Color Change Chemistry 3
On the second and first experiments, I used chemicals. But this time, I’m going to use grapes. Grapes contain a pigment molecule called flavin (an anthocyanin). This water-soluble pigment is also found in apple skin, plums, poppies, cornflowers, and red cabbage.
Things you’ll need: Black grapes, alcohol lamp, beaker, water, test tubes, test tube holder, vinegar, borax, a funnel, and a pipet.
- Put grapes into the beaker and fill it with water until it’s above the grapes.
- Set the alcohol lamp (you can use a stove instead of the lamp and a pot instead of a beaker).
- Wait until the water boils, then turn off the heat and let it cool.
- Use the funnel to take the grapes out.
- Pour vinegar into the first test tube. Pour water in the second. And pour water + borax into the third. Now we have acid to base.
- Drop 2-3 drops of the grape juice into the test tubes (if nothing happens keep adding the grape juice).
Very acidic solutions will turn anthocyanin a red color. Neutral solutions result in a clear color. Basic solutions appear in greenish-yellow. Therefore, it is possible to determine the pH of a solution based on the color it turns the anthocyanin pigments in grape juice.
Extra steps:
7. Pour the first and the third test tube together.
8. You will have the same colors.
Danupon Drake 