In our chemistry textbook, the little kids and I were just learning about the pH scale, so on Monday (which I guess was technically a holiday) we made our own pH indicator juice from red cabbage (and it was totally okay that we spent the morning doing schoolwork because the kids spent about six hours outside in the afternoon so it's not like they didn't enjoy their "vacation" day).
One set of instructions said to soak the cabbage in boiling water. The other said to use cold water (I think to keep it very kid-friendly and completely risk-free). We tried both ways and found that the hot water was a lot more effective (and talked about why this would be the case—what with all those molecules bouncing around energetically). Here's Miriam and Benjamin mashing the cabbage leaves:
Once that part was finished, we just went about the house collecting liquids and powders to test—vinegar, lemon juice, milk (cow), milk (almond), mouthwash, glass cleaner, baking soda, cream of tartar, and sea salt were among things that we tested. Also hand soap and dish soap. Also bleach, which the instructions said explicitly not to experiment with...which only made Rachel want to experiment with it more (and since we knew cabbage water was neutral we really didn't see the harm in adding a couple drops of bleach (I think the "danger" here was the bleach itself, not mixing it with the cabbage water)).
We just added all of our liquids and arranged them around our purple-neutral cabbage water:
Acids turned pink, bases turned blue...or green...or yellow...depending on how basic they were. Bleach turned things yellow pretty quick. Glass cleaner turned bright green. The blues were the baking soda and...surprisingly...almond milk (which seems to "swing" basic as well, which I didn't know...but which I guess makes sense because a lot of nuts are somewhat bitter).
The strong acids were equally interesting to watch change color, switching from purple to pink right before our eyes. Hand soap surprised us by being pink (it's the pastel pink, second from the left in this picture, but it's only pastel because of all the foamy bubbles at the top—underneath it's a pretty bright pink), while dish soap was somewhat basic.
When we had finished with the experiment we were about ready for lunch. I made a quick ramen noodle cabbage salad (sounds weird, but it's not bad) while Miriam whipped up some lemonade—and of course we added some purple cabbage juice...which reacted with the acidity of the lemons to turn the pitcher bright pink!