Biology Photosynthesis Lab
Biology lab
AIM: To test a leaf for starch
APPARATUS/MATERIALS : * bunsen burner, tripod stand, wire gauze(OR 90oC electric water bath OR hot plate) * 250 cm3 beaker * boiling tube * anti- bumping granules * forceps * test tube holder * white tile * leaf to be tested (hibiscus leaves are excellent) * 90% ethanol * iodine/potassium iodide solution
PROCEDURE:
The video above shows the steps in Testing a Leaf for the Presence of Starch. The Procedure outlined below is slightly different. 1. Remove a green leaf fom a plant that has been exposed to sunlight for a few hours 2. Half-fill a 250cm3 beaker with water. Heat the water until it boils. Keep the water at boiling point. 3. Use the forceps to place the leaf in the boiling water. Boil for 2 minutes. 4. Turn off the Bunsen Burner. (If you are using a heat source without a naked flame - electric water bath or hot plate - this step is uneccesary.) 5. Place the boiled leaf in a boiling tube containing 90% ethanol. 6. Place the boiling tube in hot water and boil for 10 minutes or until the leaf decolourizes. ( It may be necessary to replace the ethanol) 7. Gently remove the leaf and wash with a fine trickle of cold tap water. 8. Spead the leaf evenly on a white tile. 9. Add a few frops of iodne/potassium iodide solution to the leaf and note any observations.
OBSERVATIONS/RESULTS: * The leaf was flaccid (soft) after being boiled in water * The ethanol changed from colourless to green * The leaf was brittle after being boiled in ethanol * The leaf become flaccid once more after being rinsed in cold water | OBSERVATION | INTERPRETATION | POSITIVE TEST | Iodine/Potassium Iodide solution changed from brown to blue- black | Starch is present | NEGATIVE TEST | No colour change | Starch is not present |
DISCUSSION QUESTIONS AND ANSWERS 1. Describe Photosynthesis. Use a symbol equation.
Photosynthesis is the process
AIM: To test a leaf for starch
APPARATUS/MATERIALS : * bunsen burner, tripod stand, wire gauze(OR 90oC electric water bath OR hot plate) * 250 cm3 beaker * boiling tube * anti- bumping granules * forceps * test tube holder * white tile * leaf to be tested (hibiscus leaves are excellent) * 90% ethanol * iodine/potassium iodide solution
PROCEDURE:
The video above shows the steps in Testing a Leaf for the Presence of Starch. The Procedure outlined below is slightly different. 1. Remove a green leaf fom a plant that has been exposed to sunlight for a few hours 2. Half-fill a 250cm3 beaker with water. Heat the water until it boils. Keep the water at boiling point. 3. Use the forceps to place the leaf in the boiling water. Boil for 2 minutes. 4. Turn off the Bunsen Burner. (If you are using a heat source without a naked flame - electric water bath or hot plate - this step is uneccesary.) 5. Place the boiled leaf in a boiling tube containing 90% ethanol. 6. Place the boiling tube in hot water and boil for 10 minutes or until the leaf decolourizes. ( It may be necessary to replace the ethanol) 7. Gently remove the leaf and wash with a fine trickle of cold tap water. 8. Spead the leaf evenly on a white tile. 9. Add a few frops of iodne/potassium iodide solution to the leaf and note any observations.
OBSERVATIONS/RESULTS: * The leaf was flaccid (soft) after being boiled in water * The ethanol changed from colourless to green * The leaf was brittle after being boiled in ethanol * The leaf become flaccid once more after being rinsed in cold water | OBSERVATION | INTERPRETATION | POSITIVE TEST | Iodine/Potassium Iodide solution changed from brown to blue- black | Starch is present | NEGATIVE TEST | No colour change | Starch is not present |
DISCUSSION QUESTIONS AND ANSWERS 1. Describe Photosynthesis. Use a symbol equation.
Photosynthesis is the process