We did a fun experiment today using Bromothymol Blue (BTB), which is a chemical that changes color when exposed to acids or bases. I purchased it on Amazon.com from a chemical supplier pretty inexpensively, and you only need to use a little – just put a small amount in a cup and add water.
To set up the experiment, I set out several clear plastic cups and got out our various supplies. I filled the cups half full with the BTB / water mixture and then let the kids take turns adding things to see what would happen. The older kids created a table to document the results.
Here are the things we added to it and the results:
Baking soda: stayed blue
Effervescent tablet (we used generic denture cleaner): bubbles turned yellow, then once they were gone it was blue
Vinegar: turned yellow
Vinegar and baking soda: lots of bubbles, in fact bubbled over – use a tray! And, it turned yellow and felt cold.
You can also add Calcium Chloride (CaCl2) - sold as ice melt, but you need straight CaCl2 and we could only find a blend! It won’t change the color but will make the cup feel cold. If you combine CaCl2 and baking soda you’ll get milky yellow bubbles.
Post a comment if you find anything else fun to add!