Combustion and Flame — Class 8 MCQs with Answers
Class 8 CBSE Science · Chapter 104
Pre-2026 syllabusThis chapter is from the older NCERT book. See the 2026-27 Class 8 Science chapters →
72 practice questions · 24 Easy · 24 Medium · 24 Hard · Updated
Practise the most important Class 8 CBSE Science questions from Chapter 104, "Combustion and Flame". You get 6 timed quizzes made from 72 NCERT-based MCQs, with answers and explanations. The questions are split into 24 Easy, 24 Medium and 24 Hard. Warm up on the basics, then move on to the exam-level questions that set top scorers in CBSE Board exams apart.
To score well in "Combustion and Flame", focus on clear concepts in physics, chemistry and biology basics. Each MCQ here is timed and uses exam-style marking (+4 correct, −1 wrong, 0 skipped). This trains you to stay accurate under time pressure, as real papers need. Every question has a short explanation, so a wrong answer becomes a quick lesson. It is the fastest way to fix gaps before a test.
Use this chapter for focused revision. Start with the Easy set to check your basics on Combustion and Flame, then move to Medium and Hard to practise applying them. Your accuracy, streaks and XP save automatically. This chapter also adds to your overall Class 8 Science mastery score. 14 sample questions are solved in full below, with the answer and a worked explanation. Sign in free to start practising.
Key concepts: Combustion and Flame (Class 8 Science)
This chapter covers combustion, the conditions and types of burning, the structure of a flame, and fuels with their efficiency.
- Combustion
- A chemical process in which a substance reacts with oxygen, giving out heat (and often light).
- Conditions for combustion
- A combustible substance, a supporter (oxygen), and reaching the ignition temperature.
- Types of combustion
- Rapid (e.g. burning gas), spontaneous (e.g. phosphorus) and explosive (e.g. firecrackers).
- Structure of a flame
- Three zones — the innermost (unburnt, dark), middle (yellow, partial combustion) and outermost (blue, complete combustion, hottest).
Combustion and Flame — important questions & MCQs with answers (Class 8 Science)
14 solved questions from this chapter's difficulty levels, each with its answer and explanation. The other 58 are timed and scored when you sign in.
- Q1Easy
Combustion is a chemical process in which a substance reacts with:
A.NitrogenB.Carbon dioxideC.Oxygen, giving out heat✓ CorrectD.WaterAnswer: C. Oxygen, giving out heat
Explanation: In combustion a substance reacts with oxygen to produce heat (and often light).
- Q2Easy
Burning of LPG in a stove is an example of:
A.Spontaneous combustionB.Rapid combustion✓ CorrectC.ExplosionD.No combustionAnswer: B. Rapid combustion
Explanation: LPG burns rapidly, producing heat and light at once — rapid combustion.
- Q3Easy
Which part of a candle flame is the hottest?
A.Innermost dark zoneB.Middle yellow zoneC.Outermost blue zone✓ CorrectD.The wickAnswer: C. Outermost blue zone
Explanation: The outer blue zone has complete combustion and is the hottest part of the flame.
- Q4Easy
The amount of heat produced on complete burning of 1 kg of a fuel is its:
A.Calorific value✓ CorrectB.Ignition temperatureC.Boiling pointD.DensityAnswer: A. Calorific value
Explanation: Calorific value is the heat (in kJ/kg) released by completely burning 1 kg of a fuel.
- Q5Easy
Which is commonly used to put out small ordinary fires (wood, paper)?
A.PetrolB.OilC.KeroseneD.Water✓ CorrectAnswer: D. Water
Explanation: Water cools the fuel below ignition temperature and cuts off oxygen for ordinary fires.
- Q6Easy
The lowest temperature at which a substance catches fire is its:
A.Melting pointB.Ignition temperature✓ CorrectC.Boiling pointD.Freezing pointAnswer: B. Ignition temperature
Explanation: The ignition temperature is the lowest temperature at which a substance starts burning.
- Q7Medium
A burning candle covered with a glass tumbler soon goes out because:
A.The wax finishesB.The temperature falls suddenlyC.Water formsD.The oxygen inside is used up✓ CorrectAnswer: D. The oxygen inside is used up
Explanation: The trapped oxygen gets used up, and without oxygen combustion cannot continue.
- Q8Medium
Forest fires can sometimes start by spontaneous combustion when:
A.It rainsB.The air is coldC.Dry material reaches its ignition temperature due to heat✓ CorrectD.Trees absorb waterAnswer: C. Dry material reaches its ignition temperature due to heat
Explanation: Intense heat can raise dry leaves/wood to their ignition temperature, starting a fire on its own.
- Q9Medium
Why does charcoal glow but does not produce a flame, while a candle gives a flame?
