Diffusion

This is a wonderful experiment to show how to gasses ( HCl - acidic, NH3 - alkaline) can diffuse towards each other and react to form an additive compound NH4Cl which forms the fume inside the tube.
This hardly takes a few minute and we can visibly see the reaction happening where two gasses mixes together to form white fume of NH4Cl and get deposited .
Although to get a tube where both side is open may not be easy , but I am sure , your school supplier can get one for this experiment.
Thanks .