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Question (11)

QN00191

Which of the following is an example of convection in gases?

(A) Heating an iron nail
(B) Hot tea warming a steel spoon
(C) Smoke rising from firewood
(D) Sunlight reaching Earth

Correct Answer: C

Explanation:

Rising smoke is caused by hot air currents.

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Question (12)

QN00192

In the beaker experiment, potassium permanganate is used mainly to —

(A) cool the water
(B) colour the beaker
(C) show the movement of water
(D) increase the boiling point

Correct Answer: C

Explanation:

The coloured streak helps observe water movement.

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Question (13)

QN00193

In convection, heat transfer occurs due to movement of —

(A) energy only
(B) solid particles only
(C) particles of fluids
(D) light waves only

Correct Answer: C

Explanation:

Fluids transfer heat by moving particles.

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Question (14)

QN00194

When air above a flame gets heated, it —

(A) becomes denser
(B) contracts
(C) rises upward
(D) changes into smoke

Correct Answer: C

Explanation:

Heated air becomes lighter and rises.

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Question (15)

QN00195

Why is convection not possible in solids?

(A) Solids absorb no heat
(B) Solid particles cannot move freely
(C) Solids are transparent
(D) Solids contain no particles

Correct Answer: B

Explanation:

Solid particles remain fixed in position.

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Question (16)

QN00196

In coastal regions during daytime, cooler air moves from sea towards land. This is called —

(A) land breeze
(B) convection current
(C) sea breeze
(D) radiation current

Correct Answer: C

Explanation:

Sea breeze blows from sea to land during daytime.

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Question (17)

QN00197

Sea breeze occurs because during daytime —

(A) sea heats faster than land
(B) land heats faster than sea
(C) both heat equally
(D) sea becomes lighter

Correct Answer: B

Explanation:

Land heats faster and warm air rises.

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Question (18)

QN00198

At night, land breeze occurs because land becomes cooler than sea —

(A) slowly
(B) at the same rate
(C) more quickly
(D) never

Correct Answer: C

Explanation:

Land cools faster than water at night.

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Question (19)

QN00199

During land breeze, air moves from —

(A) sea to land
(B) land to sea
(C) mountains to plains
(D) plains to mountains

Correct Answer: B

Explanation:

Cooler air moves from land towards sea.

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Question (20)

QN00200

In Activity 7.4, soil becomes hotter than water after equal heating because soil —

(A) heats faster than water
(B) contains air
(C) reflects sunlight
(D) absorbs no heat

Correct Answer: A

Explanation:

Soil heats more quickly than water.

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Question (11)

Which of the following is an example of convection in gases?

Explanation:

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Question (12)

In the beaker experiment, potassium permanganate is used mainly to —

Explanation:

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Question (13)

In convection, heat transfer occurs due to movement of —

Explanation:

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Question (14)

When air above a flame gets heated, it —

Explanation:

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Question (15)

Why is convection not possible in solids?

Explanation:

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Question (16)

In coastal regions during daytime, cooler air moves from sea towards land. This is called —

Explanation:

Link:

Question (17)

Sea breeze occurs because during daytime —

Explanation:

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Question (18)

At night, land breeze occurs because land becomes cooler than sea —

Explanation:

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Question (19)

During land breeze, air moves from —

Explanation:

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Question (20)

In Activity 7.4, soil becomes hotter than water after equal heating because soil —

Explanation:

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