Vinegar
Vinegar is a great item to have on hand - it's a key component in many simple and safe chemical reactions
Seashells and Acidification
Egg-speriment
Steel Wool and Vinegar
Salt, Vinegar and Pennies
The Importance of Brushing Your Teeth
Baby Birds and Acid Rain
Why You Need Calcium
From Solid and Liquid to Gas
Erupt a Volcano
The Cabbage Caper
Mystery Solutions Lab
pH of Household Substances
Comment on this post to be entered to win a prize box containing most of the Top Ten Items. And remember, if your comment contains an additional use (not mentioned above) for vinegar in the science classroom, you'll receive a bonus entry!
By the way, vinegar won't be included in the prize box - can't figure out how to ship that easily. Guess I'll have to find a special surprise item to take its place!