Red Cabbage Does Stuff
What you will need for this experiment:
What To
Do:
- Grate 1/2 the cabbage into a bowl. Fill the bowl with water
and let it sit for a couple of hours. Drain the cabbage water into the other
bowl. OR. Put the grated cabbage into the saucepan with enough water to just
cover it. Boil for 20-30 minutes until the liquid turns a dark purple
colour.
- Let the cabbage juice cool and then strain into the
jug.
- Cut 2 inch (5 cm) strips out of the paper towels/coffee
filters.
- Soak the strips of paper in the cabbage juice until they
turn bluish-purple.
- Lay the strips flat on the bench/table and leave
them to dry. These are your indicator strips.
- Put the other
liquids (lemon juice etc.) into separate cups.
- Dip the indicator
strips into one liquid each.
- Using pencils and your plain paper,
copy the colour that each strip turns.
- Draw a picture, or write the
name of the liquid that made the paper turn that colour.
- Use your
notes to make a chart showing the different colours that the liquids
produced.
What Happens:
Your red cabbage juice is a simple
pH tester. It reacts differently to different substances. Once you know
what colour the juice turns in acids and alkalis, you can use it to test
other liquids.
Why It Happens:
Red cabbage has pigments which
react differently to acids and alkalis. When you dip the strips into a
substance and wait for a few minutes, the colour will fully develop. The
indicator strips turn red-yellow in acid, green in neutral and purple-blue
in alkali.