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Aim: To make acid-base indicators using everyday substances
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Equipment: Red cabbage, tea, beetroot, cranberry juice, a beaker, hot water, spotting tile, glass measuring cup, 1.0 mol L-1 HCI and 1.0 mol L-1 NaOH
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Method: For cabbage and beetroot
- Put 50ml of hot water into glass measuring cup
- Put small pieces of cabbage/beetroot into glass measuring cup with the hot water an stir
- Put a few drops of 1.0 mol L-1 HCI in the spotting tile
- Put a few drops of mol L-1 NaOH in the spotting tile
- Use a dropper to collect the water from inside the glass cup
- Add the water to each of the chemicals of the spotting tile and see what color they turn
- Once finished rinse measuring cup and dropper for next one
- For the tea
- Put 50ml of hot water into the glass measuring cup
- Put the tea flakes into the hot water and stir
- Put a few drops of 1.0 mol L-1 HCI in the spotting tile
- Put a few drops of mol L-1 NaOH in the spotting tile
- Use a dropper to collect the water from inside the glass cup
- Add the water to each of the chemicals of the spotting tile and see what color they turn
- Once finished rinse measuring cup and dropper for next one
- Put the cranberry juice into both of the chemicals in the spotting tile
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Discussion:
What colour did each indicator change in an acid vs. a base? Red cabbage – acid was pink – base was green. Beetroot – acid was light pink – base was light yellow. Tea – acid was yellow – base was brown. Cranberry juice – acid was light red – base was dark green.
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Why did indicators change colour? The indicators changed colours because they reacted with acids and bases
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Why did different household chemicals change different colours? Different household chemicals changed colours because cabbage, beetroot, tea, and cranberry juice contain natural dyes that act as pH indicators
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How did you know if these chemicals were acidic or basic? You knew if the chemicals were acidic or basic by looking at how they changed colours when mixed with the plant juices.
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Why might Universal indicator be more useful than Litmus paper? Universal indicator is more useful because it tells you exactly how strong an acid or base is
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Conclusion:
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did all your experiments work – if they didn’t, why? Yes all of my experiments worked
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What could you do to improve your science next time? Measure carefully: Use the exact same amount of water, plant pieces, and drops of chemical every time
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How could you make your results more reliable? (think about human error). Repeat the test: Do each juice test two or three times to see if you get the exact same color change every time. Avoid mix-ups: Use a different dropper for each chemical (one for HCl and one for NaOH) so you do not accidentally contaminate or mix them together by mistake
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