 We're going to use a small cloud chamber to demonstrate some properties of radioactivity. The cloud chamber contains a paper liner that we're going to coat with some methanol liquid. We're going to set the cloud chamber on a block of dry ice. As the dry ice cools the vapor, the container will become saturated with methanol vapor. We're going to put in a small gas heating mantle into the side. The heating mantle contains a very small amount of thorium, which is an alpha emitter. As the thorium undergoes radioactive decay and emits alpha particles, the alpha particles will leave a vapor trail through the methanol vapor. We'll shine a flashlight through the side of the cloud chamber to provide some elimination.