gas (LPG) etc.

Important Questions: Combustion And Flame - Question 15
Which fuel has the highest calorific value?
Detailed Solution for Important Questions: Combustion And Flame - Question 15
Hydrogen has the highest calorific value among common fuels, producing the most energy per unit mass when combusted.
Important Questions: Combustion And Flame - Question 16

Ignition temperature is

Detailed Solution for Important Questions: Combustion And Flame - Question 16

The ignition temperature refers to the minimum temperature at which a substance or material can ignite and sustain combustion. It is an important parameter to understand the fire hazards associated with different substances.
Answer: A - The lowest temperature to catch fire.

Important Questions: Combustion And Flame - Question 17

Coal burns with

Detailed Solution for Important Questions: Combustion And Flame - Question 17

Coal is a natural fossil fuel that can burn with both a flame and glow. The flame is produced due to the volatile matter present in coal, which vaporizes and ignites, while the glow is due to the combustion of the solid carbon content. Therefore, coal can exhibit both flame and glow when it burns.

Important Questions: Combustion And Flame - Question 18
Which substance is a cleaner fuel compared to diesel and petrol?
Detailed Solution for Important Questions: Combustion And Flame - Question 18
Compressed Natural Gas (CNG) is considered a cleaner fuel compared to diesel and petrol because it produces fewer harmful emissions and pollutants when burned.
Important Questions: Combustion And Flame - Question 19

The substances which give heat and light after combustion are called _________________.

Detailed Solution for Important Questions: Combustion And Flame - Question 19
  • The substance which undergoes combustion is said to be combustible. It is called fuel.
  • If a magnesium ribbon is heated,it starts burning.
  • When a magnesium ribbon burns, it combines with the oxygen of air to form magnesium oxide, and liberates heat and light.
Important Questions: Combustion And Flame - Question 20

The products of combustion are

Detailed Solution for Important Questions: Combustion And Flame - Question 20

Products of combustion depend upon the nature of the combustible substance. Most of the fuel that we use are hydrocarbons.

Compounds of hydrogen and carbon are called hydrocarbons.

For e.g. LPG (main constituent is butane or C4H10), natural gas (methane or CH4), petrol etc.

When such fuels burn, the main products are carbon dioxide and water. 

For e.g. Methane + oxygen Combustion and flame Carbon dioxide + Water.

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