Dec 1989 P2 Q8a, 8b(i)
(a) A sealed flask contains a gas.
(i) Describe the motion of the gas molecules
(ii) Explain how the motion of the gas molecules results in a pressure exerted by the gas on the walls of the flask.
(b) Explain what is meant by Brownian motion.
*************************
Answer:
(a)
(i) The gas molecules move at a high speed in random directions.
(ii) The moving molecules bombard all parts of the wall of the flask. This bombardment causes a force on the wall, and hence a pressure on the wall. The pressure of the gas is dependent on the frequency of collisions and the speed of the molecules.
(b) Brownian motion is the random movement of light particles within a fluid. An example is smoke particles in air.
