Physics
The given graph represents the cooling curve of a liquid.
(a) State the freezing temperature of the liquid.
(b) Name the phase change happening at the region QR.
(c) In which state (solid / liquid) does the above substance liberate heat at a faster rate? Justify.
Answer
(a) The freezing temperature of the liquid is 20 °C because at this temperature, the graph becomes horizontal, indicating that the temperature remains constant during the phase change.
(b) In the region QR, the phase change taking place is freezing (liquid changing into solid).
(c) The substance liberates heat at a faster rate in the solid state which is shown by the steeper slope of the graph after point R, indicating a faster decrease in temperature compared to the liquid state before point Q, where the slope is less steep.
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