school projects

Floating and Sinking



Watch items sink to the bottom, and then float back up. Some even seem to dance!

Materials
clear plastic or glass container, water, vinegar, baking soda, food coloring, items

Directions

jug

Fill the container with 3 parts water and one part vinegar. Be sure to leave some room at the top of the container.

Slowly add one teaspoon of baking soda, very slowly! Too much at one time and it will all bubble over the top. Have a towel handy if the kids are adding the baking soda!

When the bubbles settle down, slowly add a second teaspoon of baking soda.

When the bubbles settle, add a few drops of food coloring. Notice the the liquid is moving and quickly mixes in the color.

Now comes the fun part. Find some interesting items (raisons, rice, dried fruit or vegetables, broken bits of spaghetti, pieces of fruit - grapes cut in half). Will the items float or sink?

Drop in a few of the first item. Usually they will sink to the bottom. Wait a few minutes and then they will rise to the surface, then sink again. Rice almost seemed to dance.

It is fun to watch for hours and just observe how different items react. If the movement seems to be slowing 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. When enough bubbles attach to the object, it floats to the surface and releases the gas. Then it sinks back to the bottom to start the process again.




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