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Class 8 Science Chapter 4 Combustion and Flame

This quiz on Combustion and Flame is designed to assess students' understanding of the process of burning, types of combustion, and characteristics of flames. It covers key topics such as conditions necessary for combustion, types of fuels, fire control measures, calorific value, fuel efficiency, and the harmful effects of burning fuels. Through multiple-choice and short-answer questions, students will test their knowledge while receiving instant feedback and explanations for incorrect answers. The quiz also includes supplementary notes and video links for better clarity. If you score 50% or above, you will receive a Certificate of Achievement by mail. All the best! Take the quiz and identify your weaker topics and subtopics.

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Category: Introduction to Combustion and Flame

1. Why does a candle burn with a flame while coal does not?

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Category: Introduction to Combustion and Flame

2. (A) Combustion is a chemical process that always produces a flame.
(R) A flame is produced when a substance undergoes combustion and releases light and heat.

3 / 100

Category: Definition of combustion

3. Which of the following statements best describes the nature of a fuel in a combustion reaction?

4 / 100

Category: Definition of combustion

4. What is the process called when a substance reacts with oxygen to give off heat?

5 / 100

Category: Examples of different fuels used at home, in industries, and for automobiles

5. Which of the following is a gaseous fuel commonly used in automobiles?

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Category: Examples of different fuels used at home, in industries, and for automobiles

6. (A) Compressed Natural Gas (CNG) is considered a better fuel than petrol for automobiles because it produces less harmful emissions.
(R) CNG burns more efficiently and completely than petrol, resulting in lower levels of carbon monoxide and hydrocarbons.

7 / 100

Category: Difference between burning of a candle and burning of a fuel like coal

7. Which of the following fuels is commonly used for running automobiles?

8 / 100

Category: Difference between burning of a candle and burning of a fuel like coal

8. Consider the combustion of a candle and coal. Which of the following statements correctly describes the difference in their combustion processes?

9 / 100

Category: Chemical process of burning and types of flames

9. Which of the following fuels is commonly used in homes?

10 / 100

Category: Chemical process of burning and types of flames

10. What does the presence of a blackish ring on a glass plate indicate when introduced into the luminous zone of a candle flame?

11 / 100

Category: What is Combustion?

11. Which of the following substances is considered combustible and can undergo combustion in the presence of oxygen?

12 / 100

Category: What is Combustion?

12. Which of the following statements correctly defines a combustible substance?

13 / 100

Category: Definition: A chemical process in which a substance reacts with oxygen to give off heat

13. What are the main products of combustion during the burning of magnesium ribbon?

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Category: Definition: A chemical process in which a substance reacts with oxygen to give off heat

14. A fire breaks out in an electrical equipment room. Which of the following is the most suitable extinguisher to use?

15 / 100

Category: Combustible substances: Examples (wood, kerosene, charcoal, etc.)

15. During combustion, which of the following is primarily released?

16 / 100

Category: Combustible substances: Examples (wood, kerosene, charcoal, etc.)

16. What is the main requirement for combustion to occur?

17 / 100

Category: Conditions necessary for combustion:

17. Which of the following materials would you classify as non-combustible based on their properties?

18 / 100

Category: Conditions necessary for combustion:

18. A piece of magnesium ribbon is burned in the presence of oxygen. What are the products formed during this combustion process?

19 / 100

Category: Presence of fuel

19. Consider the combustion of different types of fuels. Which type of fuel would require the highest temperature to initiate combustion under similar conditions?

20 / 100

Category: Presence of fuel

20. Which of the following substances undergoes combustion?

21 / 100

Category: Oxygen (air)

21. What is essential for combustion to occur?

22 / 100

Category: Oxygen (air)

22. Why does a candle flame go off when covered with a glass?

23 / 100

Category: Ignition temperature

23. (A) A paper cup filled with water does not burn when heated because water absorbs the heat supplied.
(R) The ignition temperature of paper is not reached due to the heat transfer to water by conduction.

24 / 100

Category: Ignition temperature

24. A paper cup filled with water is heated over a flame. Why does the paper cup not burn even though it is directly exposed to the flame?

