The pH scale indicates the kind of ions a solution releases when it breaks down. Acidic solutions possess lots of hydrogen ions and basic solutions possess lots of hydroxide ions. Acidic substances have a pH below 7. Basic substances have a pH above 7. Neutral substances have a pH of 7. A pH indicator can be used to test the acidic or basic properties of other substances.
Read Aloud: Cool Chemistry Concoctions by Joe Rhatigan
Ingredients:
· Red Cabbage Juice
· Test Substances
· Eye Droppers
· Egg Cartons
Demonstration:
· Pour a tablespoon of each test substance into the individual compartments of an empty egg carton. Test substances can include: lemon juice, shampoo, vinegar, detergent, soda, milk of magnesia, orange juice, ammonia, coffee, hand soap, milk, and water.
· Add a few drops of the cabbage juice to the test substance in each compartment using an eye dropper.
· Note how each test substance changes color. Compare these colors to a pH scale to determine if each test substance is an acid or a base.
Experiment:
· What is the most acidic test substance?
· What is the most basic test substance?
Observations:
Most substances are classified as either an acid or a base.
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. The cabbage juice turns red when it is
mixed with something acidic (an acid) or green when it mixes with something
basic (a base). If there is no color change at all, the substance that you are
testing is probably neutral.
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