Testing pH (using household items)

I was FLOORED to discover how easy it is to make your own "safe" pH indicator.

Red cabbage juice has a pH of 7, changes to shades of reds with the addition of an acid and shades of green and yellow when adding a base. It remains blue and purplish closer to neutral (7).

Shred or even pick out from a salad mix bag shredded red cabbage. I used only one cup of red cabbage to get nearly a jar full of juice. I've read different variations for the water to cabbage ratio, but I did 1:1 and that worked very well.

The steps are simple:

1. Pour one cup boiling hot water over 1 cup red cabbage.
2. Let sit for at least 15 minutes or until it doesn't look like the juice is getting darker.
3. Strain the cabbage out using a pasta strainer.
4. Repeat if it looks like your cabbage still has a lot of purple pigments or you want additional juice. I poured a second cup of water over my cabbage & drained. I think I may have been able to do a third round as well, but I really didn't need any more juice.

I tested the whole experiment at home to make sure the color changes actually worked and to just experiment with the results of different products in the home. I ended up going with the following acids and bases which produce these colors pictured below. In order from left to right:

• Hot sauce
• Vinegar
• Milk
• None/Control/Red Cabbage Juice
• Baking Soda
• Detergent
• Bleach

I created a worksheet for kids to record their experiment results. We started by coloring the key at the bottom and discussing what is the pH scale, acids, and bases. I had kids try to predict whether they thought certain things were acids or bases or what color they might change. I explained that the cabbage juice alone has a neutral pH, which is why we can use it as an indicator.

Cool trick for older kids- after you do all your tests, experiment mixing two solutions. If you are to mix a strong base and a strong acid, the two should cancel each other out and return to neutral (purple)! Math can easily be incorporated into this.

When we began, everyone had their own beaker cup and chance to do each test.... towards the end we ran out of time, so we did the last two as a group.. Having multiple jars of the indicator and acid/bases would have helped as I had to walk around with the jar to all the tables.