Introduction:

This can be one of the most fun experiments you do with your students, because it can have some great, dramatic results.  I have done it with just about every grade, including kindergartners.  They always have a good time with it.

Vinegar is largely acetic acid, and baking soda is a base (sodium bicarbonate).   When you mix the two of them together, they neutralize each other.   But what makes this reaction so neat is that as the bicarbonate breaks apart bubbles galore release.  Now, you may have seen this yourself before, when someone pours vinegar into a glass with baking soda at the bottom of it.   Neat, but let’s make it more dramatic for your students.  Follow the directions below.

Materials:

• A 20 oz. soda pop bottle, empty
• A balloon
• A few ounces of vinegar
• A funnel (for pouring vinegar into the bottle)
• Enough baking soda to half fill the empty balloon.

Experimental Details:

These directions are aimed at one teacher performing the experiment as a demonstration in front of her or his students.  It can easily be done by two students, one holding the bottle and one using the balloon.

1. Stretch out your balloon several times to that it isn’t stiff.
2. Pour the vinegar into the empty soda pop bottle.
3. Fill your empty balloon about half full of baking soda.
4. Snap the balloon tightly around the neck of the bottle, leaving the baking soda in the balloon so that it is flopped over the side.
5. Raise the balloon up so that the baking soda pours into the vinegar.
6. Shake the bottle gently to mix, if necessary.
7. Observe.

Expected Results:

The balloon will blow up, rapidly at first, then more slowly as the mixing is completed.  The gentle swirling is suggested simply to help the two ingredients mix evenly and completely.

On occasion, someone knocks over a bottle.  If the balloon is already snapped on the bottle neck, that’s no problem.  As long as the two ingredients mix, the reaction will run.

Safety Precautions:

It’s hard even to conceive of any safety problems here. The vinegar is edible, though probably disgusting to taste. Baking soda is still used as the poor man’s whitening toothpaste, so it is rather harmless.

I supposed someone could get either of these in their eyes, which would be dangerous. I have never had any such problems, even with kindergarten classes. Nevertheless, it’s worth mentioning.

Teacher Tips:

I mention stretching the balloon out before putting the baking soda in it.   We are all probably familiar with how a balloon can be difficult to blow up when taken from its bag, but easier to blow up when it’s been stretched out a bit.  The same goes true for this experiment.   Make sure the balloon opening stretches around the bottle top before putting any baking soda in it.

Variations:

As I have already mentioned, this experiment is one that can be performed with kindergartners because of its ease and simplicity. The younger children are just learning a bit about how changing the conditions might change the outcome in just about any situation. In this experiment, you can have them change the amount of baking soda they add. They can add more, but use the same amount of vinegar and see if the balloon blows up bigger. They can add less while keeping the amount of vinegar unchanged and see if that affects the balloon’s size. The same approach can be taken with the vinegar—change the amount you add while keeping the baking soda unchanged.

Keep in mind that if you try this variation with your students that you will need several gallons of vinegar and several boxes of baking soda.

Source:

Inexpensive, Easy Science Experiments for Grade Schoolers
By Mark A. Benvenuto
Copyright@2002, Mark A. Benvenuto
Published by Mark A. Benvenuto
University of Detroit Mercy
Department of Chemistry and Biochemistry
4001 W. McNichols Rd.
Detroit, MI 48219-0900

Suggested for inclusion in this CD by Marsha Phillips, Chicago Section