From the equation for Z from this website https://books.google.com.sg/books?i...page&q=collision frequency Z equation&f=false It shows that as T increases Z decreases. However this seems quite counter intuitive to me as I had always been taught that as temperature increases so does the frequency of effective collisions/collisions. The only reason that I could think of was due to the mean free path increasing as temperature increases causing the frequency of collision to decrease. But I feel that a problem with that statement is that even though the mean free path increases, the velocity of the gas increases so wouldn't that cancel out the effect of having a greater distance to cover? So why does an increase in T decrease Z? Secondly, in the equation for Z the average speed of the molecules, c is in the numerator of the equation while temperature, T is in the denominator. This again seems weird to me because I always thought that the speed of molecules and temperature should be proportional to each other so they shouldn't be on opposite sides of the fraction. Why aren't they both on one side of the equation?