Question

Describe the anomalous expansion of water

Answer 1

Anomalous expansion of water is an unusual property by which it expands when cooled from 4 degree celsius to zero degree celsius.
Example:
In cold countries when the temperature drops below 0 degree celsius the surface of the pond starts radiating heat.When temperature of water falls water starts contracting  so the density increases and therefore the dense water at the surface sinks to the bottom. this continues till the temperature of the water body reaches 4 degree celsius. After four degree celsius water expands instead of contracting hence volume increases and it does not sink to the bottom. When the temperature falls below zero degree celsius the water at the top freezes while in the lower layers it remains at four degree celsius. This helps the aquatic life to survive in the cold weather.

Answer 2

$\huge{\bigstar{\underline{\green{\it{Anomalous \;expansion\; of\; water:-}}}}}$

When a given amount of water is heated from 0°C, its volume decreases and density increases until it reaches 4°C. The volume occupied by a given amount of water is lowest and its density is highest at 4°C. When the temperature is increased to 4°C the volume increases its density decreases.

Thus, when water is heated from 0°C, it contracts for 0°C to 4°C and it expands above 4°C. This phenomenon is called anomalous (or unusual) expansion of water.

Variation of volume of 1 kg of water with temperature:-

When the water is cooled below the room temperature the volume of given amount of water decreases. Until it's temperature reaches to 4°C and below 4°C, the volume increases and hence density decreases.So, it is clear said that the water has maximum density and dense the minimum volume at 4°C.

Note:

• Range of temperature at which water contracts - 0°C to 4°C.
• Temperature at which water has maximum density - At 4°C.
• The density of water at 4°C - 1000kg $m^{-3}$

Note:- Refer the above attachment for the diagram.