Chemistry in the Kitchen...Acids and Bases

Next time you go to the grocery store, pick up a red cabbage for a little science fun with acids and bases.  Red cabbage (which actually is purple) makes an excellent indicator.  That means it reacts to acids and bases in a way that is easy to measure.
Step 1  Prepare your indicator
There are several ways you can prepare your indicator.
Method 1:  Chop one-fourth of a head of cabbage into a few big pieces. (I use the bottom part and any parts that might be thrown away.)  Put the cabbage in a pan with 3 to 4 cups of water.  Boil until the cabbage is pale and without color.  Water should be purple. Strain out cabbage. Let the liquid cool.
***You can use the indicator as a liquid or use it as a dye for coffee filters or card stock to make indicator paper.  The down side is you have to let it dry before using.
Method 2:  This makes quick liquid indicator.  The results will be blue not purple.  It will work but not as well.  To make, coarsely chop one third to one fourth of a head of cabbage.  Fill a blender one half full of cabbage.  Add enough water to just cover the cabbage.  Coarse blend for 1 minute until water becomes dark blue.  Strain out cabbage.  Repeat process for more liquid indicator.
Note: This method will not work as well as the first method but will still get results.
Method 3:  (this is my preferred method...it is less work to prepare and clean.  Also, I like that kids are involved in creating the indicator). You will need (1)  a piece of cabbage (about 1/3  to 1/4 of a leaf, also the thicker the easier to handle) (2) a piece of  card stock or an index card (you can use regular paper but it may tear. (3) some q-tips
Rub the cabbage on the card until you have most of the card purple.  You will need to rub very hard.
Step 2  Collect your substances to test
Suggested substances are: bar soap, liquid soap or shampoo, vinegar, window cleaner, lemon juice or other citrus
Step 3 Test your substances