Question

During the lab, you will have access to a range of acids and bases as well as universal pH indicator paper. Think about how you can use these tools to develop a color chart for the red cabbage indicator. Then, write a hypothesis using the “if/then” format.

Answer 1

Plan to develop a red cabbage indicator color chart
- Prepare a concentrated red cabbage extract (boil chopped cabbage in water, filter). Use the same extract batch for all tests.
- Label a series of clear test tubes or cups for a range of target pH values (for example: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14).
- Using the available acids and bases, make solutions that span the pH scale. For each solution, confirm its pH with the universal pH indicator paper and record the measured pH.
- Add the same small volume of red cabbage extract to each labeled solution (keep volumes constant). Allow colors to develop and mix thoroughly.
- Record the resulting color for each measured pH (take photos and/or make colored swatches under the same lighting). Repeat each test at least once for reliability.
- Compile the colors matched to the measured pH values into a chart. Note any gradual shifts or unusual transitions (e.g., purple near neutral, red in strong acids, blue/green in bases).

Control and consistency tips
- Use identical volumes, same extract concentration, same container type and lighting.
- Rinse instruments between solutions to avoid contamination.
- Record temperature if it varies (color can be slightly temperature-sensitive).

Hypothesis (if/then format)
If red cabbage indicator is added to solutions across the pH scale, then the indicator’s color will change systematically with pH: it will be red/pink in acidic solutions (low pH), purple around neutral (pH ≈ 7), and blue/green in basic solutions (high pH), allowing a color chart to be made that correlates specific colors with measured pH values.