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Combustion and Flame — Class 8 CBSE Science MCQs with Solutions
Free Class 8 CBSE Science Combustion and Flame MCQs with step-by-step solutions. Practise online on Prepizo — no login needed.
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Sample questions with solutions
Q1 — easy
Which gas is essential for combustion?
A. Nitrogen
B. Oxygen ✓ Correct
C. Carbon dioxide
D. Hydrogen
Solution: Oxygen is the supporter of combustion.
Q2 — easy
The most commonly used fire extinguisher for ordinary fires is:
A. petrol
B. water ✓ Correct
C. kerosene
D. oil
Solution: Water cools the fuel below its ignition temperature.
Q3 — easy
Which zone of a candle flame is the hottest?
A. dark inner zone
B. luminous middle zone
C. non-luminous outer zone ✓ Correct
D. the wick
Solution: The outer zone has complete combustion.
Q4 — hard
The dark inner zone of a candle flame contains:
A. completely burnt gases
B. unburnt wax vapours ✓ Correct
C. only oxygen
D. carbon dioxide only
Solution: It lacks oxygen, so wax vapour remains unburnt.
Q5 — hard
Goldsmiths use the outermost zone of the flame because it:
A. is the coolest
B. is the hottest and has complete combustion ✓ Correct
C. produces most smoke
D. has no oxygen
Solution: The non-luminous outer zone is hottest.
Q6 — hard
Excess carbon dioxide in the atmosphere from burning fuels leads mainly to:
A. acid rain
B. global warming ✓ Correct
C. ozone hole
D. water pollution
Solution: CO₂ is the main greenhouse gas driving global warming.
Q7 — medium
The substances that vaporise during burning give a:
A. flame ✓ Correct
B. only glow
C. no light
D. smoke only
Solution: Only vaporising substances produce a flame.
Q8 — medium
Carbon dioxide is a good fire extinguisher because it:
A. is lighter than air
B. forms a blanket cutting off oxygen supply ✓ Correct
C. burns quickly
D. raises the temperature
Solution: CO₂ is heavier than air and cuts off oxygen.
Q9 — medium
The amount of heat energy produced by complete burning of 1 kg of a fuel is its:
A. ignition temperature
B. calorific value ✓ Correct
C. melting point
D. density
Solution: That is the definition of calorific value.