(b) Leaves can be tested for starch to show that photosynthesis has taken place.
This is the method given in a biology textbook.
1. Remove the leaf you want to test from the plant.
2. Half fill a 250 cm³ beaker with water and boil the water using a Bunsen burner.
3. Using a pair of forceps, hold the leaf in the boiling water for 20 seconds.
4. Turn the Bunsen burner off.
5. Using the forceps, push the leaf to the bottom of a boiling tube and cover it with ethanol.
6. Place the boiling tube in the beaker of very hot water. The ethanol will boil.
7. When the leaf is colourless, remove it from the boiling tube and wash it in cold water for
a few seconds.
8. Place the leaf flat on a white tile.
9. Add dilute iodine solution with a pipette, making sure the whole leaf is covered.
10. Any starch present will react with the iodine solution.
(1) Explain a safety precaution that should be taken when carrying out this test.



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