Knowing what information would allow you to order gas molecules according to their velocity?
A. Pressure and temperature
B. Volume and molecular mass
C. Pressure and volume
D. Temperature and molecular mass
D. Temp gives you KE, and KE, knowing mass, gives you velocity
To order gas molecules according to their velocity, you need to consider the factors that affect the kinetic energy of the gas molecules. The kinetic energy of a gas molecule is directly proportional to its velocity.
The formula for the average kinetic energy of gas molecules is:
KE = (3/2) * k * T
Where:
KE = kinetic energy of the gas molecules
k = Boltzmann constant
T = temperature
From this formula, it is clear that the velocity of gas molecules is dependent on temperature. Therefore, the factor that is necessary to order gas molecules by their velocity is the temperature. This eliminates options B and D, as they do not include temperature.
On the other hand, pressure and volume are related to the number of gas molecules and their density, but they do not directly affect the velocity of individual gas molecules. Thus, option C can be eliminated.
Therefore, the correct answer is option A: Pressure and temperature.