2010 Biology Trial Paper 3, Question 2

Design an experiment to determine the effect of carbon dioxide concentration on the rate of photosynthesis.

Answer

Aim/objective:
To determine the effect of carbon dioxide concentration on the rate of photosynthesis.

Problem statement :
What is the effect of carbon dioxide concentration on the rate of photosynthesis?

Hypothesis
When the concentration of carbon dioxide increases, the rate of photosynthesis also increases until the rate becomes constant.

Variables
Manipulated : Concentration of carbon dioxide
Responding : The rate of photosynthesis// The number of bubble released per minute
Constant : Light intensity, temperature/ Size of plant

Apparatus and materials :
Materials : Elodea/Hydrilla , different concentration of sodium bicarbonate, distilled water
Apparatus : Beaker, boiling tube, clip, table lamp, filter funnel

Technique :
Count and record the number of bubbles produced / released in 20 minutes using a stopwatch .

Procedure :
1.Diagram of experimental setup with at least 5 functional labels.
2.Fill a boiling tube with 150 ml of 1% sodium hydrogen carbonate solution.
3.Fix a paper clip / plasticine to a sprig of aquatic / Hydrilla sp. plant.
4.Submerge / put the aquatic plant into the boiling tube containing 1% sodium hydrogen carbonate solution.
5.Put the boiling tube into a water bath at room temperature (20-30^oC).
6.Place the boiling tube at distance of 50 cm from a lighted bulb.
7.Put aside the boiling tube for 5 minute (for the aquatic plant to adjust).
8.Start the stopwatch.
9.Count the number of bubbles release in 20 minutes.
10.Record the result is a table.
11.Repeat steps 2 until 10 using 2%, 3% and 4% of sodium hydrogen carbonate solutions.
12.Calculate the rate of photosynthesis.
(Rate of photosynthesis = Number of bubbles/time)
13.Precaution : Count the bubbles only after the rate becomes constant.

Data
Include the following titles with units:
-Concentration of sodium hydrogen carbonates solution (%)
-Number of bubbles released in 20 minutes
-Rate of photosynthesis (number / minute)

Conclusion:
When the concentration of carbon dioxide increases, the rate of photosynthesis also increases until the rate becomes constant. Hypothesis is accepted.