From making fertilizer and plastic to keeping your body healthy, acids and bases are
important to a variety of areas of your life. If you are curious about what substances
around your house are acids and bases, you can make an indicator from a red cabbage.

An indicator changes color depending on whether it comes in contact with an acid or
base. The juice from a red cabbage can indicate the following:

Color Change	What It Means
Red/Pink	Really acidic
Pinkish Purple	Slightly acidic
Dark Purple	Neutral (neither acidic or basic, like water)
Blue	Slightly basic
Green/Yellow	Really basic

Procedure

Here is the procedure for making red cabbage juice. Please have an adult help you with
EVERY step.

1. Chop up a head of red cabbage and put it in a bowl that can withstand heat (if you
   have too much cabbage to fit in one bowl, you can just repeat the following steps
   several times or not use the entire head).
2. Pour boiling water over the cabbage.
3. After 10 minutes, pour the mixture through a strainer into another container. I
   usually pour it into a large, glass measuring cup in the sink. The spout of the
   measuring cup then allows me to pour it into an empty 1 gallon milk jug to use for
   storage.
4. Throw away the used cabbage.
5. If you do not use the entire amount of cabbage juice and you would like to save it
   for later, put it in a sealed container in the refrigerator. If you would like to keep it
   for even longer, you can pour the liquid into ice cube trays and freeze it.

Once you make your cabbage juice, you are ready to test the pH of different substances.
Here are some suggestions:

colorless soda (like Sprite) washing detergent dissolved in water drain cleaner carbonated water tap water antacids dissolved in water vinegar

washing soda dissolved in water lemon juice baking soda dissolved in water ammonia milk sugar dissolved in water rubbing alcohol

Pour a small amount (less than half-way up the container) of your collected substances each in their own small, colorless cup (medicine cups work well or see-through bathroom cups). Add about an equal amount of red cabbage juice to each substance. Observe what color it becomes and determine whether it is acidic, basic, or neutral using the chart above.

The Science Behind the Effect

An acid is a chemical that produces H+ (hydrogen ions) in water. A base is a chemical
that produces OH- (hydroxide ions) in water. Acids and bases are commonly found in everyday life.

The pH of a solution tells us whether it is an acid or a base. If the pH of a liquid is less than seven, then it is an acid. If the pH of a liquid is greater than seven, then it is a base. If the pH equals seven, the liquid is neutral.

Indicators are another way of determining whether a substance is an acid or base by looking at color changes. Red cabbage juice contains pigments (something that causes color) called anthocyanins that make it purple. Anthocyanins can be found in the petals of flowers and even the leaves of trees (that is why some tree leaves become red in the fall). Anthocyanins change color depending on the amount of H+ and OH- present, therefore telling us whether the substance is an acid or base.