Can red cabbage be used to make an effective indicator?
We used methylated spirits (ethanol with 10% methanol added) to extract the colouring from some red cabbage. This was then added to a range of different pH values to see if it changed colour. A reliable and obvious colour change, at a given pH, would qualify the home-made indicator as effective – the word used as a qualifier in the investigation title.
The boys used iPads to photograph their results.
Each solution was tested twice so that we could avoid anomalous results. Any non-identical pairs could be tested again to ensure that no errors were made.
The solutions ranged in pH from 14 to 1, with distilled water being used to provide a pH of 7.
Questions…
- Why do you think methylated spirits has poisonous compounds like methanol added to it?
- Ethanol is a compound of carbon, hydrogen and oxygen. What two products would be produced if it burned completely in air?
- What process in yeast produces ethanol (alcohol) as a by-product?
- What solutions might have been used to provide a range of pH values? Suggest some solutions and their approximate pH.
- Which major food group does cabbage contribute to your diet?
- Suggest three ways in which a cabbage cell might differ from a human cheek cell.
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