Test Index

WAEC Physics 2021 Paper

Question : 40

Total: 50

Solution:

Concept:

The energy required to change the temperature of a substance without changing its state is given by the heat formula

Q = mc\Delta\theta

Explanation:

Here, the ice is initially at

-5^\circ

C (below the freezing point) and is heated to

0^\circ

Given:

m = 20\ \mathrm{g}

c = 2.1\ \mathrm{J/g^\circ C}

Temperature change:

\Delta\theta = 0 - (-5) = 5^\circ\mathrm{C}

Substitute into the formula:

Q = mc\Delta\theta = 20 \times 2.1 \times 5

Q = 210\ \mathrm{J}

Answer:

The energy required is

210\ \mathrm{J}

Correct option: D. 210 J.

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