Saturday, April 4, 2009

Acid or a Base? Indicator strips

You can make your own PH indicator strips. Test all kinds of liquids with them to see if they are an acid, a base or neutral.

Did you know that red cabbage juice changes color when a base or acid is added? Oh the fun you can have with red cabbage juice!!

What you will need:
small red cabbage
paper towels or coffee filters
sheet of white paper
colored pencils
solution liquids to test- Lemon and orange juice, vinegar, milk, tap water,soapy water,yogurt and, baking soda in water, salt in water, just to name a few.
glasses or paper cups

Step 1: Chop into small pieces 1/2 a small red cabbage. Put the chopped cabbage into a saucepan with just enough water to cover it. A parent should boil it for 20 to 30 minutes. Until the liquid turns a dark purple color. To make it stronger simmer uncovered to reduce the water content a bit.

Step 2: Let the cabbage juice cool and then strain into a jug or container.

Step 3: Cut 2 inch strips of paper towels or coffee filters.

Step 4: soak the strips of paper in the red cabbage juice until they turn bluish purple.

Step 5: Lay the wet strips flat to dry. These are you indicator strips.

Step 6: Label the cups and fill each with a different liquid to test.

Step 7: Use the indicator strips to test the liquids. Dip your strips in the liquids. Start with something like vinegar and explain that it is an acid. Then test baking soda in water and explain that it is a base (alkali for older kids). Wait a few minutes for the color to fully develop.

Step 8: Make a chart and label by dividing a piece of white paper into 3 sections. Label the first section "Acid". The middle section "Neutral" and the last section "Base". Then have your child make squares for the vinegar (in the acid column) and the baking soda (in the base column). Now let your child test other liquids around the house. Then have them tell you if they are an acid, neutral or a base. Label them on your chart. You can print out mine if you like.

Why this works:

Your cabbage juice is a simple pH tester. The pigments in the red cabbage react differently to different substances, acids and bases.

When you dip your strips into your substance and wait a few minutes the color will fully develop.

The strips will turn red-yellow in acid. Green in neutral and purple blue in bases (alkali).

Don't throw away your un-used red cabbage juice!!! Save it and put it in the fridge.
I will show you how to make a color change volcano! I will be posting the instructions for it Soon!!


the monkeys' mama said...

wow! i never knew this and I was a biology nerd forced to take chemistry. This would have made pH tests much more interesting :)

erika said...

very cool!

Lucky Mom said...

Super neat. Can you remind me of these topics in December/January - right before Science Fair project pickin' time?? They are great.

Ferrers Locke said...

Finally, I'm catching up with the blogosphere! Thank you for this. The girls will have fun with it, and with the colour changing volcano. So will I.