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Question (11)

QN0029823

A student observed steam turning into water droplets on a cool plate. This change is called

(A) evaporation
(B) rusting
(C) condensation
(D) combustion

Correct Answer: C

Explanation:

Water vapour cools and changes back into liquid water.

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Question (12)

QN0029824

Which process below is a slow undesirable change affecting metals?

(A) Rusting
(B) Melting
(C) Freezing
(D) Folding

Correct Answer: A

Explanation:

Rusting damages iron objects gradually.

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Question (13)

QN0029825

Which statement about reversible changes is correct?

(A) They always form new substances
(B) They can return to the original state
(C) They are always chemical changes
(D) They are always permanent

Correct Answer: B

Explanation:

Reversible changes can often be undone.

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Question (14)

QN0029826

Why is compost preparation considered beneficial for society?

(A) It increases plastic waste
(B) It pollutes water sources
(C) It converts waste into useful manure
(D) It destroys soil nutrients

Correct Answer: C

Explanation:

Compost enriches soil fertility.

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Question (15)

QN0029827

Which example best represents an undesirable chemical change?

(A) Cooking food
(B) Digestion of food
(C) Rusting of bridges
(D) Formation of curd

Correct Answer: C

Explanation:

Rust weakens structures and causes damage.

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Question (16)

QN0029828

Which process below changes the Earth’s surface gradually over time?

(A) Explosion of crackers
(B) Soil erosion by rivers
(C) Breaking chalk
(D) Burning paper

Correct Answer: B

Explanation:

Flowing water slowly removes soil and shapes landforms.

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Question (17)

QN0029829

A candle became shorter after burning for two hours. Which explanation is correct?

(A) Only physical change occurred
(B) Only chemical change occurred
(C) Both physical and chemical changes occurred
(D) No change occurred

Correct Answer: C

Explanation:

Wax melts physically and burns chemically.

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Question (18)

QN0029830

Which process below is reversible because no new substance forms?

(A) Cooking rice
(B) Burning wood
(C) Melting ice
(D) Rusting iron

Correct Answer: C

Explanation:

Ice and water are the same substance.

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Question (19)

QN0029831

Which condition mainly increases the rate of rusting near coastal regions?

(A) Dry air
(B) Moist salty air
(C) Lack of oxygen
(D) Low humidity only

Correct Answer: B

Explanation:

Salt and moisture speed up rusting.

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Question (20)

QN0029832

Which example best shows that some natural changes are useful to humans?

(A) Flood damage
(B) Soil formation from rocks
(C) Cracking of roads
(D) Food spoilage

Correct Answer: B

Explanation:

Soil supports plant growth and agriculture.

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Question (11)

A student observed steam turning into water droplets on a cool plate. This change is called

Explanation:

Link:

Question (12)

Which process below is a slow undesirable change affecting metals?

Explanation:

Link:

Question (13)

Which statement about reversible changes is correct?

Explanation:

Link:

Question (14)

Why is compost preparation considered beneficial for society?

Explanation:

Link:

Question (15)

Which example best represents an undesirable chemical change?

Explanation:

Link:

Question (16)

Which process below changes the Earth’s surface gradually over time?

Explanation:

Link:

Question (17)

A candle became shorter after burning for two hours. Which explanation is correct?

Explanation:

Link:

Question (18)

Which process below is reversible because no new substance forms?

Explanation:

Link:

Question (19)

Which condition mainly increases the rate of rusting near coastal regions?

Explanation:

Link:

Question (20)

Which example best shows that some natural changes are useful to humans?

Explanation:

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