Experiment 1

Objective:  Determine Which Chemicals Are Acids and Which Are Bases

Introduction:

This experiment aims to distinguish between acids and bases using a natural pH indicator. Acids, such as those represented by the formula HA, have a pH lower than 7.0 and increase hydrogen ion activity in water. Robert Boyle defined acids as substances with a sour taste, corrosive properties, and a neutralizing reaction with bases. Bases, on the other hand, have the opposite effect of acids, decreasing the hydronium ion concentration and feeling slippery to the touch. Neutralization occurs when acids and bases are mixed.

Required Materials:

Red cabbage leavesWaterBowlColander (food strainer)VinegarLemon juice (fresh squeezed or lemonade)Bicarbonate of soda (baking soda)Laundry detergentSeveral glass jars (vials preferred)Eye-dropper (optional)

Procedure:

1.    Cut the cabbage leaves into small pieces.

2.    Boil several cups of water, enough to submerge the cut cabbage pieces.

3.    Soak the cabbage in a bowl by pouring the boiling water over the pieces. Let it sit for at least 30 minutes until the water turns dark purple.

4.    Strain the cabbage pieces using a colander or spoon, separating the purple cabbage juice.

5.    Set up the glass jars in a row, 1-2 inches apart. Pour a small amount of each chemical (vinegar, lemon juice, bicarbonate of soda, and laundry detergent) into separate jars.

6.    Test the chemicals by adding a dash of cabbage juice into each jar. Use an eye-dropper for precise measurement, and swirl the mixtures.

·       If the mixture turns pink, the chemical is an acid.

·       If the mixture turns blue or green, the chemical is a base.

Observation:

The cabbage juice acts as a natural pH indicator, changing color when mixed with acids and bases. The cabbage juice itself can be preserved for future experiments as a cost-effective indicator.

Questions:

1.    What other chemicals can you find around your house that could be good candidates for testing as acids or bases?

2.    Try using toothpaste, fruits, vegetables, and other common household items. How do they react with the cabbage juice?

3.    Is Gatorade a base or an acid? What about Dr. Pepper?

4.    Can you guess which are acids and which are bases before mixing them with cabbage juice?