Question

The given graph represents the cooling curve of a liquid.

1. State the freezing temperature of the liquid.
2. Name the phase change happening at the region QR.
3. In which state (solid/liquid) does the above substance liberate heat at a faster rate? Justify.

Answer 1

1. The liquid’s freezing point is 20°C, as the graph becomes horizontal at this temperature, signifying that the temperature remains constant throughout the phase transition.
2. Freezing (liquid changing into solid)
3. The substance releases heat faster in the solid state, as shown by the steeper slope of the graph after point R, indicating a greater decrease in temperature relative to the liquid state prior to point Q, when the slope is less significant.