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Question (21)

QN001141

The three conditions necessary for combustion together form the

(A) oxygen cycle
(B) fire triangle
(C) heat chain
(D) combustion square

Correct Answer: B

Explanation:

Fuel, heat, and oxygen form the fire triangle.

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Question (22)

QN001142

Which combination represents the fire triangle correctly?

(A) Fuel, oxygen, heat
(B) Water, oxygen, heat
(C) Fuel, carbon dioxide, light
(D) Wax, air, smoke

Correct Answer: A

Explanation:

Combustion requires fuel, heat, and oxygen.

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Question (23)

QN001143

Which of the following situations best demonstrates ignition temperature?

(A) Ice melting in sunlight
(B) Candle wax solidifying
(C) Paper burning after heating with focused sunlight
(D) Water boiling in a vessel

Correct Answer: C

Explanation:

Paper burns after reaching ignition temperature.

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Question (24)

QN001144

Which process below involves formation of a completely new substance?

(A) Tearing paper
(B) Rusting of iron
(C) Melting butter
(D) Folding cloth

Correct Answer: B

Explanation:

Rusting forms iron oxide.

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Question (25)

QN001145

Why is rusting considered irreversible in daily life?

(A) Iron disappears completely
(B) Original iron cannot be easily obtained back
(C) Rust evaporates quickly
(D) Rust becomes water

Correct Answer: B

Explanation:

Rusting permanently changes iron into rust.

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Question (26)

QN001146

Which process produces both heat and light visibly?

(A) Burning magnesium ribbon
(B) Melting wax
(C) Condensation
(D) Dissolving salt in water

Correct Answer: A

Explanation:

Magnesium burns with bright white light and heat.

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Question (27)

QN001147

Which observation is most closely associated with combustion?

(A) Formation of ice crystals
(B) Production of heat
(C) Decrease in volume only
(D) Folding of material

Correct Answer: B

Explanation:

Combustion releases heat energy.

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Question (28)

QN001148

A student says oxygen is necessary for combustion. Which activity supports this statement?

(A) Melting ice
(B) Covering a burning candle with a glass tumbler
(C) Crushing chalk
(D) Folding paper fan

Correct Answer: B

Explanation:

The flame goes out when oxygen supply is cut off.

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Question (29)

QN001149

Which statement about combustible substances is correct?

(A) They cannot burn in air
(B) They undergo combustion reactions
(C) They always remain solid
(D) They never produce heat

Correct Answer: B

Explanation:

Combustible substances burn in air.

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Question (30)

QN001150

Which of the following is NOT a combustible substance?

(A) Cotton
(B) Paper
(C) Kerosene
(D) Glass

Correct Answer: D

Explanation:

Glass does not burn easily.

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Question (21)

The three conditions necessary for combustion together form the

Explanation:

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Question (22)

Which combination represents the fire triangle correctly?

Explanation:

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Question (23)

Which of the following situations best demonstrates ignition temperature?

Explanation:

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Question (24)

Which process below involves formation of a completely new substance?

Explanation:

Link:

Question (25)

Why is rusting considered irreversible in daily life?

Explanation:

Link:

Question (26)

Which process produces both heat and light visibly?

Explanation:

Link:

Question (27)

Which observation is most closely associated with combustion?

Explanation:

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Question (28)

A student says oxygen is necessary for combustion. Which activity supports this statement?

Explanation:

Link:

Question (29)

Which statement about combustible substances is correct?

Explanation:

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Question (30)

Which of the following is NOT a combustible substance?

Explanation:

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