A.Charcoal has no carbonB.Charcoal does not vaporise, while candle wax vaporises and burns as a flame✓ CorrectC.Charcoal is wetD.Candles have no fuelAnswer: B. Charcoal does not vaporise, while candle wax vaporises and burns as a flame
Explanation: Only vaporising fuels burn with a flame; non-vaporising charcoal merely glows.
- Q10Medium
Why is CNG considered a better fuel than wood?
A.It is cheaper than woodB.It has a higher calorific value and burns cleanly✓ CorrectC.It is a solidD.It produces more smokeAnswer: B. It has a higher calorific value and burns cleanly
Explanation: CNG releases more heat per kg and burns more completely with less pollution than wood.
- Q11Medium
Why does blowing air on a weak fire make it burn better, but blowing hard on a candle puts it out?
A.A weak fire gets more oxygen; a strong blow cools the candle below its ignition temperature and removes vapour✓ CorrectB.Air adds fuelC.Air is coldD.Both reactions are the sameAnswer: A. A weak fire gets more oxygen; a strong blow cools the candle below its ignition temperature and removes vapour
Explanation: Gentle air feeds oxygen; a hard blast cools the wick below ignition temperature and blows away fuel vapour.
- Q12Hard
Assertion (A): A candle goes out when covered by a glass jar. Reason (R): Combustion needs a continuous supply of oxygen. Choose the correct option.
A.A is true, R is falseB.A is false, R is trueC.Both A and R are true and R explains A✓ CorrectD.Both A and R are falseAnswer: C. Both A and R are true and R explains A
Explanation: The jar cuts off oxygen; since combustion needs oxygen, the candle goes out — R explains A.
- Q13Hard
Match: (i) LPG burning (ii) Phosphorus catching fire in air (iii) Firecracker bursting.
A.i-explosion, ii-rapid, iii-spontaneousB.i-spontaneous, ii-explosion, iii-rapidC.i-rapid, ii-spontaneous, iii-explosion✓ CorrectD.i-rapid, ii-explosion, iii-spontaneousAnswer: C. i-rapid, ii-spontaneous, iii-explosion
Explanation: LPG – rapid combustion, phosphorus – spontaneous, firecracker – explosion.
- Q14Hard
A goldsmith heats gold using the outer blue zone of a flame rather than the bright yellow zone because the blue zone:
A.Is the coolestB.Has unburnt carbonC.Has no oxygenD.Undergoes complete combustion and is the hottest✓ CorrectAnswer: D. Undergoes complete combustion and is the hottest
Explanation: Complete combustion in the outer zone makes it hottest, best for melting metals.
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Start this chapter free →Combustion and Flame — FAQs
What are the key concepts in Class 8 Science Combustion and Flame?+
This chapter covers combustion, the conditions and types of burning, the structure of a flame, and fuels with their efficiency. Key ideas include Combustion, Conditions for combustion, Types of combustion, Structure of a flame.
What does Class 8 Science Chapter 104 (Combustion and Flame) cover on XamBaaz?+
It has 72 NCERT-based MCQs on "Combustion and Flame": 24 Easy, 24 Medium and 24 Hard. Together they make 6 timed quizzes, and you never get the same set twice. Every question has an instant explanation. They help you prepare for CBSE Board exams.
Are these "Combustion and Flame" questions free to practise?+
Yes. Sign in with Google to practise "Combustion and Flame" free. Full unlimited access is ₹999/year on a launch offer until 1 December 2026. No chapter is charged separately.
How should I revise "Combustion and Flame" for the exam?+
Start with the Easy quiz to check your basics, then try Medium and Hard to practise applying them. There are 6 timed quizzes on this chapter, so you can come back for a fresh set instead of one you have seen. Read each explanation, retry the questions you miss, and track your accuracy until it stays high.
Are these "Combustion and Flame" MCQs available with answers?+
Yes. 14 sample questions are shown here in full, each with the correct option and a step-by-step "Why" explanation. Sign in free with Google to start practising, with instant scoring.
Is there negative marking in the "Combustion and Flame" quizzes?+
Yes. The timed quizzes use exam-style marking: +4 for a right answer, −1 for a wrong one and 0 for a skip. MHT-CET and CBSE board papers have no negative marking. Our mocks for those are scored their way.
What are the important questions from Combustion and Flame (Class 8 Science)?+
The questions that matter most test Combustion, Conditions for combustion, Types of combustion, Structure of a flame. This page shows 14 solved important MCQs with answers and explanations; all 72 questions on the chapter are available as timed quizzes once you sign in.
Is there an online quiz for Combustion and Flame?+
Yes — Class 8 Science Combustion and Flame has timed online quizzes at Easy, Medium and Hard levels, with instant scoring and a worked explanation on every question. The first quiz on the chapter is free.