Combustion and Flame Class 8 MCQ: Understanding the Science of Fire

Welcome, young explorers of science! Today, we embark on an exhilarating journey into the fascinating world of combustion and flame. Join us as we delve into the realm of fire and discover the secrets behind this mystical phenomenon that has intrigued humanity for ages. In our Class 8 MCQ (Multiple Choice Questions) adventure, we will unravel the mysteries of combustion, the process that ignites everything from a tiny matchstick to roaring forest fires. We will also explore the mesmerizing dance of flames, understanding the chemistry behind their captivating colors and the science that keeps them alive.

As we progress through this interactive learning experience, you will have the opportunity to test your knowledge, challenge your understanding, and have fun with an array of thought-provoking MCQs. From the basics of combustion to the different types of flames and their significance, we will cover it all!

But wait, that's not all! Along the way, we'll be uncovering some real-life applications of combustion and exploring how this natural phenomenon has shaped human civilization throughout history. From early discoveries like the invention of fire to modern-day applications that power our industries, you'll witness the incredible impact combustion has on our daily lives.

So, gear up for an unforgettable journey of discovery, where science meets excitement, and curiosity fuels the flames of learning. Get ready to test your knowledge, ignite your passion for science, and let your understanding burn brighter than ever before!

Are you ready to immerse yourself in the captivating world of combustion and flame? Then let's ignite the spark of knowledge and embark on this extraordinary adventure together! Remember, the more you learn, the brighter you'll shine!

Let's begin our Class 8 MCQ exploration of combustion and flame!

50 multiple-choice questions with answers and explanations on the topic of Combustion and Flame for Class 8:

1. What is combustion?

   a) The process of converting solid to liquid

   b) The process of converting liquid to gas

   c) The process of burning of a substance in the presence of oxygen

   d) The process of freezing a substance

   

Answer: c) The process of burning of a substance in the presence of oxygen

   Explanation: Combustion is a chemical process in which a substance reacts with oxygen, producing heat and light.

2. Which of the following is a product of complete combustion?

   a) Carbon monoxide (CO)

   b) Carbon dioxide (CO2)

   c) Methane (CH4)

   d) Sulfur dioxide (SO2)

   Answer: b) Carbon dioxide (CO2)

   Explanation: In complete combustion, the fuel burns completely, producing carbon dioxide and water as the main products.

3. A glowing splinter burns vigorously when brought near a gas. The gas is most likely to be:

   a) Oxygen

   b) Hydrogen

   c) Nitrogen

   d) Carbon dioxide

   Answer: a) Oxygen

   Explanation: Oxygen supports combustion, and when a glowing splinter is brought near it, it ignites and burns vigorously.

4. Which of the following is an example of rapid combustion?

   a) Rusting of iron

   b) Digestion of food

   c) Burning of paper

   d) Ripening of fruits

   Answer: c) Burning of paper

   Explanation: Rapid combustion is a fast and uncontrolled type of combustion. Burning of paper is an example of rapid combustion.

5. A safety feature in electrical appliances that prevents fires due to overheating is called:

   a) Insulation

   b) Combustion

   c) Circuit breaker

   d) Conduction

   Answer: c) Circuit breaker

   Explanation: Circuit breakers are safety devices that automatically switch off the electrical circuit when there is excessive current or overheating, preventing fires.

6. The minimum temperature at which a substance catches fire and starts to burn is called:

   a) Ignition temperature

   b) Boiling point

   c) Melting point

   d) Flashpoint

   Answer: a) Ignition temperature

   Explanation: Ignition temperature is the minimum temperature required for a substance to catch fire and start burning.

7. A candle flame primarily consists of:

   a) Carbon dioxide and nitrogen

   b) Oxygen and water vapor

   c) Methane and carbon dioxide

   d) Wax vapors and nitrogen

   Answer: b) Oxygen and water vapor

   Explanation: The burning of a candle produces a flame primarily composed of oxygen and water vapor along with some unburnt carbon particles that make the flame visible.

8. The outermost zone of a candle flame is:

   a) The dark zone

   b) The non-luminous zone

   c) The luminous zone

   d) The blue zone

   Answer: b) The non-luminous zone

   Explanation: The outermost zone of a candle flame is the non-luminous zone, which is pale blue and has the least amount of heat.

