 As you go down the column with non-metals, the reactivity decreases due to the decreasing electronegativity. Bromine is a liquid at room temperature. It vaporizes readily to produce a reddish-brown vapor. The vapor is denser than air. We can see this by pouring out some of the vapor and seeing it settle. As since the bromine is less reactive than chlorine, we can use a little bit more reactive metal. We'll react the bromine with some aluminum in the form of aluminum foil. The aluminum foil gives us a large amount of surface area and increases the rate of the reaction.