Studying acids and bases can be really fun. Frequently, science experiments involve a lot of precise measuring and close instruction following. The beauty of testing for Ph with litmus strips is that you can let kids get really creative. We home school so I allowed the kids to explore our kitchen and test anything and everything. I asked the kids to hypothesis whether the liquid they were testing was an acid or base before they tested it with a Ph strip. We had a few surprises. I would recommend including ammonia, vinegar, orange juice, antacid, and bleach in your testing. If you would like to make your own Ph solution see this link.