Page 17 - Ranger PT3 2022 science

Science PT3 Chapter 2 Cell as the Basic Unit of Life
5. The following are the steps to test for the presence of starch in a green leaf:

Starch test
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1. Immerse the leaf in boiling water for one minute to Leaf Boiling
water
break down the leaf cells.

2. Immerse the leaf in a boiling tube that contains
alcohol and place it into hot water for a few minutes Alcohol
to remove the chlorophyll from the leaf. Hot water
Bunsen Form 1
burner off
3. After the leaf loses its colour, place it into the hot
Form 1
water to soften it and remove the alcohol.
Hot water

4. Add a few drops of iodine solution onto the leaf. If Iodine
the iodine solution turns dark blue, starch is present solution
in the leaf.
White tile

6. The following experiment shows factors that are required for photosynthesis:

(a) Presence of carbon dioxide
Variables:
Manipulated: Presence of carbon dioxide
Responding: Presence of starch
Constant: Presence of sunlight, water, and chlorophyll

Bell jar
Green plant Potassium
hydroxide
crystal
Glass plate
Vase A Vase B
Results:
Leaf Starch test Inference
A Dark blue Photosynthesis occurred
B Brown (No change) Photosynthesis did not occur
Sunlight
(b) Presence of sunlight
Variables:
Manipulated: Presence of sunlight
Responding: Presence of starch Black
Constant: Presence of carbon dioxide, water, and paper
chlorophyll

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