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What Are The Consequences Of Expansion Of Water?

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sampreeti  baruah Profile
Anomalous expansion of Water:
Generally, all liquids expand due to heating. But water behaves in a peculiar way when heated from 0oC to 4oC. On heating from 0oC up to 4oC its volume decreases, reaches a minimum at 4oC such that the density of water is maximum at 4oC on heating further, water behaves like any other liquid. Similarly, during cooling process, the volume of water decreases up to 4oC, reaches a minimum at 4oC, if further cooled up to 0o C, its volume increases instead of decreasing and hence, density of water at 0oC is lesser than that at 4oC. Water freezes to ice at 0oC. Being less dense than water, ice floats on water. Beyond 4oC, water behaves like any other liquid.
This unique feature of water between 0 and 40C, is a boon to aquatic animals. Let us see how-
In cold countries and Polar Regions during winter, the temperature goes below 00C. In lakes and ponds when water at the surface reaches 40C, it is densest and goes to the bottom. When the temperature further reduces, only surface layers of water freeze whereas at the bottom water remains at 40C. Aquatic animals live comfortably in water at 40C ,whereas, outside temperatures may go much less than that.
sampreeti  baruah Profile
Normally, liquids contract on cooling & become more dense. However, water contracts when cooled to a temperature of 4oC and thereafter expands as it is cooled further from 4oC to 0oC. Water attains its maximum density at 4oC. This phenomenon is useful for the preservation of marine life in very cold temperatures. Initially, the surface water in water bodies starts cooling. Upon reaching the temperature of 4oC, the surface water descends to the bottom as it denser. Upon further cooling between 4-0 degrees C, a temperature gradient is set up in depths of the water body whereby, the bottom-most layer is at 4 deg C & the temperature gradually drops as one goes upwards. At 0 deg C, ice is formed. Ice being lighter than water, floats to the upper surface. Further, water and ice are bad conductors of heat. All this help in the maintenance of temperature of the water at the bottom at 4 deg C. It is in this layer that marine life is able to sustain itself.

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