WAEC Physics Past Questions & Answers - Page 268

1,336.

How much heat is required to convert 20 g of ice at 0oC to water at the same temperature? (Specific latent heat of ice = 336 J g-1)

A.

1.35 x 103J

B.

5.38 x 103J

C.

6.72 x 103J

D.

7.06 x 103J

E.

8.06 x 103J

Correct answer is C

The formula of specific latent heat of fusion is given by: Q = mL

: 20 X 336

= 6720 or 6.72 X 10\(^3\)

1,340.

An air bubble of volume 2 cm\(^3\) is formed 20m under water. What will be its volume when it rises to just below the surface of the water if the atmospheric pressure is equivalent to a height of 10m of water?

A.

6cm3

B.

4cm3

C.

3cm3

D.

2cm3

E.

1cm3

Correct answer is A

P\(_1\)V\(_1\) = P\(_2\)V\(_2\)

When the bubble comes to the surface and pressure drops 3 times, the volume increases 3 times.

V\(_2\) = 3 x 2 

= 6 cm\(^3\)