Posted By Paul Leadbetter Julie When air expands, it cools down; if it cools enough, you may get condensation of any water vapour. If there is further cooling, the condensed water can freeze. The opposite effect can be experienced when using a bicycle pump; when air is compressed, it gets hot. Paul

Posted By Stuart Nagle In 1848 Thomson produced a paper which set out to establish the basis of an absolute thermometric scale. He resolved that this scale could be produced when each degree was determined by the performance of equal quantities of work in causing one unit of heat to be transformed while being let down through that difference of temperature. This indicated as the absolute zero of temperature the point that would be marked as -273 degrees on an air thermometer scale. Thomson continued his research, experimenting on the heat developed by compression of air and verifying the prediction of his brother, Professor James Thomson, regarding the reduction of the melting point of ice by means of pressure. He gave a thermodynamic explanation of the non-scalding property of steam issuing from a high-pressure boiler. Between 1851 and 1854 he formulated the two great laws of thermodynamics, the laws of equivalence and of transformation. In collaboration with Joule, he laid the foundations of thermodynamics in a series of papers, Thermal Effects of Fluids in Motion.