Thermodynamics is the analysis of energy – particularly, how it moves and\/or changes form. The First Law of Thermodynamics is the Law of Conservation of Energy: Energy cannot be created or destroyed, but merely moves or changes form.<\/p>\n
Let’s imagine a system that has internal energy U. Then U can change only by work or heat (\u0394 means change<\/em>):<\/p>\n \u0394U = q + w,<\/p>\n q= heat, If q is negative, heat is leaving the system; if w is negative, the system is doing work against its environment.<\/p>\n The internal energy of an ideal gas is directly proportional to its temperature: specifically,<\/p>\n U = 1.5nRT, where<\/p>\n n= moles of gas present As a gas is compressed, work is done to it (so w is positive). Let’s imagine rapid compression that does not allow time for heat to escape, so q=0. Then according to<\/p>\n \u0394U = q + w,<\/p>\n U must increase. Since<\/p>\n U = 1.5nRT<\/p>\n the temperature of the (ideal) gas must rise with compression.<\/p>\n The rise of temperature during compression enables diesel engines and refrigerators to work.<\/p>\n Source:<\/p>\n Giancoli, Douglas C. Physics<\/u>, 5th ed. New Jersey: Prentice Hall, 1998.<\/p>\n
\nw=work.<\/p>\n
\nR=8.315J\/(K*mol), which is the gas constant
\nT=temperature in Kelvin<\/p>\n