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WAEC Physics 2014 Paper

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Question : 22

Total: 48

The mass of an empty density bottle is 30g. When filled with a liquid, the mass of the bottle and the liquid is 40g. On heating the filled bottle through 40ºc, the mass reduces to 38g. Calculate the apparent cubic expansivity of the liquid

6.25 x 10K^-1
6.25 x 10^-3K^-1
2.50 x 10^-3K^-1
2.50 x 10^-4K^-1

Solution:

Concept:

Apparent cubic expansivity measures the volume expansion of a liquid relative to the container, using the mass of liquid expelled and the mass of liquid remaining.

Explanation:

Mass of empty bottle =

30\,g

Mass of bottle + liquid =

40\,g

Mass of liquid initially =

40 - 30 = 10\,g

After heating through

40^\circ C

, mass of bottle + remaining liquid =

38\,g

Mass of liquid remaining =

38 - 30 = 8\,g

Mass of liquid expelled =

10 - 8 = 2\,g

Apparent cubic expansivity formula:

\text{Apparent cubic expansivity} = \frac{\text{mass expelled}}{\text{mass of liquid left} \times \text{temperature rise}}

\Rightarrow \frac{2}{8 \times 40} = \frac{2}{320} = 0.00625\,K^{-1}

= 6.25 \times 10^{-3}\,K^{-1}

Answer:

B.

6.25 \times 10^{-3}\,K^{-1}

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