Anomaly of Water

Most matter in state will expand when it is heated. Because it molecular element move faster and need more space. And so does water, it has the same character. Cold water is heavier than warm water, which is why it sinks to the bottom in a container. But whyice cube drift on the surface of a glass of water? Why is it then that the water on the surface of a lake freezes first?

Most matter expands when heated and shrinks again when it cools. But water does not always behave in this normal way, only at temperatures of between its boiling point (100°C) and four degrees Celsius. Below four degrees, or, to put it more exactly, between freezing point (0°C) and four degrees, water expands again when it cools.

This is because it has a higher density at four degrees Celsius than at lower temperatures. And this in turn means that when it cools down to four degrees it becomes increasingly heavy but if it cools down further, up to zero degrees, it becomes lighter again.

And now, when the surface layer of a lake cools down in winter, this water sinks down into the depths. Warmer water rises up and subsequently cools down, too. Colder and warmer water now keep shifting around until the temperature throughout the lake has reached four degrees Celsius. If the water on the surface now cools down even further, it becomes lighter and does not sink down.

At zero degrees Celsius it freezes into ice, whereas the water on the bottom of the lake is still at four degrees. The way that water only shrinks until it reaches a temperature of four degrees Celsius and expands again if it cools down further is known as the anomaly of water and is the reason why it can be warmer at the bottom of a lake than on its surface.

Many animals cannot survive at freezing point, they can attacted by hypoterm or freezed instead. But much of them can still alive at water in four degrees. This anomaly of water is very beneficial for animal that live in deep lake or sea, that the temperatute can less than freezing point.

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