Which of the following statements about water is NOT correct?

Analyze the question: We need the statement that is NOT correct about water. This tests the anomalous expansion of water.

Concept: Water behaves unusually between 0°C and 4°C. As it cools from a higher temperature, it contracts until it reaches 4°C, where it has its minimum volume and maximum density (about 1000 kg/m³). Below 4°C, it expands again until it freezes at 0°C. Ice is less dense than water, which is why ice floats.

Check each option:

• A. Pure water freezes at 0°C under normal (standard) pressure. Correct.
• B. "The volume of a given mass of water at 0° is less than its volume at 4°C." Since the volume is smallest at 4°C, the volume at 0°C is greater than at 4°C. So this statement is false, which makes it the answer.
• C. Water boils at a definite temperature (100°C at standard pressure). Correct.
• D. Evaporation occurs at all temperatures, because faster molecules at the surface can always escape. Correct.
• E. Water has maximum density at 4°C. Correct.

Answer: The statement that is NOT correct is B.

Exam tip: Remember "4°C = smallest volume, biggest density." Any option that says water at 0°C has a smaller volume than at 4°C is a trap. Also remember that boiling occurs at a definite temperature, while evaporation occurs at any temperature.