25 / 100

Category: Concept of ignition temperature

25. Why does a matchstick not catch fire on its own at room temperature?

26 / 100

Category: Concept of ignition temperature

26. Why does a paper cup with water not burn when heated with a candle?

27 / 100

Category: Inflammable substances (e.g., petrol, alcohol, LPG)

27. Which property makes Liquified Petroleum Gas (LPG) an inflammable substance?

28 / 100

Category: Inflammable substances (e.g., petrol, alcohol, LPG)

28. Which of the following is an example of an inflammable substance?

29 / 100

Category: How Do We Control Fire?

29. Why is water not suitable for extinguishing oil fires?

30 / 100

Category: How Do We Control Fire?

30. Which type of fire extinguisher is most suitable for electrical fires?

31 / 100

Category: Fire brigade and its role

31. (A) Water is the most suitable fire extinguisher for all types of fires.
(R) Water cools the combustible material and cuts off the supply of air, making it effective for all fires.

32 / 100

Category: Fire brigade and its role

32. In the event of a fire in a residential area, what should be the first action taken by residents after ensuring their safety?

33 / 100

Category: Role of water in extinguishing fire:

33. (A) Water is used to extinguish fires because it cools the combustible material below its ignition temperature.
(R) Cooling the material reduces the temperature, preventing the fire from spreading.

34 / 100

Category: Role of water in extinguishing fire:

34. Why does water help in extinguishing a fire?

35 / 100

Category: Cools combustible material below ignition temperature

35. What is the primary role of water in extinguishing a fire?

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Category: Cools combustible material below ignition temperature

36. When water is poured on a fire, it not only cools the combustible material but also produces water vapour. What is the primary role of water vapour in extinguishing the fire?

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Category: Water vapor cuts off oxygen supply

37. Why does pouring water on a fire help in extinguishing it?

38 / 100

Category: Water vapor cuts off oxygen supply

38. What is the primary function of a fire extinguisher?

39 / 100

Category: Limitations of water as a fire extinguisher:

39. Why is water not suitable for extinguishing oil fires?

40 / 100

Category: Limitations of water as a fire extinguisher:

40. How does the release of dry powder chemicals like sodium bicarbonate help in extinguishing fires?

41 / 100

Category: Not suitable for electrical fires

41. What makes carbon dioxide ($CO_2$) an effective fire extinguisher for electrical fires?

42 / 100

Category: Not suitable for electrical fires

42. What happens when carbon dioxide ($CO_2$) is released from a high-pressure cylinder to extinguish a fire?

43 / 100

Category: Not effective for oil or petrol fires

43. Why water is not suitable for extinguishing oil or petrol fires?

44 / 100

Category: Not effective for oil or petrol fires

44. What happens when sodium bicarbonate (baking soda) is used near a fire?

45 / 100

Category: CO₂ as the best extinguisher for electrical and petrol fires

45. In what form is carbon dioxide ($CO_2$) stored in fire extinguisher cylinders?

46 / 100

Category: CO₂ as the best extinguisher for electrical and petrol fires

46. (A) Carbon dioxide is the best extinguisher for fires involving electrical equipment and inflammable materials like petrol.
(R) $CO_2$ cuts off the contact between fuel and oxygen, thus controlling the fire.

47 / 100

Category: Role of dry chemical powders like sodium bicarbonate

47. Carbon dioxide ($CO_2$) is stored in cylinders at high pressure for use in fire extinguishers. What happens when $CO_2$ is released from the cylinder during a fire?

48 / 100

Category: Role of dry chemical powders like sodium bicarbonate

48. Sodium bicarbonate ($NaHCO_3$) is used as a dry chemical powder in fire extinguishers. What chemical reaction occurs when sodium bicarbonate is exposed to heat near a fire?

49 / 100

Category: Types of Combustion

49. When a gas stove is turned on, the gas burns rapidly, producing heat and light. What type of combustion is this?

50 / 100

Category: Types of Combustion

50. (A) Spontaneous combustion occurs only in substances that are highly combustible at room temperature.
(R) Phosphorus is an example of a substance that undergoes spontaneous combustion because it reacts with oxygen in the air at room temperature.

51 / 100

Category: Rapid Combustion: Example - Gas stove burning

51. What type of combustion occurs when a gas stove is lit and burns rapidly producing heat and light?

52 / 100

Category: Rapid Combustion: Example - Gas stove burning

52. In a coal mine, coal dust suddenly ignites without any external cause, leading to a fire. At the same time, a cracker explodes during a festival, producing heat, light, and sound. Which types of combustion are being described in these two situations?

