WAEC Physics Past Questions & Answers - Page 308

1,536.

A block of ice at its melting point is left on a table in the atmosphere and observed to melt gradually. Which of the following statements is true about the melting process?

A.

the reaction force of the table on the ice breaks the ice into water molecules

B.

heat extracted from the ice block makes the ice block cold

C.

the ice block absorbs heat from the atmosphere and its temperature rises

D.

the atmosphere absorbs heat from the ice block and its temperature falls

E.

the ice block absorbs heat from the atmosphere and its temperature remains constant as it melts

Correct answer is E

The heat of fusion is the quantity of heat necessary to change of a solid to a liquid with no temperature change

1,537.
1,538.

Which of the following substance is not a good conductor of electricity?

A.

Human body

B.

Glass

C.

Aluminium

D.

Earth

E.

Copper

Correct answer is B

No explanation has been provided for this answer.

1,539.

Water in an open container boils at a lower temperature when heated at the top of a mountain than at sea-level because at the top of a mountain the

A.

relative humidity is higher than at sea-level

B.

rays of the sun adds more heat to the water

C.

temperature is lower than that at sea-level

D.

pressure is lower than that at sea-level

E.

pressure is more than that at sea-level

Correct answer is D

Refer to Elementary physics, pressure reduces with height.

1,540.

Which of the following statements is/are not correct?

A.

Evaporation takes place only at the surface of the liquid

B.

Boiling takes place throughout the volume of the liquid

C.

Evaportaion takes place at all temperatures

D.

Boiling takes place at a particular temperature for a liquid at a fixed external pressure

E.

The boiling point of a liquid is not affected by impurities

Correct answer is E

No explanation has been provided for this answer.