Demo Ideas

Title: Floating and Sinking Experiments
Source: http://www.sciencekidsathome.com
Target age: kindergarten scientists
Materials: Clear plastic or glass container, water, baking soda, food coloring, rice and raisons and any other small pieces of food items
Prep Time: less than 5 mins
Demo Time: 5 minutes or more

Description: Almost fill container with 3 parts water and one part viegar. Leave room at the top of the container.
Slowly add one teaspoon of baking soda very slowly, adding too much at one time will make it bubble over the top. When the bubbles settle down, slowly add another teaspoon of baking soda. When the bubbles settle, add a few drops of food coloring. notice the liquid is moving and quickly mixes in color. Now comes the fun part! Will the items float or sink? Drop in a few of the first item. usually they will sink to the bottom. Wait a few mins and they will rise to the surface, then sink again. Rice almost seem to dance! The itmes can be watched for hours. If movement seems to slow down, add another teaspoon of baking soda.

What is Happening?

The vinegar is an acid and the baking soda is a base. When you combine them, a chemical reaction produces carbon dioxide. The carbon dioxide bubbles build up on the surface of the object, it floats to the surface and releases the gas. Then it sinks back to the bottom to start the process again.