53 / 100

Category: Spontaneous Combustion: Example - Phosphorus catching fire, coal dust fires, forest fires

53. (A) Phosphorus catches fire at room temperature without any external heat source.
(R) Spontaneous combustion occurs when a material suddenly bursts into flames without any apparent cause.

54 / 100

Category: Spontaneous Combustion: Example - Phosphorus catching fire, coal dust fires, forest fires

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

55 / 100

Category: Explosion: Example - Firecrackers releasing heat, light, and sound

55. (A) When a firecracker explodes, it releases heat, light, and sound due to a rapid chemical reaction.
(R) The explosion occurs because the reaction produces a large amount of gas that is suddenly liberated.

56 / 100

Category: Explosion: Example - Firecrackers releasing heat, light, and sound

56. A firecracker explodes due to a sudden reaction that releases heat, light, and sound. If the total energy released is 5000 J, where 40% is converted to heat, 30% to light, and the rest to sound, what is the energy released as sound?

57 / 100

Category: Flame

57. What does a copper wire getting red hot just outside the non-luminous zone of a flame indicate?

58 / 100

Category: Flame

58. Which of the following materials does not produce a flame when burned?

59 / 100

Category: Observations of an LPG flame and candle flame

59. Which of the following materials does NOT produce a flame when burned?

60 / 100

Category: Observations of an LPG flame and candle flame

60. The colour of a flame can indicate the efficiency of combustion. Which of the following materials, when burned, is most likely to produce a blue flame indicating complete combustion?

61 / 100

Category: Characteristics of substances that give flames

61. (A) Charcoal does not produce a flame when burnt.
(R) Substances that vapourise during burning produce flames.

62 / 100

Category: Characteristics of substances that give flames

62. Which of the following substances does NOT produce a flame when burned?

63 / 100

Category: Structure of a Flame

63. (A) The non-luminous zone of a candle flame has the highest temperature.
(R) The non-luminous zone is where complete combustion occurs, resulting in higher temperature compared to other zones.

64 / 100

Category: Structure of a Flame

64. A candle flame is observed to have three distinct zones: the dark zone, the luminous zone, and the non-luminous zone. If a thin glass tube is introduced into the dark zone of the flame and vapours are collected, what is the primary reason for the formation of a flame at the other end of the tube?

65 / 100

Category: Three different zones of a flame:

65. Which zone of the flame has the highest temperature?

66 / 100

Category: Three different zones of a flame:

66. What is observed on a glass plate when it is introduced into the luminous zone of a candle flame?

67 / 100

Category: Innermost zone: Unburnt wax vapors (black)

67. (A) The innermost zone of a candle flame contains unburnt wax vapors.
(R) This zone appears black due to the presence of unburnt carbon particles.

68 / 100

Category: Innermost zone: Unburnt wax vapors (black)

68. Which zone of the candle flame consists of unburnt wax vapors?

69 / 100

Category: Middle zone: Partial combustion (yellow)

69. Why is the middle zone of a candle flame yellow in color?

70 / 100

Category: Middle zone: Partial combustion (yellow)

70. Why does a blackish ring form on a glass plate when it is introduced into the middle zone of a candle flame?

71 / 100

Category: Outer zone: Complete combustion (blue and hottest)

71. Why do goldsmiths use the outermost zone of the flame to melt gold and silver?

72 / 100

Category: Outer zone: Complete combustion (blue and hottest)

72. Which zone of the flame is the hottest and has complete combustion?

73 / 100

Category: Goldsmith’s use of the outermost zone for melting gold and silver

73. Why do goldsmiths use the outermost zone of a flame for melting gold and silver?

74 / 100

Category: Goldsmith’s use of the outermost zone for melting gold and silver

74. Why do goldsmiths prefer the outermost zone of a flame for melting gold and silver?

75 / 100

Category: What is a Fuel?

75. (A) Charcoal is considered a good fuel because it is readily available and burns easily in air at a moderate rate.
(R) A good fuel is one which is readily available, cheap, burns easily in air at a moderate rate, produces a large amount of heat, and does not leave behind any undesirable substances.

76 / 100

Category: What is a Fuel?

