1.
Describe how you would demonstrate Brownian motion of smoke particles in the air. State and explain the observations.
Direct light into the side of an enclosed smoke cell/chamber.
View the smoke particles from the top, under a microscope.
Bright specks of smokes will be seen as light reflects from the smoke particles
The bright specks are observed to be in continuous random motion which proves that the smoke particles are in random motion.
The smoke particles are in random motion because they continually bombarded unevenly on different sides by the air molecules.
2.
*Using the kinetic model of gases, explain how gases exerts a pressure on the walls of its container.
When a gas particle collides onto the wall of the container, a force is exerted on it.
Numerous such collisions by the many molecules results in an average force exerted on the wall.
This force acting per unit area give rise to pressure exerted by the gas molecules on the walls of the container.
3.
*Using the kinetic model of gases, explain why the pressure exerted by a fixed mass of gas increases when its volume is reduced at constant temperature.
When the volume is reduced, the number of particles per unit volume increases.
Therefore, the gas particles collides more frequency with the walls, resulting in greater force exerted on the container wall.
Since pressure P = F/A, a greater force F results in greater pressure.
4.
*Using the kinetic model of gases, explain why the pressure exerted by a fixed mass of gas increases when its temperature is raised. Assume that the volume and mass of the gas remains constant.
When the temperature of the gas is raised, the particles have higher KE and moves faster.
They collide with the walls of the container more vigorously and at higher frequency, resulting in greater force exerted on the container wall.
Since pressure P = F/A, a greater force F results in greater pressure.
5.
*A gas syringe is being heated and the piston begins to be move outwards and eventually stops. Explain.
Upon heating, the gas pressure increases to more than that of the atmospheric pressure.
As a result, a resultant force acts outwards which pushes the piston outwards.
As the piston moves outwards, the volume of the cylinder increases, causing the gas pressure to decrease.
When the gas pressure drops back to a value equal to that of atmospheric pressure, there will be no more resultant outward force and the piston will stop being pushed out.