Pour each liquid into the glass slowly starting with the sugar syrup ( add food colouring if you want ), followed by the water with added food colouring and finally the vegetable oil.
Drop a few small items in and see which layer they float on.
Do you know why they float on different layers?
Try a marble to see if it sinks to the bottom.
The science part
For a full explanation see this post.
We’d love to see your Christmas themed density jars.
Original article and pictures take http://www.science-sparks.com/2014/12/20/christmas-density-display/ site