The densities of different liquids can be easily demonstrated by making a density column. Steve Spangler has a splendid density column demo that I decided to make on a much larger scale. Instead of using a graduated cylinder I decided to use a fluorescent light bulb tube guard. To seal one end of the tube I used duct tape and Goop so that no liquid would leak out. Once the tube is ready, it's just a a simple matter of pouring the liquids into the tube according to their densities. Check out the video for the results and for some additional tips.
References allow you to track sources for this article, as well as articles that were written in response to this article.