Water is the liquid that initially contracts when cooled down to 4°C but on further cooling down to 0° C, it expands. Generally, the volume of substances increases on heating and decreases on cooling. But when water is heated from 0 degree Celsius to 4 degree Celsius, its volume decreases and increases only after 4 degree Celsius. This unusual behavior of water from 0 degree Celsius to 4 degree Celsius is known as anomalous expansion of water. As density is inversely proportional to volume, so, density of water increases from 0 degree Celsius to 4 degree Celsius. At 4 degree Celsius, water has minimum volume and maximum density.