76. Which of the following is NOT a characteristic of a good fuel?

77 / 100

Category: Definition of fuel

77. (A) Wood is considered a fuel because it burns easily in air and produces heat.
(R) A good fuel is one that burns easily in air at a moderate rate and produces a large amount of heat.

78 / 100

Category: Definition of fuel

78. A company is deciding between coal and natural gas for a new power plant. Which of the following factors should they consider to ensure the chosen fuel meets the criteria of a good fuel?

79 / 100

Category: Characteristics of a good fuel:

79. In a laboratory experiment, two fuels are tested for their efficiency. Fuel X produces a large amount of heat but leaves behind ash, while Fuel Y produces less heat but does not leave any residue. Which fuel is more suitable for domestic heating purposes?

80 / 100

Category: Characteristics of a good fuel:

80. Which of the following is a characteristic of a good fuel?

81 / 100

Category: Easily available

81. Consider a fuel that is readily available, cheap, and burns at a moderate rate without leaving any undesirable substances. However, it produces less heat compared to other fuels. Which of the following fuels is most likely to be described by these properties?

82 / 100

Category: Easily available

82. Which of the following substances is considered a fuel?

83 / 100

Category: High calorific value

83. A fuel has a calorific value of 50000 $kJ/kg$. Which of the following could be this fuel?

84 / 100

Category: High calorific value

84. If 1 kg of a fuel produces 45000 $kJ$ of heat energy on complete combustion, which fuel is most likely being referred to?

85 / 100

Category: No harmful emissions

85. Which fuel has the highest calorific value among the given options?

86 / 100

Category: No harmful emissions

86. Which of the following fuels is considered a cleaner fuel due to its minimal harmful emissions?

87 / 100

Category: Classification of fuels:

87. Which of the following properties is NOT desirable for a good fuel?

88 / 100

Category: Classification of fuels:

88. Which of the following is a solid fuel?

89 / 100

Category: Solid fuels: Coal, wood

89. (A) Wood is considered a solid fuel because it is readily available and burns easily in air at a moderate rate.
(R) Wood is classified as a solid fuel due to its physical state and its ability to produce a large amount of heat when burned.

90 / 100

Category: Solid fuels: Coal, wood

90. Which fuel has the highest calorific value among the given options?

91 / 100

Category: Liquid fuels: Kerosene, petrol

91. Which of the following is a characteristic of a good fuel?

92 / 100

Category: Gaseous fuels: CNG, LPG

92. (A) CNG is considered a sustainable fuel for automobiles because it produces fewer harmful emissions.
(R) The calorific value of CNG is higher than that of petrol and diesel, making it a more efficient fuel.

93 / 100

Category: Fuel Efficiency

93. A factory needs to choose a fuel for its boilers based on calorific value and cost. The factory has three options: Cow dung cake 0.5/kg, Coal 1.2/kg, and LPG 2.5/kg. Given the calorific values of these fuels are 7000 kJ/kg, 29000 kJ/kg, and 55000 kJ/kg respectively, which fuel should the factory choose to maximize energy output per dollar spent?

94 / 100

Category: Burning of Fuels Leads to Harmful Products

94. (A) Burning coal in a closed room produces carbon monoxide, which is a poisonous gas.
(R) Carbon monoxide is formed due to the incomplete combustion of coal.

95 / 100

Category: Environmental Impact of Burning Fuels

95. (A) The replacement of diesel and petrol with CNG in automobiles reduces the emission of harmful gases like carbon monoxide and sulphur dioxide.
(R) CNG is a cleaner fuel because it produces harmful products in very small amounts compared to diesel and petrol.

96 / 100

Category: Air pollution and harmful products of combustion:

96. Burning of which fuels releases oxides of sulphur and nitrogen that contribute to acid rain?

97 / 100

Category: Unburnt carbon particles → Cause respiratory diseases like asthma

97. Which of the following is a health issue caused by unburnt carbon particles in the air?

98 / 100

Category: Incomplete combustion → Produces carbon monoxide (poisonous gas)

98. Why is it dangerous to burn coal in a closed room?

99 / 100

Category: Carbon dioxide emissions → Leads to global warming

99. Which of the following is a direct consequence of global warming?

100 / 100

Category: Sulfur dioxide & nitrogen oxides → Cause acid rain

100. Why is CNG (Compressed Natural Gas) considered a cleaner fuel compared to diesel and petrol?

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