9. Which gas is released when a metal burns in air?

   a) Carbon dioxide

   b) Oxygen

   c) Hydrogen

   d) Nitrogen dioxide

   Answer: a) Carbon dioxide

   Explanation: When a metal burns in air, it combines with oxygen to form metal oxides, and carbon dioxide is released.

10. The process of producing biogas is an example of:

    a) Combustion

    b) Slow combustion

    c) Spontaneous combustion

    d) None of the above

    Answer: b) Slow combustion

    Explanation: Biogas production involves slow combustion of organic matter in the absence of oxygen.

11. Which of the following is a fossil fuel?

    a) Biogas

    b) Natural gas

    c) Hydrogen gas

    d) Compressed air

    Answer: b) Natural gas

    Explanation: Natural gas is a fossil fuel formed from the remains of plants and animals over millions of years.

12. The presence of which gas in the atmosphere is mainly responsible for the greenhouse effect?

    a) Oxygen

    b) Nitrogen

    c) Carbon dioxide

    d) Hydrogen

    Answer: c) Carbon dioxide

    Explanation: Carbon dioxide is a greenhouse gas that traps heat in the Earth's atmosphere, contributing to the greenhouse effect and global warming.

13. What is the color of the innermost zone of a candle flame?

    a) Blue

    b) Red

    c) Yellow

    d) Black

    Answer: c) Yellow

    Explanation: The innermost zone of a candle flame is yellow in color and is the hottest part of the flame.

14. In a fire extinguisher, the substance that puts out the fire by cutting off the supply of oxygen is:

    a) Carbon dioxide

    b) Water

    c) Sand

    d) Nitrogen

    Answer: a) Carbon dioxide

    Explanation: Carbon dioxide fire extinguishers work by displacing oxygen, which cuts off the supply of oxygen to the fire and extinguishes it.

15. Which type of flame is produced by burning of a paper?

    a) Non-luminous flame

    b) Luminous flame

    c) Blue flame

    d) Red flame

    Answer: b) Luminous flame

    Explanation: When paper burns, it produces a luminous flame due to the presence of unburnt carbon particles, which glow and emit light.

16. The fuel used in a car engine is an example of:

    a) Solid fuel

    b) Liquid fuel

    c) Gaseous fuel

    d) Plasma fuel

    Answer: b) Liquid fuel

    Explanation: Most car engines use liquid fuels like petrol or diesel for combustion.

17. Which of the following is NOT required for combustion to take place?

    a) Heat

    b) Oxygen

    c) Fuel

    d) Nitrogen

    Answer: d) Nitrogen

    Explanation: Nitrogen is not directly involved in the process of combustion; it makes up a significant portion of the atmosphere and does not react with the fuel.

18. Which zone of a candle flame is the hottest?

    a) The dark zone

    b) The non-luminous zone

    c) The luminous zone

    d) The blue zone

    Answer: d) The blue zone

    Explanation: The blue zone of a candle flame is the hottest and is located at the base of the flame.

19. The process in which a substance reacts with oxygen and produces heat and light is called:

    a) Evaporation

    b) Sublimation

    c) Combustion

    d) Condensation

    Answer: c) Combustion

    Explanation: Combustion is the process of burning a substance in the presence of oxygen, resulting in the release of heat and light.

20. Which of the following is an example of spontaneous combustion?

    a) Lighting a matchstick

    b) A piece of wood burning in a camp fire

    c) A haystack catching fire on its own

    d) Burning of candles

    Answer: c) A haystack catching fire on its own

    Explanation: Spontaneous combustion is a type of combustion that occurs without any external ignition source. In some cases, a haystack can catch fire due to the heat generated by microbial activity inside it.

21. The flame produced by a gas stove is an example of:

    a) Non-luminous flame

    b) Luminous flame

    c) Blue flame

    d) Red flame

    Answer: b) Luminous flame

    Explanation: The flame produced by a gas stove is a luminous flame, which appears yellow due to the presence of unburnt carbon particles.

22. What is the primary constituent of liquefied petroleum gas (LPG)?

    a) Methane

    b) Propane

    c) Ethane

    d) Butane

    Answer: b) Propane

    Explanation: LPG (liquefied petroleum gas) primarily contains propane and butane.

