Kitchen Chemistry

ph-test.jpg

You’ve heard of the litmus test, but have you tried the cabbage juice test? I’m home schooling the kids, as the greeting says, and Thing 1 is working on a chemistry science unit at present. After she did her work with litmus paper, I made her some cabbage juice indicator. We didn’t try all the liquids she tested with litmus paper, but this pretty clearly shows the pH range (the milk of magnesia is basic and turns green, water is neutral and is bluish-purple, and vinegar is acidic and turns bright pink). I also showed her how you can tell when you have neutralized an acid or base. If you would like to play with this in your kitchen, all you need is a head of red cabbage and water . . . and whatever you what to test.

Boil 2 cups of water.

Add chopped red cabbage and let soak for 30 minutes. Strain out the cabbage and collect the liquid.

Add a few tablespoons of rubbing alcohol (isopropanol) if you want to keep your indicator around for a few weeks.

Have fun testing the pH of things in your home. The kids have a blast with this! πŸ˜€

** Safety caution — don’t taste this stuff! πŸ˜‰

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6 Responses

  1. When you are really careful about the pH of the liquid used to make the indicator you can make a beautiful rainbow of colors. It is definitely a fun experiment! We did this once for junior high students but they decided to mix the bleach with drain cleaner. Yeah, that was a pleasant smell. What color was your indicator solution initially, purple or blueish?

  2. It’s definitely purple.

    The hard part of this was the two littlest things wanted to drink the ‘pretty juices’ we made and I kept having to tell them NO!

    Even Thing 1 got her nose a little too far into the ammonia bottle and I told her that just b/c we could buy this stuff at the Grocery Store and just b/c we were doing it in the kitchen, did NOT mean that she could just mix any old thing together, sniff any old thing, or taste any old thing. We don’t need to be in the chemical weapons business! πŸ˜‰

  3. I have found that purple works better. You must have really good water.

  4. I graduated with a chemistry degree, so you can figure that I LOVE this!!! I’ve never heard of the cabbage litmus test. How much fun! This is something they should be doing in public/private schools as well.

  5. Claire — I don’t often mention it these days, but as an undergrad I double majored in chemistry and history and then went to grad school and got my master’s in chem (and my MRS!) πŸ˜‰

    After that, while the Husband was getting his Ph.D. at a different university than the one at which we met, I spent 18 mos working at the state headquarters for an insurance company before finding a job that fit my educational background. I then worked for 3.5 yrs doing EPA drinking water analysis for the state of New Mexico. By then, Thing 1 had come along so I ‘retired’ and started my next career path — SAHM and home school teacher.

    It’s a lot of fun to be able to do this kind of stuff with my girl and she’s very excited that it’s the stuff that both Mom and Dad ‘went to school to learn’. I’ve seen this cabbage pH indicator in almost every ‘kitchen science for kids’ book I’ve looked at, but this was the first time I’ve tried it out. It works wonderfully! We did a little ‘titration’ with milk of magnesia and vinegar and it was nice to be able to see the transition from basic to neutral and then we pushed it on to acidic and she could tell me what was going on. You’ll have to try it out! πŸ˜‰

  6. This is very cool! Like a micro experiment…

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