(a)[2]
Describe, in terms of the kinetic theory of gases, how molecules move in a gas.
(b)[2]
Describe what is seen when Brownian motion is viewed, as this gives evidence for your answer in (a).
(c(i))[3]
At a pressure of $1.05 \times 10^{5}\,\text{Pa}$ and a temperature of $27^{\circ}\text{C}$, $1.00\,\text{mol}$ of helium gas has a volume of $0.0240\,\text{m}^3$. The mass of $1.00\,\text{mol}$ of helium gas, treated as an ideal gas, is $4.00\,\text{g}$. Calculate the root-mean-square (r.m.s.) speed of a helium atom for a temperature of $27^{\circ}\text{C}$.
(c(ii))[3]
Using your answer in (i), calculate the r.m.s. speed of the atoms at $177^{\circ}\text{C}$.