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Question (21)

QN001101

The three requirements for combustion together form the

(A) fire circle
(B) combustion law
(C) fire triangle
(D) heat cycle

Correct Answer: C

Explanation:

Fuel, oxygen, and heat form the fire triangle.

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Question (22)

QN001102

Which situation best demonstrates a chemical change producing heat and light?

(A) Melting wax
(B) Burning magnesium ribbon
(C) Folding paper
(D) Breaking glass

Correct Answer: B

Explanation:

Magnesium burns with bright light and heat.

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Question (23)

QN001103

Which process in a burning candle is a chemical change?

(A) Melting wax
(B) Solidification of wax
(C) Evaporation of wax
(D) Burning of wax vapour

Correct Answer: D

Explanation:

Burning wax vapour forms new substances.

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Question (24)

QN001104

Which processes in a burning candle are physical changes?

(A) Only burning of vapour
(B) Melting and evaporation of wax
(C) Formation of carbon dioxide only
(D) Burning of wick only

Correct Answer: B

Explanation:

Melting and evaporation change only the state of wax.

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Question (25)

QN001105

The burning of a candle involves

(A) only physical changes
(B) only chemical changes
(C) both physical and chemical changes
(D) no change at all

Correct Answer: C

Explanation:

Wax melts physically and burns chemically.

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Question (26)

QN001106

Which scientist delivered lectures titled “Chemical History of a Candle”?

(A) Isaac Newton
(B) Albert Einstein
(C) Michael Faraday
(D) C. V. Raman

Correct Answer: C

Explanation:

Michael Faraday gave the famous lectures.

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Question (27)

QN001107

Fireflies produce light due to

(A) reflection of sunlight
(B) a chemical change
(C) electrical energy
(D) friction

Correct Answer: B

Explanation:

The light is produced by a chemical process.

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Question (28)

QN001108

Light produced in living organisms without heat is called

(A) evaporation
(B) respiration
(C) bioluminescence
(D) combustion

Correct Answer: C

Explanation:

Bioluminescence is light production without heat.

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Question (29)

QN001109

Which method is safest to extinguish fire on a person’s clothes according to the chapter?

(A) Pour kerosene
(B) Use synthetic cloth
(C) Wrap with a blanket to cut off air supply
(D) Blow air strongly

Correct Answer: C

Explanation:

Cutting off oxygen extinguishes the fire.

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Question (30)

QN001110

Synthetic blankets should not be used to extinguish fire because they

(A) absorb oxygen
(B) melt and stick to skin
(C) increase carbon dioxide
(D) produce water vapour

Correct Answer: B

Explanation:

Synthetic materials can melt during fire.

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Question (21)

The three requirements for combustion together form the

Explanation:

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Question (22)

Which situation best demonstrates a chemical change producing heat and light?

Explanation:

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Question (23)

Which process in a burning candle is a chemical change?

Explanation:

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Question (24)

Which processes in a burning candle are physical changes?

Explanation:

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Question (25)

The burning of a candle involves

Explanation:

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Question (26)

Which scientist delivered lectures titled “Chemical History of a Candle”?

Explanation:

Link:

Question (27)

Fireflies produce light due to

Explanation:

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Question (28)

Light produced in living organisms without heat is called

Explanation:

Link:

Question (29)

Which method is safest to extinguish fire on a person’s clothes according to the chapter?

Explanation:

Link:

Question (30)

Synthetic blankets should not be used to extinguish fire because they

Explanation:

Link:

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