air is a gas. gases have various properties that we can observe with our senses, including the gas pressure p, temperature t, mass m, and volume v that contains the gas. careful, scientific observation has determined that these variables are related to one another, and the values of these properties determine the state of the gas.
if we fix any two of the properties we can determine the nature of the relationship between the other two. if the pressure and temperature are held constant, the volume of the gas depends directly on the mass, or amount of gas. this allows us to define a single additional property called the gas density r, which is the ratio of mass to volume. if the mass and temperature are held constant, the product of the pressure and volume are observed to be nearly constant for a real gas. the product of pressure and volume is exactly a constant for an ideal gas. this relationship between pressure and volume is called boyles law in honor of robert boyle who...