WAEC Physics 2021 Paper

Concept:Heating a metallic sphere without changing its state causes thermal expansion, while its mass remains unchanged.Explanation:As the temperature rises from $27^\circ\mathrm{C}$ to $200^\circ\mathrm{C}$, the particles of the metal gain more kinetic energy.This makes the metal atoms vibrate more and take up more space, so the volume of the sphere increases.The mass of the sphere does not change because no matter is added or removed during heating.Density is given by the formula $\rho = \frac{m}{V}$.Here, the mass $m$ remains constant but the volume $V$ increases.Since the denominator becomes larger while the numerator stays the same, the density $\rho$ decreases.Therefore, the result of heating is an increase in volume and a decrease in density.Answer:Its volume increases and its density decreases.Correct option: C