Photosynthesis Completion Practical
Added on 2023-03-17
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Photosynthesis Completion Practical:
Aim: To observe photosynthesis in a species of pondweed at different light intensities.
Introduction:
Plants are the most common autotrophs in the ecosystem as they are able to make their own food
by undergoing a process called photosynthesis. It is the process in which the plant transfers light
energy into chemical energy in the form of oxygen and glucose. This process takes place in the
chloroplastswhich are responsible for carrying out the reaction of photosynthesis (Khan
Academy, 2019) . Each chloroplastcontains a compartment called thylakoids. Each thylakoid
membrane contains chlorophyll that are green-colored pigments responsible for absorbing light
(Bassham and Lambers, 2019).
Chemical and word equation of photosynthesis:
Carbon dioxide + water → oxygen + glucose.
6CO2 + 6H2O > C6H12O6 + 6O2
(light energy)
Factors that affect the rate of photosynthesis are light intensity, temperature, the concentration of
carbon dioxide and water. Light is very crucial as it provides that energy required for plants to go
through photosynthesis. The rate of photosynthesis increases as the light intensity increases as
long as enough carbon dioxide and water are accessible. As aquatic plants photosynthesis, they
release bubbles of oxygen which is measured over a period of time then the rate of oxygen can
be determined.
In this experiment, the effect of light intensity on the rate of photosynthesis is investigated. A
torch is being used to determine the variety of light intensity alter the process of photosynthesis
in the pondweed.
Aim: To observe photosynthesis in a species of pondweed at different light intensities.
Introduction:
Plants are the most common autotrophs in the ecosystem as they are able to make their own food
by undergoing a process called photosynthesis. It is the process in which the plant transfers light
energy into chemical energy in the form of oxygen and glucose. This process takes place in the
chloroplastswhich are responsible for carrying out the reaction of photosynthesis (Khan
Academy, 2019) . Each chloroplastcontains a compartment called thylakoids. Each thylakoid
membrane contains chlorophyll that are green-colored pigments responsible for absorbing light
(Bassham and Lambers, 2019).
Chemical and word equation of photosynthesis:
Carbon dioxide + water → oxygen + glucose.
6CO2 + 6H2O > C6H12O6 + 6O2
(light energy)
Factors that affect the rate of photosynthesis are light intensity, temperature, the concentration of
carbon dioxide and water. Light is very crucial as it provides that energy required for plants to go
through photosynthesis. The rate of photosynthesis increases as the light intensity increases as
long as enough carbon dioxide and water are accessible. As aquatic plants photosynthesis, they
release bubbles of oxygen which is measured over a period of time then the rate of oxygen can
be determined.
In this experiment, the effect of light intensity on the rate of photosynthesis is investigated. A
torch is being used to determine the variety of light intensity alter the process of photosynthesis
in the pondweed.
Hypothesis:
If the distance of the torch increases then the amount of the oxygen bubbles will decrease.
Variables:
Independent variables:
- The distance between the light and the plant
Dependent variables:
- The number of bubbles formed over a limited period of time
Controlled:
- The amount of water in the beaker
- The length of the pondweed (hydrilla)
- The amount of hydrogen carbonate solution in the beaker (6%)
Variables that couldn’t be controlled:
- The temperature of the room
If the distance of the torch increases then the amount of the oxygen bubbles will decrease.
Variables:
Independent variables:
- The distance between the light and the plant
Dependent variables:
- The number of bubbles formed over a limited period of time
Controlled:
- The amount of water in the beaker
- The length of the pondweed (hydrilla)
- The amount of hydrogen carbonate solution in the beaker (6%)
Variables that couldn’t be controlled:
- The temperature of the room
Photosynthesis Completion Practical:
Materials:
Glass funnel Ruler
800ml beaker Sodium hydrogen carbonate solution (6%)
Light source (torch) Pondweed
Scissors Stopwatch
Method:
1) Cut two x 5cm pieces of pond weed using ruler and scissors.
2) Fill a large beaker with room temperature 6% sodium hydrogen carbonate solution.
3) Set up the apparatus as shown in the diagram below. Be sure to insert the pieces of
pond week into the funnel with the cut ends positioned upwards.
4) Have the torch placed 15cm away from the beaker, aimed directly at the pieces of
pondweed. Allow the pondweed to acclimatize to this light intensity for 2 minutes before
counting any bubbles.
5) Record the number of bubbles produced by the pondweed in 4 minutes period.
6) Replicate steps 1-5 three more times, but with torch distances of 10cm, 5cm and 2
cm. Ensure that a 2-minute period of acclimatization occurs before commencing the 4-minute
count.
7) Collaborate with another group to obtain data for the purposes of a 2nd trial.
8) Record data in a table, including the conversion from the distance to intensity.
Materials:
Glass funnel Ruler
800ml beaker Sodium hydrogen carbonate solution (6%)
Light source (torch) Pondweed
Scissors Stopwatch
Method:
1) Cut two x 5cm pieces of pond weed using ruler and scissors.
2) Fill a large beaker with room temperature 6% sodium hydrogen carbonate solution.
3) Set up the apparatus as shown in the diagram below. Be sure to insert the pieces of
pond week into the funnel with the cut ends positioned upwards.
4) Have the torch placed 15cm away from the beaker, aimed directly at the pieces of
pondweed. Allow the pondweed to acclimatize to this light intensity for 2 minutes before
counting any bubbles.
5) Record the number of bubbles produced by the pondweed in 4 minutes period.
6) Replicate steps 1-5 three more times, but with torch distances of 10cm, 5cm and 2
cm. Ensure that a 2-minute period of acclimatization occurs before commencing the 4-minute
count.
7) Collaborate with another group to obtain data for the purposes of a 2nd trial.
8) Record data in a table, including the conversion from the distance to intensity.
Safety:
The experiment had some safety and ethical risks and hazards such as the risk of breaking the
glass that was the beaker. It might fall and break if kept at the corner of the table that can lead to
cut. To avoid this, you must keep it at a safe place and if it breaks, ask for help from the teacher.
Another risk could be from the scissors while cutting the pondweed to its desired size.
Results:
Photosynthesis Completion Practical:
Light intensity
Distance ( Amount of bubbles produced in
cm) the funnel
Trial 1 Trial 2 Average
2cm 130 53 91.5
5cm 110 37 73.5
10cm 72 23 47.5
15cm 62 20 41
The experiment had some safety and ethical risks and hazards such as the risk of breaking the
glass that was the beaker. It might fall and break if kept at the corner of the table that can lead to
cut. To avoid this, you must keep it at a safe place and if it breaks, ask for help from the teacher.
Another risk could be from the scissors while cutting the pondweed to its desired size.
Results:
Photosynthesis Completion Practical:
Light intensity
Distance ( Amount of bubbles produced in
cm) the funnel
Trial 1 Trial 2 Average
2cm 130 53 91.5
5cm 110 37 73.5
10cm 72 23 47.5
15cm 62 20 41
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