Anomalous expansion of water : Generally any material expands on heating and contracts on cooling. But in case of water, it expands on heating if its temperature is greater than 4°C. In the range 0°C to 4°C, water contracts on heating and expands on cooling, i.e. is negative. So water have this special property, which is not found in any existing natural material. This behaviour of water in the range from 0°C to 4°C is called anomalous expansion.