Your friend smells cinnamon coming from an inflated rubber balloon containing cinnamon extract. You tell him that the cinnamon molecules are passing through the micropores of the balloon. He accepts the idea that the balloon contains micropores but insists that he is simply smelling cinnamon-flavored air. You explain that scientists have discovered that gases are made of molecules, but that’s not good enough for him. He needs to see the evidence for himself. How might you lead him to accept the concept of molecules?