Describe the motion of molecules in a gas, according to the kinetic theory of gases.
Describe what is observed when viewing Brownian motion that provides evidence for your answer in (a).
At a pressure of 
and a temperature of 
, 
of helium gas has a volume of 
. The mass of of helium gas, assumed to be an ideal gas, is 
.
Calculate the root-mean-square (r.m.s.) speed of an atom of helium gas for a temperature of .
Using your answer in (i), calculate the r.m.s. speed of the atoms at 
.