23. The process of photosynthesis can be considered the reverse of:

    a) Combustion

    b) Evaporation

    c) Condensation

    d) Sublimation

    Answer: a) Combustion

    Explanation: Photosynthesis is the process of converting carbon dioxide and water into glucose and oxygen, which is essentially the reverse of combustion where glucose and oxygen combine to produce carbon dioxide and water.

24. A fuel with a high ignition temperature is considered:

    a) Safer to use

    b) More likely to cause explosions

    c) More prone to spontaneous combustion

    d) None of the above

    Answer: a) Safer to use

    Explanation: A fuel with a high ignition temperature is safer to use because it requires a higher temperature to catch fire, reducing the risk of accidental ignition.

25. When burning magnesium ribbon, the ash formed is:

    a) Magnesium oxide

    b) Magnesium hydroxide

    c) Magnesium carbonate

    d) Magnesium chloride

    Answer: a) Magnesium oxide

    Explanation: Burning magnesium ribbon in air produces magnesium oxide as the ash.

26. The type of flame produced by burning methane gas is:

    a) Non-luminous flame

    b) Luminous flame

    c) Blue flame

    d) Red flame

    Answer: a) Non-luminous flame

    Explanation: Methane gas produces a non-luminous blue flame when burned completely.

27. The process of slow burning of a substance in the presence of oxygen is called:

    a) Rapid combustion

    b) Spontaneous combustion

    c) Slow combustion

    d) Sublimation

    Answer: c) Slow combustion

    Explanation: Slow combustion is a slow and controlled type of combustion that occurs when a substance burns gradually in the presence of oxygen.

28. Which of the following is an example of a natural source of fire?

    a) Candle flame

    b) Lightning

    c) Cooking gas stove

    d) Welding torch

    Answer: b) Lightning

    Explanation: Lightning is a natural source of fire caused by the discharge of electricity in the atmosphere, resulting in combustion.

29. The phenomenon of 'backdraft' in firefighting is caused by:

    a) Rapid combustion

    b) Slow combustion

    c) Spontaneous combustion

    d) Sudden influx of oxygen

    Answer: d) Sudden influx of oxygen

    Explanation: Backdraft occurs when a sudden influx of oxygen reignites smoldering materials, causing a rapid and intense combustion.

30. Which of the following is a renewable source of energy used for cooking and heating?

    a) Coal

    b) Natural gas

    c) Biogas

    d) Petrol

    Answer: c) Biogas

    Explanation: Biogas is a renewable source of energy produced from the decomposition of organic matter in the absence of oxygen.

31. The color of the outermost zone of a candle flame is:

    a) Blue

    b) Red

    c) Yellow

    d) Black

    Answer: a) Blue

    Explanation: The outermost zone of a candle flame is blue in color and has the least amount of heat.

32. Which of the following is NOT a necessary condition for combustion to occur?

    a) Presence of oxygen

    b) Ignition temperature

    c) Presence of a fuel

    d) High pressure

    Answer: d) High pressure

    Explanation: High pressure is not a necessary condition for combustion to occur. The presence of oxygen, ignition temperature, and fuel are the critical factors.

33. The energy stored in fossil fuels originally comes from:

    a) The Sun

    b) Geothermal sources

    c) Radioactive elements

    d) Wind

    Answer: a) The Sun

    Explanation: The energy stored in fossil fuels, such as coal, oil, and natural gas, originally comes from the Sun. These fuels are formed from ancient plants and animals that captured solar energy through photosynthesis.

34. Which of the following is an example of a natural fire retardant?

    a) Water

    b) Sand

    c) Oxygen

    d) Hydrogen

    Answer: b) Sand

    Explanation: Sand can be used as a fire retardant because it is an effective heat insulator, preventing the fire from spreading.

35. A substance with a low ignition temperature is considered:

    a) Safer to use

    b) More likely to cause explosions

    c) More prone to spontaneous combustion

    d) None of the above

    Answer: c) More prone to spontaneous combustion

    Explanation: A substance with a low ignition temperature is more likely to catch fire spontaneously, making it more prone to spontaneous combustion.

36. The fuel used in the wick of a candle is:

    a) Paraffin wax

    b) Methane gas

    c) Kerosene

    d) LPG

    Answer: a) Paraffin wax

    Explanation: The fuel used in the wick of a candle is paraffin wax, which is a solid hydrocarbon.

