making suds

This is a fun outdoor activity for kids and a science experiment all in one.

Materials needed:
Tall plastic cup or any other tall container
liquid dish detergent
1/2  cup warm water
1 tsp. Baking soda
Citric acid
Measuring cups

1. Mix three big squirts of the liquid dish detergent, 1/2 cup warm water, and one teaspoon of baking soda in the plastic container.  
2.  Sprinkle in couple pinches of the citric acid into the solution.  
3.  Watch the suds form.

note:  I bought my citric acid from amazon.com.  It's a rather large bag of it, but I do use it when I am making my own dishwasher detergent.

To integrate this into a science experiment discuss with the children what a base and an acid is.  The suds occur because the baking soda is a base and when you add the acid (citric acid), it produces carbonic acid.  The carbonic acid breaks down the water and carbon dioxide as a gas and the gas launches the bubbles.  Can you think of other household acid and bases?