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Question (31)

QN001151

Wrapping a blanket around a person whose clothes caught fire helps because it

(A) cools the body instantly
(B) supplies more oxygen
(C) cuts off the air supply
(D) melts the flames

Correct Answer: C

Explanation:

Fire goes out when oxygen supply is stopped.

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Question (32)

QN001152

Synthetic blankets should not be used during fire accidents because they

(A) absorb water
(B) produce oxygen
(C) melt and stick to skin
(D) increase cooling rapidly

Correct Answer: C

Explanation:

Synthetic materials melt on heating.

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Question (33)

QN001153

Fireflies produce light through a process called

(A) evaporation
(B) reflection
(C) bioluminescence
(D) condensation

Correct Answer: C

Explanation:

Fireflies glow due to bioluminescence.

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Question (34)

QN001154

Bioluminescence is light production in living organisms without producing much

(A) oxygen
(B) smoke
(C) heat
(D) nitrogen

Correct Answer: C

Explanation:

Bioluminescence produces very little heat.

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Question (35)

QN001155

Which of the following changes involves oxygen directly reacting with another substance?

(A) Folding paper
(B) Rusting iron
(C) Melting wax
(D) Boiling water

Correct Answer: B

Explanation:

Oxygen reacts with iron during rusting.

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Question (36)

QN001156

The candle flame goes out after some time inside a covered tumbler mainly because

(A) wax becomes cold
(B) oxygen inside gets exhausted
(C) the tumbler melts
(D) smoke absorbs light

Correct Answer: B

Explanation:

Combustion stops when oxygen is exhausted.

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Question (37)

QN001157

Which of the following best explains why heat is necessary for combustion?

(A) Heat increases oxygen content
(B) Heat helps fuel reach ignition temperature
(C) Heat converts oxygen into fuel
(D) Heat removes carbon dioxide

Correct Answer: B

Explanation:

Fuel burns only after reaching ignition temperature.

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Question (38)

QN001158

Which example from the chapter combines chemical change with practical safety knowledge?

(A) Folding paper boats
(B) Burning magnesium ribbon
(C) Using blankets to extinguish fire
(D) Melting candle wax

Correct Answer: C

Explanation:

Cutting off oxygen is an important fire safety method.

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Question (39)

QN001159

Burning magnesium ribbon in air demonstrates that oxygen from air

(A) prevents reactions
(B) supports combustion
(C) reduces ignition temperature to zero
(D) changes into nitrogen

Correct Answer: B

Explanation:

Oxygen supports burning.

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Question (40)

QN001160

Which process from the chapter is both a chemical change and an oxidation process?

(A) Boiling water
(B) Melting ice
(C) Rusting of iron
(D) Folding paper

Correct Answer: C

Explanation:

Rusting involves oxidation of iron.

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Question (31)

Wrapping a blanket around a person whose clothes caught fire helps because it

Explanation:

Link:

Question (32)

Synthetic blankets should not be used during fire accidents because they

Explanation:

Link:

Question (33)

Fireflies produce light through a process called

Explanation:

Link:

Question (34)

Bioluminescence is light production in living organisms without producing much

Explanation:

Link:

Question (35)

Which of the following changes involves oxygen directly reacting with another substance?

Explanation:

Link:

Question (36)

The candle flame goes out after some time inside a covered tumbler mainly because

Explanation:

Link:

Question (37)

Which of the following best explains why heat is necessary for combustion?

Explanation:

Link:

Question (38)

Which example from the chapter combines chemical change with practical safety knowledge?

Explanation:

Link:

Question (39)

Burning magnesium ribbon in air demonstrates that oxygen from air

Explanation:

Link:

Question (40)

Which process from the chapter is both a chemical change and an oxidation process?

Explanation:

Link:

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