Here is an easy, inexpensive and fun kid experiment for your next kid birthday party.

This activity, which is strictly speaking a kid science experiment, can be used in any party as entertainment. Even better: have a "Mad Chemist" theme and use this idea as one of the kid experiments.

Fill a plate or saucer with milk and put in a few drops of food coloring on top of the milk in different spots. The smaller the drops the better.

Use a spoon to pour a small amount of dishwashing liquid into the milk. Pouring it into the center works best.

Now watch the colors dance and explode.

This might sound very simple to you, but I've done this a few times with kids aged 6 - 10 and was amazed at how much pleasure this gave them! Let them each do their own - provide different colors and encourage them to try out different things. You will be amazed at the beautiful patterns they manage to create. Allow them to repeat the process a few times. They'll get the hang of it after one or two tries. If the kids are too small to do it themselves, you can do it as a demonstration. Or, why not just let them bring old clothes with, put down lots of old newspapers and allow them to make a big mess. They will love you for it!

Explanation:
Water has a "skin" called surface tension. This is a force on the surface of water which pulls it inwards. Soap or dishwashing liquid breaks down the surface tension and stops the skin from forming. This stops water sticking together in drops and so it flows more easily into all the places where dirt collects.