Definition and Physical Significance
The compressibility factor is defined as
where is the molar volume, is the molar volume of the corresponding ideal gas, is the pressure, is the temperature, and is the gas constant. For engineering applications, it is frequently expressed as
where is the density of the gas and is the specific gas constant, being the molar mass.
For an ideal gas the compressibility factor is per definition. In many real world applications requirements for accuracy demand that deviations from ideal gas behaviour, i.e., real gas behaviour, is taken into account. The value of generally increases with pressure and decreases with temperature. At high pressures molecules are colliding more often. This allows repulsive forces between molecules to have a noticeable effect, making the molar volume of the real gas greater than the molar volume of the corresponding ideal gas, which causes to exceed one. When pressures are lower, the molecules are free to move. In this case attractive forces dominate, making . The closer the gas is to its critical point or its boiling point, the more deviates from the ideal case.
Read more about this topic: Compressibility Factor
Famous quotes containing the words definition, physical and/or significance:
“Mothers often are too easily intimidated by their children’s negative reactions...When the child cries or is unhappy, the mother reads this as meaning that she is a failure. This is why it is so important for a mother to know...that the process of growing up involves by definition things that her child is not going to like. Her job is not to create a bed of roses, but to help him learn how to pick his way through the thorns.”
—Elaine Heffner (20th century)
“The vast material displacements the machine has made in our physical environment are perhaps in the long run less important than its spiritual contributions to our culture.”
—Lewis Mumford (1895–1990)
“For a parent, it’s hard to recognize the significance of your work when you’re immersed in the mundane details. Few of us, as we run the bath water or spread the peanut butter on the bread, proclaim proudly, “I’m making my contribution to the future of the planet.” But with the exception of global hunger, few jobs in the world of paychecks and promotions compare in significance to the job of parent.”
—Joyce Maynard (20th century)