Ludwig Eduard Boltzmann (1844 – 1906)
Boltzmann argued that
The physical properties of gases may be explained by the model of fast moving molecules in a large empty space
Even in 1900 this view was disputed by many philosophers and scientists! Strongly depressed Boltzmann committed suicide in 1906.
This video comes from → puku0987
Example: $1 mol= 6,023\cdot 10^{-23}$ atoms of helium have SNTP a volume of $22,4\;dm^{3}$ So to $1\; atom \; He$ corresponds a cubic volume of $\frac{22,4\cdot 10^{-3}}{6,023\cdot 10^{23}}m^3\approx 3,7\cdot 10^{-26}m^3$ We can therefore consider that from the center of this atom to the center of the nearest atom there is an average distance of $ (3,72\cdot 10^{-26})^{\frac{1}{3}}=1,5\cdot 10^{-7} m$ Now $1 \; atom\; He$ has a diameter of $0,1 nm= 10^{-10}m$ These two distances are in an approximate ratio of $\frac{1,5\cdot 10^{-7}}{10^{-10}}\approx 1500 $ Therefore, it is unlikely that helium atoms meet each other, even if they move very quickly! In general:
An ideal gas is a gas whose molecules have no mutual interaction. These molecules can be treated as material points.
If the number of molecules per unit volume increases (for example due to a pressure increase and a volume contraction) or if their diameter increases we may well deviate from the ideal conditions!
The movement of molecules is random. It is therefore subject to the laws of statistics
Thus, if a gas molecule of mass $m$ undergoes a velocity change $\Delta \vec{v}$ in a time $\Delta t$, we can say that it was exposed to an average force $\vec{F}$ in the same direction and sense as the vector $\Delta\vec{v}$, given by
Average force: $\vec{F}=m\frac{\Delta \vec{v}}{\Delta t}$ where: $\Delta \vec{v}$ is the velocity change $\Delta t$ is the time of this change
Since there is no interaction between molecules of the ideal gas, these molecules are subject to (or perform) no force as long as they move freely within the volume they occupy. Their speed remains constant. However, if they hit the wall of their container, their speed changes and they are subject to a force! Newton's law of action and reaction shows that the wall must be subject to an opposing force and therefore a pressure! This is called the gas pressure!