Water has maximum density at 4`C.Why is it so?Why does water expand anomalously? I know the phenomenon ,but,please explain that why it happens. Also,why it happens only in water.

Asked by arymahajan24 | 28th Aug, 2016, 12:42: PM

Expert Answer:

The mass of any substance undergoing expansion while heating remains the same. But its volume however increases. Thus, its density decreases.
In liquids and gases, the volume increases by an appreciable amount on heating and therefore the density decreases considerably. But on the contrary water exhibits an anamolous expansion on cooling and contraction on cooling  within a specific range of temperature.
When water at 0°C is heated, it is observed that it contracts between 0°C and 4°C, ie.volume decreases and thus density increases .The volume of water is minimum at 4°C. Hence we say that the density of water is maximum at 4°C. Beyond 4°C, it expands normally. i.e density decreases. And thus we get that the density of water will be minimum at 100°C.
On plotting density of water along y-axis and temperature along x-axis, we get a graph as shown below. The value of temperature corresponding to the value of the density on y axis gives the temperature at which the density of water gives the particular value.
At high temperature the density of water is minimum as water expands on heating after 4 °C.

Answered by Vaibhav Chavan | 30th Aug, 2016, 05:58: PM

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