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Question (11)

QN001091

Which observation confirms burning magnesium ribbon is a chemical change?

(A) Ribbon becomes shorter
(B) Heat and light are produced with a new substance
(C) Shape changes only
(D) Ribbon melts completely

Correct Answer: B

Explanation:

Burning magnesium forms magnesium oxide along with heat and light.

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Question (12)

QN001092

Combustion is a chemical reaction in which a substance reacts with

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

Correct Answer: C

Explanation:

Combustion occurs in the presence of oxygen.

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Question (13)

QN001093

Which of the following is a combustible substance?

(A) Water
(B) Glass
(C) Wood
(D) Sand

Correct Answer: C

Explanation:

Wood burns in air and is combustible.

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Question (14)

QN001094

Which condition is necessary for combustion?

(A) Absence of oxygen
(B) Presence of ice
(C) Presence of oxygen
(D) Presence of salt water

Correct Answer: C

Explanation:

Oxygen supports combustion.

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Question (15)

QN001095

A candle covered with a glass tumbler stops burning because

(A) wax finishes immediately
(B) oxygen supply becomes insufficient
(C) the tumbler absorbs heat
(D) carbon dioxide burns the flame

Correct Answer: B

Explanation:

The supply of oxygen gets cut off.

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Question (16)

QN001096

The gas produced inside the tumbler during candle burning can be tested using

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

Correct Answer: C

Explanation:

Carbon dioxide turns lime water milky.

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Question (17)

QN001097

Which statement correctly defines ignition temperature?

(A) Highest temperature produced during burning
(B) Minimum temperature at which a substance catches fire
(C) Temperature of melting
(D) Temperature at which water boils

Correct Answer: B

Explanation:

Ignition temperature is the minimum temperature needed for burning.

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Question (18)

QN001098

A paper catches fire quickly when touched by a burning matchstick because

(A) paper contains oxygen
(B) the matchstick temperature is above paper’s ignition temperature
(C) paper melts first
(D) air cools the paper

Correct Answer: B

Explanation:

The matchstick provides enough heat to reach ignition temperature.

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Question (19)

QN001099

Focusing sunlight on paper using a magnifying glass causes burning because

(A) sunlight removes oxygen
(B) the paper becomes wet
(C) the paper reaches ignition temperature
(D) carbon dioxide is absorbed

Correct Answer: C

Explanation:

Concentrated sunlight heats the paper sufficiently.

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Question (20)

QN001100

Which of the following is NOT required for combustion?

(A) Oxygen
(B) Fuel
(C) Heat
(D) Nitrogen

Correct Answer: D

Explanation:

Nitrogen does not support combustion.

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Question (11)

Which observation confirms burning magnesium ribbon is a chemical change?

Explanation:

Link:

Question (12)

Combustion is a chemical reaction in which a substance reacts with

Explanation:

Link:

Question (13)

Which of the following is a combustible substance?

Explanation:

Link:

Question (14)

Which condition is necessary for combustion?

Explanation:

Link:

Question (15)

A candle covered with a glass tumbler stops burning because

Explanation:

Link:

Question (16)

The gas produced inside the tumbler during candle burning can be tested using

Explanation:

Link:

Question (17)

Which statement correctly defines ignition temperature?

Explanation:

Link:

Question (18)

A paper catches fire quickly when touched by a burning matchstick because

Explanation:

Link:

Question (19)

Focusing sunlight on paper using a magnifying glass causes burning because

Explanation:

Link:

Question (20)

Which of the following is NOT required for combustion?

Explanation:

Link:

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