At which temperature does liquid water show maximum density ?

[amp_mcq option1=”299 K” option2=”277 K” option3=”285 K” option4=”373 K” correct=”option2″]

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UPSC NDA-2 – 2024

Liquid water exhibits its maximum density at 4°C. Converting this to Kelvin, we get 4 + 273.15 = 277.15 K. The option closest to this value is 277 K.

– Unlike most substances which become denser as they are cooled, water behaves unusually in the temperature range of 0°C to 4°C.
– As liquid water cools from higher temperatures, its density increases until it reaches a maximum density at approximately 4°C (3.98°C to be precise).
– Below 4°C, the density of liquid water starts to decrease as it approaches its freezing point (0°C). When it freezes to form ice at 0°C, its density decreases significantly, which is why ice floats on water.
– This anomalous expansion of water is crucial for aquatic life in cold climates, as the densest water (at 4°C) sinks to the bottom of lakes, allowing life to survive below the surface ice.

The Kelvin scale is an absolute thermodynamic temperature scale where 0 K is absolute zero. The relationship between Celsius (°C) and Kelvin (K) is K = °C + 273.15. The boiling point of water at standard atmospheric pressure is 100°C or 373.15 K.

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