Make an Acid-Base Rainbow Wand

Here's an easy and colorful chemistry demonstration for you. Take a long glass tube and fill it with Universal Indicator solution. Add a few drops of 0.02M HCl to one end of the tube and seal it with a stopper. Add a couple of drops of 0.02M NaOH to the other end of the tube and seal it. The Universal Indicator will respond to the pH gradient by providing you with a lovely rainbow. You can invert the tube a few times to speed things up.

You can get a similar result using home chemistry. Fill a clear straw with red cabbage juice. Add a little lemon juice or vinegar to one end of the straw. Add a few drops of baking soda or laundry detergent solution to the other end of the straw.