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Question (11)

QN001131

Which gas in air supports combustion?

(A) Nitrogen
(B) Carbon dioxide
(C) Oxygen
(D) Hydrogen

Correct Answer: C

Explanation:

Oxygen supports burning.

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Question (12)

QN001132

In the candle experiment, the covered candle stops burning because

(A) wax disappears
(B) oxygen gets used up
(C) glass absorbs heat
(D) water vapour increases

Correct Answer: B

Explanation:

The supply of oxygen becomes insufficient.

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Question (13)

QN001133

The uncovered candle continues to burn because it receives a continuous supply of

(A) nitrogen
(B) hydrogen
(C) oxygen
(D) helium

Correct Answer: C

Explanation:

Oxygen from air supports combustion.

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Question (14)

QN001134

Carbon dioxide formed during candle burning can be detected using

(A) vinegar
(B) turmeric solution
(C) lime water
(D) soap solution

Correct Answer: C

Explanation:

Carbon dioxide turns lime water milky.

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Question (15)

QN001135

Lime water turns milky due to the formation of

(A) magnesium oxide
(B) calcium carbonate
(C) sodium chloride
(D) iron oxide

Correct Answer: B

Explanation:

Calcium carbonate causes the milky appearance.

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Question (16)

QN001136

Which statement correctly defines combustion?

(A) A process involving melting only
(B) A chemical reaction producing heat and/or light
(C) A physical change involving oxygen
(D) A process of dissolving substances

Correct Answer: B

Explanation:

Combustion is a chemical reaction releasing heat and/or light.

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Question (17)

QN001137

The lowest temperature at which a substance catches fire is called

(A) boiling point
(B) melting point
(C) ignition temperature
(D) freezing point

Correct Answer: C

Explanation:

Ignition temperature is the minimum temperature needed for burning.

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Question (18)

QN001138

A paper catches fire quickly near a burning matchstick because

(A) paper melts instantly
(B) the matchstick temperature is above paper’s ignition temperature
(C) nitrogen supports burning
(D) paper releases oxygen

Correct Answer: B

Explanation:

The matchstick provides enough heat for ignition.

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Question (19)

QN001139

A magnifying glass can burn paper because it

(A) cools the paper
(B) removes oxygen
(C) concentrates sunlight to raise temperature
(D) changes paper into fuel

Correct Answer: C

Explanation:

Concentrated sunlight raises the paper’s temperature.

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Question (20)

QN001140

Which of the following is NOT essential for combustion?

(A) Fuel
(B) Oxygen
(C) Heat
(D) Carbon dioxide

Correct Answer: D

Explanation:

Carbon dioxide does not support combustion.

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Question (11)

Which gas in air supports combustion?

Explanation:

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Question (12)

In the candle experiment, the covered candle stops burning because

Explanation:

Link:

Question (13)

The uncovered candle continues to burn because it receives a continuous supply of

Explanation:

Link:

Question (14)

Carbon dioxide formed during candle burning can be detected using

Explanation:

Link:

Question (15)

Lime water turns milky due to the formation of

Explanation:

Link:

Question (16)

Which statement correctly defines combustion?

Explanation:

Link:

Question (17)

The lowest temperature at which a substance catches fire is called

Explanation:

Link:

Question (18)

A paper catches fire quickly near a burning matchstick because

Explanation:

Link:

Question (19)

A magnifying glass can burn paper because it

Explanation:

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Question (20)

Which of the following is NOT essential for combustion?

Explanation:

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