This document describes an experiment using red cabbage juice as a pH indicator. Red cabbage juice contains the pigment anthocyanin, which changes color based on whether the solution is acidic or basic. In the experiment, red cabbage juice is tested against various household substances to determine if they are acidic, basic, or neutral by observing the color change in the cabbage juice. Water does not cause a color change in cabbage juice because it is neutral, with a pH of 7, while acids cause the juice to turn red and bases cause it to turn greenish-blue.

1. Red Cabbage Chemistry
Andrea Leigh Fontanilla 9 - Newton

2. In this experiment we will test and try to
know the pH levels of these substances, whether
it is basic, neutral or acidic. Let us try to see
what will happen if we add the test chemicals to
the red cabbage juice.

3. Materials:
 red cabbage
 blender or knife
 boiling water
 filter paper (coffee filters work well)
 One large glass beaker or other glass container
 Six 250 mL beakers or other small glass containers
 household ammonia (NH3)
 baking soda (sodium bicarbonate, NaHCO3)
 apple cider
 lemon juice (citric acid, C6H8O7)
 vinegar (acetic acid, CH3COOH)
 orange pop
 Laundry Detergent or Bleach
 muriatic acid or masonry's cleaner (hydrochloric acid, HCl)
 lye (potassium hydroxide, KOH or sodium hydroxide, NaOH)

4. Procedure:
 Chop the cabbage into small pieces until you have about 2 cups of
chopped cabbage. Place the cabbage in a large beaker or other glass
container and add boiling water to cover the cabbage. Allow at least ten
minutes for the color to leach out of the cabbage. (Alternatively, you can
place about 2 cups of cabbage in a blender, cover it with boiling water,
and blend it.)
 Filter out the plant material to obtain a red-purple-bluish colored liquid.
This liquid is at about pH 7. (The exact color you get depends on the pH
of the water.)
 Pour about 50 - 100 mL of your red cabbage indicator into each 250 mL
beaker.
 Add various household solutions to your indicator until a color change is
obtained. Use separate containers for each household solution - you don't
want to mix chemicals that don't go well together!

5. Conclusion
Some substances are classified as either an acid or a
base. Think of acids and bases as opposites - acids have a
low pH and bases have a high pH. For reference, water (a
neutral) has a pH of 7 on a scale of 0-14. Scientists can tell
if a substance is an acid or a base by means of
an indicator. An indicator is typically a chemical that
changes color if it comes in contact with an acid or a base.
As you can see, the purple cabbage juice turns red
when it is mixed with something acidic and turns green
when it mixes with something basic. Red cabbage juice is
considered to be an indicator because it shows us
something about the chemical composition of other
substances.

6. What is it about cabbage that causes this to happen?
Red cabbage contains a water-soluble pigment
called anthocyanin that changes color when it is mixed
with an acid or a base. The pigment turns red in acidic
environments with a pH less than 7 and the pigment turns
bluish-green in alkaline (basic) environments with a pH
greater than 7. Red cabbage is just one of many indicators
that are available to scientists. Some indicators start out
colorless and turn blue or pink, for example, when they
mix with a base. If there is no color change at all, the
substance that you are testing is probably neutral, just like
water.

8. 1. It is a chemical that changes its color if it
comes in contact with an acid or base.
2. What causes the Red Cabbage juice to change
its color?
3. Why is that there are no color changes that
happened when water was mixed with the Red
Cabbage juice?