37. What is the source of energy that powers the Sun and other stars?

    a) Nuclear fission

    b) Nuclear fusion

    c) Combustion

    d) Chemical reactions

    Answer: b) Nuclear fusion

    Explanation: The Sun and other stars produce energy through nuclear fusion, where hydrogen nuclei combine to form helium, releasing an enormous amount of energy.

38. Which of the following is an example of a gaseous fuel?

    a) Coal

    b) Wood

    c) Diesel

    d) Hydrogen

    Answer: d) Hydrogen

    Explanation: Hydrogen is an example of a gaseous fuel.

39. The process of burning magnesium in air is an example of:

    a) Rapid combustion

    b) Slow combustion

    c) Spontaneous combustion

    d) None of the above

    Answer: a) Rapid combustion

    Explanation: Burning magnesium in air is an example of rapid combustion.

40. Which of the following is a safety measure to prevent fires in homes?

    a) Leaving electrical appliances plugged in

    b) Using frayed electrical cords

    c) Storing flammable liquids near a heat source

    d) Installing smoke detectors

    Answer: d) Installing smoke detectors

    Explanation: Installing smoke detectors is a safety measure to detect smoke early and alert occupants of a potential fire.

41. Which gas is released when a fossil fuel is burned in a limited supply of air?

    a) Carbon dioxide

    b) Carbon monoxide

    c) Nitrogen

    d) Oxygen

    Answer: b) Carbon monoxide

    Explanation: When a fossil fuel is burned in a limited supply of air, it produces carbon monoxide, a toxic and harmful gas.

42. The chemical formula for methane gas is:

    a) CH3OH

    b) CO2

    c) CH4

    d) C2H6

    Answer: c) CH4

    Explanation: The chemical formula for methane gas is CH4.

43. Which of the following is a by-product of the combustion of fossil fuels?

    a) Oxygen

    b) Nitrogen

    c) Carbon dioxide

    d) Hydrogen

    Answer: c) Carbon dioxide

    Explanation: The combustion of fossil fuels produces carbon dioxide as a by-product.

44. The flame produced by burning a candle is:

    a) Non-luminous

    b) Luminous

    c) Blue

    d) Red

    Answer: b) Luminous

    Explanation: The flame produced by burning a candle is luminous due to the presence of unburnt carbon particles, which emit light and make the flame visible.

45. In a fire triangle, what are the three components required for combustion?

    a) Heat, oxygen, and fuel

    b) Water, oxygen, and fuel

    c) Heat, nitrogen, and fuel

    d) Heat, carbon dioxide, and fuel

    Answer: a) Heat, oxygen, and fuel

    Explanation: The fire triangle represents the three components necessary for combustion: heat, oxygen, and fuel.

46. Which of the following is an example of a renewable source of energy?

    a) Natural gas

    b) Coal

    c) Solar energy

    d) Diesel

    Answer: c) Solar energy

    Explanation: Solar energy is a renewable source of energy that comes from the Sun and is harnessed using solar panels.

47. The process of converting a solid directly into a gas without passing through the liquid state is called:

    a) Combustion

    b) Evaporation

    c) Sublimation

    d) Condensation

    Answer: c) Sublimation

    Explanation: Sublimation is the process of converting a solid directly into a gas without going through the liquid phase.

48. The phenomenon of 'backdraft' in firefighting is caused by:

    a) Rapid combustion

    b) Slow combustion

    c) Spontaneous combustion

    d) Sudden influx of oxygen

    Answer: d) Sudden influx of oxygen

    Explanation: Backdraft occurs when a sudden influx of oxygen reignites smoldering materials, causing a rapid and intense combustion.

49. Which of the following is NOT a necessary condition for combustion to occur?

    a) Presence of oxygen

    b) Ignition temperature

    c) Presence of a fuel

    d) High pressure

    Answer: d) High pressure

    Explanation: High pressure is not a necessary condition for combustion to occur. The presence of oxygen, ignition temperature, and fuel are the critical factors.

50. The energy stored in fossil fuels originally comes from:

    a) The Sun

    b) Geothermal sources

    c) Radioactive elements

    d) Wind

    Answer: a) The Sun

    Explanation: The energy stored in fossil fuels, such as coal, oil, and natural gas, originally comes from the Sun. These fuels are formed from ancient plants and animals that captured solar energy through photosynthesis.