What it shows
Guava contains oxalate ions. Titrating extracts of raw, half-ripe and ripe guava with potassium permanganate shows how the amount of oxalate changes as the fruit ripens.
This idea has a short entry only. For the science behind it, read the sentence above with your textbook and ask your teacher to explain the law or idea it shows, so you can describe it in your own words.
Materials
- Guavas at three stages of ripeness
- Potassium permanganate solution and dilute sulphuric acid
- A burette, a pipette and conical flasks
- Filter paper and a mortar and pestle
Safety
For this project: This uses an acid and an oxidiser: do it only in the school lab with your teacher, wearing goggles and gloves.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
How to go about it
Numbered steps have not been written for this idea yet. Plan it with your teacher: sketch the design with measurements, build one part at a time, test each part, and write every observation with the date. The free ebooks below have step-by-step projects of the same kind.
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