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Question (1)

QN0029813

A student kept an iron nail in water for several days and observed a reddish-brown layer on it. Which condition mainly caused this change?

(A) Presence of oxygen and moisture
(B) Presence of sunlight only
(C) Presence of salt only
(D) Presence of heat only

Correct Answer: A

Explanation:

Rusting occurs when iron reacts with oxygen in the presence of water.

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Question (2)

QN0029814

Which of the following changes is both slow and desirable?

(A) Spoiling of milk
(B) Formation of compost
(C) Rusting of bicycle chain
(D) Cracking of glass

Correct Answer: B

Explanation:

Compost formation improves soil fertility naturally.

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Question (3)

QN0029815

A piece of wax was melted and then cooled into a new shape. Which statement is correct?

(A) A new substance was formed
(B) It is a reversible physical change
(C) It is an undesirable chemical change
(D) Wax was permanently destroyed

Correct Answer: B

Explanation:

Only shape and state changed; wax remained the same substance.

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Question (4)

QN0029816

Which example best shows both physical and chemical changes occurring together?

(A) Dissolving sugar in water
(B) Burning of a candle
(C) Cutting paper
(D) Stretching a rubber band

Correct Answer: B

Explanation:

Wax melts physically while burning of wax is a chemical change.

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Question (5)

QN0029817

Why is food refrigeration useful in homes?

(A) It increases chemical reactions
(B) It prevents undesirable spoilage
(C) It changes food into new substances
(D) It removes nutrients from food

Correct Answer: B

Explanation:

Low temperature slows microbial activity.

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Question (6)

QN0029818

Which of the following is an irreversible physical change?

(A) Freezing water
(B) Melting butter
(C) Breaking a glass bottle
(D) Folding cloth

Correct Answer: C

Explanation:

No new substance forms, but the original shape cannot be restored easily.

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Question (7)

QN0029819

A farmer stores grains in dry containers after sun-drying them. What is the main purpose of this practice?

(A) To increase grain moisture
(B) To prevent spoilage by fungi and insects
(C) To change grains chemically
(D) To reduce grain size

Correct Answer: B

Explanation:

Moisture encourages fungal growth and spoilage.

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Question (8)

QN0029820

Which process below contributes directly to soil formation in nature?

(A) Burning coal
(B) Weathering of rocks
(C) Melting metals
(D) Freezing milk

Correct Answer: B

Explanation:

Rocks slowly break into smaller particles to form soil.

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Question (9)

QN0029821

Which observation indicates that a chemical change has occurred?

(A) Change in shape only
(B) Formation of a new substance
(C) Melting without burning
(D) Dissolving without reaction

Correct Answer: B

Explanation:

Chemical changes produce new substances with different properties.

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Question (10)

QN0029822

Which of the following changes is desirable in agriculture?

(A) Soil erosion
(B) Rusting of farming tools
(C) Germination of seeds
(D) Spoiling of crops

Correct Answer: C

Explanation:

Germination leads to growth of new plants.

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Question (1)

A student kept an iron nail in water for several days and observed a reddish-brown layer on it. Which condition mainly caused this change?

Explanation:

Link:

Question (2)

Which of the following changes is both slow and desirable?

Explanation:

Link:

Question (3)

A piece of wax was melted and then cooled into a new shape. Which statement is correct?

Explanation:

Link:

Question (4)

Which example best shows both physical and chemical changes occurring together?

Explanation:

Link:

Question (5)

Why is food refrigeration useful in homes?

Explanation:

Link:

Question (6)

Which of the following is an irreversible physical change?

Explanation:

Link:

Question (7)

A farmer stores grains in dry containers after sun-drying them. What is the main purpose of this practice?

Explanation:

Link:

Question (8)

Which process below contributes directly to soil formation in nature?

Explanation:

Link:

Question (9)

Which observation indicates that a chemical change has occurred?

Explanation:

Link:

Question (10)

Which of the following changes is desirable in agriculture?

Explanation:

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