Page 18 - Focus PT3 2020 Science ( BI Version )

Science PT3 Chapter 2 Cell as the Basic Unit of Life

Sunlight
Sunlight

Air without Air Form Form
carbon dioxide Bell jar
1

Potassium hydroxide solution
Glass plates with vaseline
Green plant M Green plant N
Figure 2.19 The set-up of apparatus
3. After a few days, the leaves from both plants are tested for the presence of starch.
Observations:

Presence of Observation for the
Leaf Inference
carbon dioxide test for starch
Photosynthesis does not take place in the
Plant M No No change
absence of carbon dioxide.
The leaf turns Photosynthesis takes place in the presence of
Plant N Yes
blue-black carbon dioxide.
Discussion:
1. No starch is formed in the leaf of plant M which is exposed to the air without carbon dioxide.
2. Potassium hydroxide solution absorbs carbon dioxide inside the bell jar.
Conclusion:
The hypothesis is accepted. Carbon dioxide is essential for photosynthesis.

Eksperimen 2.1
Experiment 2.3
Eksperimen 2.1
Problem statement: Does photosynthesis require chlorophyll?
Hypothesis: Chlorophyll is essential for photosynthesis.
Aim: To investigate whether chlorophyll is essential for photosynthesis.
Manipulated variable: Presence of chlorophyll
Responding variable: Colour change of iodine on the leaf
Constant variable: Type of plants
Materials and apparatus: A variegated leaf, beaker, boiling tube, white
tile, Bunsen burner, tripod stand, wire gauze, forceps, dropper, ethanol, hot
water and iodine solution.
Procedure:
1. A variegated leaf is plucked from a plant which has been exposed to
the sunlight for several hours.
2. A sketch to show the green and non-green colour distributions on the
leaf is drawn.
3. The leaf is tested for the presence of starch. Figure 2.20 Variegated leaves
4. The observations are recorded.

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