One of the best know characteristics of a gas is its compressibility ...its ability to be forced into a smaller volume by the application of pressure. The first quantitative study of the compressibility of gases was carried out by Robert Boyle in 1661. He poured mercury into the end of a J-shaped tube, and noted that the volume of the enclosed gas decreased. Each addition of mercury increased the pressure on the gas, and decreased its volume. From these experiments, he formulated the law now known by his name. According to Boyle's law, the volume of a sample of gas at a given temperature varies inversely with the applied pressure. That is, V is proportional to 1/P. Thus if the pressure is doubled, the volume is halved. Boyle's law can also be stated in the following form: Pressure times volume is constant for a given amount of gas at constant temperature: To put this in mathematical form PV = constant (for a given amount of gas at a fixed temperature). Since PV = k, we can write PiVi = PfVf, where the subscript i denotes initial pressure and volume and f indicates final pressure and volume. This is the most useful form of Boyle's law for problem solving.
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