Assertion (A): Water will freeze at a higher temperature if the pressu...
Assertion (A): Water will freeze at a higher temperature if the pressure is increased.
Reason (R): Water expands on freezing which by Clapeyron's equation gives a negative slope for the melting curve.
The correct answer is option 'A', which means that both the assertion and the reason are individually true, and the reason is the correct explanation of the assertion.
Explanation:
Assertion (A): Water will freeze at a higher temperature if the pressure is increased.
When the pressure is increased, the freezing point of water also increases. This can be observed in everyday life, for example, when salt is added to icy roads to lower the freezing point of water and prevent it from freezing at lower temperatures.
Reason (R): Water expands on freezing which by Clapeyron's equation gives a negative slope for the melting curve.
Clapeyron's equation relates the pressure and temperature at which a substance undergoes a phase change, such as melting or freezing. For a substance that expands upon freezing, the slope of the melting curve on a pressure-temperature diagram is negative.
When water freezes, it undergoes a phase change from a liquid to a solid. Unlike most substances, water expands upon freezing. This expansion is due to the unique arrangement of water molecules in the solid state, which forms a crystalline structure with open spaces between the molecules. As a result, the density of ice is lower than that of liquid water.
Explanation of the Correct Answer:
The correct answer is option 'A', which states that both the assertion and the reason are true, and the reason is the correct explanation of the assertion.
The freezing point of water is influenced by pressure. When the pressure is increased, the freezing point also increases. This can be explained by Clapeyron's equation, which gives a negative slope for the melting curve when a substance expands upon freezing. Since water expands on freezing, the slope of its melting curve is negative.
Therefore, the reason provided in statement (R) correctly explains why water will freeze at a higher temperature if the pressure is increased.
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