Asked by: Don Fergusson, Shrewsbury
Water is at its densest at a temperature of approximately 4°C. If you cool it further, it begins to expand again, and once it has completely solidified into ice, it has increased in volume by about 9%. The pressure exerted by this expanding ice isn’t infinite but it is enormous. The bulk modulus of ice is around 8.8 x 109 pascals. This means that if you seal a full container of water and freeze it, the pressure on the sides of the container will be approximately 790 megapascals or 114,000 pounds per square inch. That’s 7,800 atmospheres and according to Professor Martin Chaplin of London South Bank University, the world’s leading expert on the properties of this bizarre substance, there’s no material on Earth capable of withstanding the pressures generated.