science for tinies: color-changing cabbage chemistry

[psocoptera]

Project: What Will The Color Be?
Materials: Color-changing cabbage liquid (boil red cabbage in water for about ten minutes, let cool, strain, keeping liquid and discarding leaves; I used about a quarter of a cabbage and 2-3 cups of water), white vinegar, lemon juice, baking soda solution (put a few spoonfuls of baking soda into half a glass of water, microwave briefly to warm, stir), experiment vessels (a white or clear molded plastic tray from a box of candy makes a terrific well plate, with lots of small compartments for repeating your experiment - keep your eyes open during the holiday season when there's lots of candy going around. you can also use a muffin tin, an ice cube tray, or just lots of little bowls)
Explanatory details: Junie spooned out purple cabbage liquid into the 12 wells of the tray. I helped her add water to one (no color change), lemon juice to one (turns bright pink), vinegar to one (bright pink), and baking soda solution to one (turns blue-green). Then I let her try a bunch of repeats on her own. Once every well on the tray had been used, we tried adding vinegar to a green well and baking soda to a pink well to see if we could turn them back to purple, and she messed around with that some more.
How did it go: This was *great*. We had just done some fizzy science recently, testing water, vinegar, lemon juice, and milk with baking soda, so we were primed for looking for same and different reactions, and we (sort of) knew what was going on when we added vinegar to a green (baking soda) well and it started fizzing! (Fizzy science is our third-most requested science activity, after duck science/icecube science (chucking things into a tub of water) and flashlight colors.) The cabbage liquid was super-easy to make and the colors were nice and bright and obvious on our white tray. I had put small amounts of vinegar, water, etc into little dishes and felt comfortable letting Junie spoon it out herself, which she did quite carefully with a minimum of countertop mess; I did remind her a couple of times to keep her fingers out of her science. We have tons of cabbage liquid left and will definitely do this again - I'm going to see how well it freezes for future use (and will report back on that).
Things we talked about: The cabbage liquid is a pH indicator - I briefly caught myself starting to use the words "acid" and "base" and had to back up and rethink my approach. Junie only listens to about one sentence of explanation at a time, so I think at this age "acid" or "pH" would just be nonsense words, what I wanted to emphasize was:
- a given thing (vinegar, baking soda, water) gives the same color every time you add it to a fresh well.
- vinegar and lemon juice are the same, they both turn it pink.
- baking soda is different, it turns it green.
- baking soda can turn a vinegar well back to purple. vinegar can turn a baking soda well back to purple. vinegar and baking soda are opposites.
- adding water doesn't change the color, whether it's purple, pink, or green.
What Junie got out of it: She loved it. She enjoyed helping me rip up cabbage to put in the pot and was very pleased to get to spoon out purple liquid into the wells. She was fascinated by the changing colors and got particularly interested in adding more things to the same well to try to change the color back and forth or back to purple. One thing that was interesting was that I hadn't labeled the dishes with the vinegar, baking soda solution, etc, but had put them in different kinds of bowls so that I could keep track of which - Junie definitely wanted specific ones to try next and would check "is this the vinegar" etc. I think next time I do it I'll try putting masking-tape labels on with a letter V for vinegar, BS for baking soda, etc, so that she can more confidently know which is which (and because it's a good idea to start teaching her to always label!).

Comments

[mst3kforall.livejournal.com]

Once again, wonderful experiment well adapted to tinies. If you wanted to, I believe that you could collect these into a book (perhaps when Junie is older?) and possibly even sell them to a publisher. I think it is an open market, that there is a boom of parents with young children, and that there are a lot of parents who would like to teach their children but may not have the creativity and cleverness and wherewithall to design them, and that the experiments/demonstrations are great. Even telling how Junie responded would be very appealing in a book, although I don't know whether you are comfortable sharing that much. And this may not be an idea you wish to pursue, but I wanted to tell you about it because they are so cool!

[prof-fran.livejournal.com]

I love reading them. I agree completely. It may not be something you're interested in but I think it would be really well received. One of the things I like best is that you have such a personal voice and style that is really approachable. And you've thought these out carefully and tried them out (and isn't that why you're having the next one, to widen the sample size? :)

[gannet.livejournal.com]

T has always loved pH things.

Something fun for later - you can dye wool yarn with black bean juice and then change its color with acids and bases, because black bean juice has the same or a similar pH indicator in it.

[rahirah]

That's really nifty!