WAEC Physics 2020 Paper

Concept:Heat flows between the water and the room until the water reaches the surrounding room temperature of $25^\circ C$.Explanation:The cup at $45^\circ C$ is hotter than the room, so it loses heat to the surroundings and gradually cools down.The cup at $5^\circ C$ is cooler than the room, so it gains heat from the surroundings and gradually warms up.Both cups move toward the room temperature of $25^\circ C$.The rate of temperature change depends on the temperature difference between the water and the room.As this difference decreases, cooling or heating becomes slower.Therefore, each temperature change is shown by a smooth curve, not a straight line, approaching $25^\circ C$.Answer:The correct graph is the one showing a curve falling from $45^\circ C$ and a curve rising from $5^\circ C$, both gradually approaching $25^\circ C$.