Activity 6.11
Title
Objective
Problem Statement
Hypothesis
Variables
Manipulated
variable
Responding
variable
Fixed variable
Materials and
Apparatus
Technique
Procedure
Investigating the effect of light intensity on the rate of photosynthesis.
To investigate the effect of light intensity on the rate of
photosynthesis.
What is the effect of light intensity on the rate of photosynthesis?
The higher the light intensity, the higher the rate of photosynthesis.
Distance between light source and plant
Number of bubbles released in five minutes
Type of plant / Concentration of sodium hydrogen carbonate solution /
voltage of bulb
A few sprigs of Hydrilla sp., 1% sodium hydrogen carbonate solution,
distilled water and plasticine, 60 W bulb, 500 ml beaker, a test tube, a
glass funnel, a stopwatch, a thermometer and a meter ruler.
Count and record the number of bubbles released in five minutes.
1.
2.
3.
4.
Results
Graph:
Discussion:
Set up the apparatus as shown above.
Place the cut end of Hydrilla sp. stem facing upwards.
Put a table lamp 10 cm away from the beaker and switch it on.
When the rate of bubbles given out is constant, make five minute
bubble count.
5. Repeat steps 3 and 4 by putting the table lamp at different
distances of 20 cm, 30 cm, 40 cm and 50 cm from the beaker.
6. Record your results.
7. Plot a graph of number of bubbles produced against distance of
the light source from the beaker.
Distance of
the light
10
20
30
40
50
source (cm)
Number of
gas bubbles
produced in
five minute
(based on your data)
1. Explain how you control all the variables in this experiment?
Manipulated variable is distance of Hydrilla sp from the light
source. By ensure put the ruler close to the table lamp and
hydrilla sp.
Responding variable is number of gas bubbles released in five
minutes. By counting all bubbles with three observers in five
minutes.
Fix variable is type of plant. By using same type of Hydrilla sp.
2. Why is sodium hydrogen carbonate solution used instead of
distilled water?
Sodium hydrogen carbonate solution supplies carbon dioxide
needed by the plant to carry out photosynthesis.
3. How do you measure the rate of photosynthesis in Hydrilla sp.?
By counting the number of gas bubbles released in five minutes.
4. What do the following represent?
a. The number of bubbles released within a fixed period of
time
Rate of photosynthesis
b. The distance between the light source and the plant
Light intensity
Conclusion
5. Based on the graph, what inference can you make about the effect
of light intensity on the rate of photosynthesis?
The light intensity increase, the rate of photosynthesis increase.
The higher the light intensity, the higher the rate of photosynthesis.
Hypothesis is accepted.