Magic Painting with Acids and Bases

I've been "on the road" training a bit again this week.  On Monday night I presented on Life Science and Life Cycles here in Marquettte. Wednesday, I presented a variety of simple science experiences in Menominee. One of the many things we ran out of time before we were able to finish was testing for acids and bases with a red cabbage indicator.  So, yesterday, I whipped up a batch of indicator paper with some of the cabbage.
You will need to cut up some red cabbage (purple in color), and place it in some hot water. I prefer to boil the cabbage for a few minutes as this expedites the process. I know that you can allow the cabbage to sit in water, to get the same result; but that takes longer!
Then, strain your cabbage so that you are only left with the colored water. It will be a deep blue/purple color. This cabbage water serves as an indicator for investigating acids and bases. You can just use the liquid, but I wanted to create some indicator strips for dipping into liquids/solutions.  So, I took regular paper and I dipped it in the "purpley" water.

You want to watch the paper to make sure that it gets fully saturated, but at the same time, you don't want to over do it so that the paper rips when you remove it. This is a process that you could easily involve the children in. However, I wanted to make this paper a surprise for my little ones, so I did this while they were napping ;).
 The paper will be very wet. I gently placed it on a towel before setting it on our table outside to dry.  While the paper was drying in the sun..... I had a brilliant idea! (I do come up with my own ideas from time to time). What if instead of cutting the paper into strips, we paint on it with various liquids and solutions to "see what happens?"  So.... We did some magic painting!
I looked to see what I had around that house that I knew would work well. I made up 3 small jars of "paint" One is a solution of baking soda and water (a base), another was lemon juice (citric acid), and the last one is vinegar (acid).

After trying the paper out myself, I decided that it made great testing strips, but the colors for painting on regular paper weren't very vibrant. So...... I grabbed a stack of coffee filters and saturated those with the cabbage juice instead! The filter paper is much more absorbent, and the magic color changes work so much better!

To see the "magic" work, I gave each child a piece of white card stock for under their filters. (On our wooden table, it is hard to see the colors!). They were pleasantly surprised to see that the lemon juice did not produce a yellow paint, but a bright pink one, and the cloudy water turned green on the paper!!! How did that happen? It had to be magic!  The vinegar also turned pink, but was slightly lighter than the lemon juice.

As we painted and painted, I did my best to answer all of the children's questions. Then, I told them how I made the paper and we talked a little bit about acids and bases. (They all remember doing the penny experiment, and they all remember what happens when you mix vinegar and baking soda!) Maybe when they grow up and start learning more about chemistry, they will remember how a "magic" indicator changes acids pink and bases green, and if they don't remember, that's okay too! They sure had fun with their "magic" paper, and I'm sure this will not be the only time we paint with it!

This post was linked up over at:

PreK + K Sharing


Wow! This would definitely make science fun! :) You're awesome. Just thought you should know.
Ticia said…
I've had this sitting in my google reader for a couple of days so I can remember to put cabbage on my grocery list.
Meg said…
This is fantastic! What a great way to integrate science and art, Thanks for the idea!
The Adventurer said…
Great idea we are studying acids and bases right now:)
Annette said…
this just looks fun to do. linked it on my blog. (anetintime)

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