To understand and visualize the movement of molecules in a gas.
- A wire mesh cage, a bird cage will do.
- Some ping-pong balls.
- A few different colors of paint.
- A blow dryer.
- A paintbrush.
- Suspend the cage from the ceiling by a wire or rope.
- Paint the ping-pong balls in different colors and put them in the cage after drying. Make sure you close the cage.
- Hold the hair dryer under the cage and switch it on at low heat setting. Observe the movement of the balls flying around.
- Increase the heat settings of the blow dryer. Observe how the movement of the balls increase.
- Observe how the painted balls move around randomly and collide with each other. This is exactly how molecules move and collide in a gas.
All kinds of matter we see around us are made up of molecules. Not only solids and liquids, even gases are made up of molecules, even though they are not visible to our eye as they are less densely packed than in solids and liquids. Molecules are free to move around in a gas and move around randomly colliding with each other all the time. As the temperature of the gas increases, the energy of the molecules increase and their speed increases, hence leading to more random movement and collisions. In this experiment the air from the blow dryer simulate the behaviour of molecules of gas. As the temperature of the blow dryer increases, the balls move faster.