Science Project Details:

Swimming Raisins

Difficulty: Beginner 3
Cost ($): 5
Time required:
15 minutes
Availability of materials:
Easily found
Safety concerns:

None 

Abstract

In this cool science experiment, you’ll show how to make raisins "swim" up and down in a jar, using nothing more than a few things that you commonly find in a kitchen.

Background

When baking soda is added to a vinegar solution, gas is produced and this causes hundreds of small bubbles to form. This is called a chemical “reaction”. 

This reaction between the baking soda (also known as “sodium bicarbonate”) and the vinegar (known as “acetic acid”) produces carbon dioxide gas, water, and the sodium and acetate ions which are “dissolved” in the water. 

It is this carbon dioxide gas, that causes the bubbles to form. Bubbles are little “pockets” of air or gas. As these bubbles are filled with gas, they are lighter (scientists use the term “less dense”) than the vinegar solution and will therefore float to the top of the liquid. 

An acid is a liquid that is usually sour in taste, and has a pH level of less than 7. 

Scientific Terms

Density, Chemical reaction, Sodium bicarbonate, Acid

Materials

  • 1 large glass jar (an empty peanut butter jar will do)
  • ½ a cup of vinegar
  • 2 tablespoons of baking soda
  • A handfull of raisins
  • Tap water

Procedure

  1. Fill one quarter of the jar with vinegar and top up with tap water.
  2. Stir the solution with a spoon
  3. Add the baking soda and stir
  4. Wait for a few minutes until bubbles start to form. If the bubbles don’t form, try adding more vinegar.
  5. Drop in a few raisins, one at a time, and observe. 

Observation

You will observe that the raisins sink to the bottom of the jar when they are first dropped into the jar. After a while, the raisins will rise to the top of the jar, stay there for a while, and start to sink again. 

Conclusion

The bubbles of carbon dioxide gas “stick” to the raisins and help carry the raisins up to the surface. When they reach the surface, the bubbles disappear and the raisins lose the “support” of the bubbles and sink to the bottom of the liquid, as the raisins are denser than the amount of water displaced.

Also consider

Try this experiment with different types of acids and see if it works in the same way as it does when vinegar is used. You could try lime juice, apple cider and other “sour” liquids. 

Vinegar and baking soda are often used to unclog sinks and drains, as the reaction that is produced helps to loosen up the clogged dirt. They are also used on their own, to help in household cleaning.

References

  1. http://chemistry.about.com/od/chemicalvolcanoes/ss/volcano_5.htm for the scientific formula for the chemical reaction. 
  2. http://www.ehow.com/how_4504_unclog-sink-naturally.html on “How to unclog a sink naturally”

Video(s)