Came to Comment on the Laws of Physics pertaining to Gases

Jan 22, 2015
Belmont,Mass.
#1
The footballs used in the Patriots vs. Colts game were blown up inside the stadium where the temperature was probably 60-70 degrees, then they were brought out into weather that was from 33-43 degrees and left there, so they cooled down and deflated according to the laws of physics, not some hair-brained idea that the Patriot's cheated. Ask any chemist or physicist and they will tell you approximately the same thing.

"Charles’s Law (after Jacques Charles, French scientist, around 1790)

By warming the balloon up, we increase the speed of the moving gas molecules inside it. This in turn increases the rate at which the gas molecules bombard the skin of the balloon. Because the balloon’s skin is elastic, it expands upon this increased pushing from inside, and the volume taken up by the same mass of gas increases with temperature. In consequence, the density [=mass/volume] decreases with rising temperature. Cooling the balloon down again will make the balloon shrink.

Thus Charles’s law states that at a constant pressure, the volume of a given mass of gas is directly proportional to its (absolute) temperature. For two states with temperatures (T1, T2) and two corresponding volumes (V1, V2):

It must be noted that in this case (and whenever temperature appears in a multiplication or a division) the absolute or Kelvin scale must be used for temperature.

The Ideal Gas Law or Equation of State

The example used to illustrate Charles’s law probably does not follow Charles’s law exactly. It is very likely that, during the heating process, when the rate of collisions by the gas molecules increased, the pressure increased as well as the volume. Thus, in practical situations all three variables involved in Boyle’s and Charles’s law are linked and both principles are in action at the same time:

Pressure: P
Temperature: T
Density: r = m/V

These variables describe the state of the gas at any one time and are combined in the single relationship known as the ideal gas law or the equation of state:
or
where R, the constant of proportionality, is known as the universal gas constant (= 287 J·kg-1·K-1)

When mass and pressure are held constant, the gas law collapses to Charles’s law. When mass and temperature are held constant, it is equivalent to Boyle’s law. Thus, the gas law combines the two laws.

The equation of state or ideal gas law is one of the most fundamental relationships linking the three variables temperature, pressure and density that describe the thermodynamic state of the atmosphere. Some application of the gas law is involved in most practical problems in meteorology. "