Anomalous behaviour of water in lakes
Normally, liquids contract on cooling & the density increases. However, water is special. It contracts when cooled, down to a temperature of 4°C but thereafter begins to expands as it reaches 0°C and turns into ice.
Water attains its maximum density at 4°C. This is caused by the hydrogen bonding between the oxygen atoms that are negatively charged and the hydrogen atoms that are positively charged, from two different molecules of water. The density of ice is lower, and so it floats on water. This anomalous expansion of water is an abnormal property of water whereby it expands instead of contracting when the temperature goes from 4°C to 0°C, and it becomes less dense. The density becomes less as it freezes because molecules of water normally form open crystal structures when in solid form. Water is denser than ice while almost all the other substances are denser in solid form than in liquid form.
This phenomenon is useful for the preservation of marine life in very cold temperatures. During winter, the surface water in water lakes and rivers starts cooling. Upon reaching the temperature of 4°C, the surface water descends to the bottom as it denser. Upon further cooling to freezing point, a temperature gradient is set up in depths of the water body whereby, the bottom-most layer is at 4°C and the temperature gradually drops towards the surface where it is ice. . Further, water and ice are not good conductors of heat. All this help in the maintenance of temperature of the water at the bottom at 4°C. It is in this layer that marine life is able to sustain itself. Had water been like any other liquid, the whole depth of the water would have been frozen and aquatic life would have been destroyed completely.
Normally, liquids contract on cooling & the density increases. However, water is special. It contracts when cooled, down to a temperature of 4°C but thereafter begins to expands as it reaches 0°C and turns into ice.
Water attains its maximum density at 4°C. This is caused by the hydrogen bonding between the oxygen atoms that are negatively charged and the hydrogen atoms that are positively charged, from two different molecules of water. The density of ice is lower, and so it floats on water. This anomalous expansion of water is an abnormal property of water whereby it expands instead of contracting when the temperature goes from 4°C to 0°C, and it becomes less dense. The density becomes less as it freezes because molecules of water normally form open crystal structures when in solid form. Water is denser than ice while almost all the other substances are denser in solid form than in liquid form.
This phenomenon is useful for the preservation of marine life in very cold temperatures. During winter, the surface water in water lakes and rivers starts cooling. Upon reaching the temperature of 4°C, the surface water descends to the bottom as it denser. Upon further cooling to freezing point, a temperature gradient is set up in depths of the water body whereby, the bottom-most layer is at 4°C and the temperature gradually drops towards the surface where it is ice. . Further, water and ice are not good conductors of heat. All this help in the maintenance of temperature of the water at the bottom at 4°C. It is in this layer that marine life is able to sustain itself. Had water been like any other liquid, the whole depth of the water would have been frozen and aquatic life would have been destroyed completely.
