B1.4.2 Photosynthesis Experiments Flashcards
How do you test for starch to prove that photosynthesis has taken place? (6)
Place leaf in boiling water for 1 minute to kill it
Place in boiling tube with ethanol
Place boiling tube in a water bath an boil until white (chlorophyll removed)
Wash leaf with water to remove ethanol and soften
Place on white tile and add 1-2 iodine drops
Watch for colour change in iodine (blue/black)
Why does chlorophyll have to be removed to test for starch? (2)
Chlorophyll is where glucose is made, which is later converted in starch.
Leaving it would mean the plant cause inaccuracy
How do you prove that chlorophyll is needed for photosynthesis? (4)
Variegated leaves only have chlorophyll in some areas of the leaf.
This means some areas of the leaf appear green, whereas others are white.
To prove chlorophyll is needed you should place a destarched variegated plant in sunlight for several hours.
You then test one of its leaves for the presence of starch
How can you prove light is needed for photosynthesis? (4)
To prove light is needed for photosynthesis take a destarched plant and cover part of one of its leaves with black card or tin foil.
Light cannot reach the covered area of the leaf.
Place the plant in sunlight for several hours.
Finally, remove the card from the leaf and test the leaf for the presence of starch
Why would iodine added to variegated leaves only turn blue-black on green areas? (2)
Because the white areas have no chlorophyll, so they won’t have chloroplasts, and can’t produce glucose to make starch.
The green areas can, so the starch turns the iodine blue-black.
How can you prove that carbon dioxide is needed for photosynthesis? (4)
Take a destarched plant and place it inside a polythene bag
Before you seal the bag, add a pot of soda lime
Place the plant in sunlight for several hours
Test one of the leaves for the presence of starch
How can you prove oxygen is given off (4)
Place an upturned test type over pondweed
Put the apparatus in light for maximum photosynthesis
When you’ve collected a tube full of gas, place a glowing splint inside the tube
It’ll relight if oxygen is present
What is soda lime
A chemical that absorbs carbon dioxide and water vapour
How to prove glucose is produced
Take a leaf to sample, submerge it in boiling water to kill it.
Then submerge it in boiling ethanol to remove chloroplasts before washing and placing on a white tile.
Add a few drops of iodine solution to see if the colour changes from yellow-brown to blue-black
