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Different amount of oxygen and carbon dioxide between Limnophilia Sessiliflora and Egeria dense
Introduction Nyborg Gymnasium
Plants are vital to our world; they have many benefits in our life, I am interested in plants and how much
is the amount of oxygen is produced, and amount of CO2 taken by them per gram. However, I would like
to interfere chemistry with biology, and I will do it using the ratio of the photosynthesis equation, so I
can obtain experimental values and compare it to the theoretical values. Hence, the experiment is
interesting, but it will be many control variables to consider which is not easy to work with, there is no
risk on the health as I am only using plants and water. I am using Egeria dense because we worked with
it before in an open system and I got encouraged to do my experiment in a closed system, the other
type of the plant is Limnophilia which we never worked with it before. Hence, they were available for
the experiment.
Research question
What is the difference between Limnophilia Sessiliflora and Egeria dense, (Elodea) of the amount of
oxygen produces per gram and the amount of carbon dioxide used, while measuring, the light intensity,
and having a constant temperature in the closed system?
Hypothesis
The most weighted plant the higher the amount of oxygen that will be produced, owing to there will be
a more significant amount of photosynthesis taking place in the plant which will release a higher amount
of oxygen.
Background information
Photosynthesis: converts the light energy from the sun to chemical energy that the plants use to build
sugar. However, it is complex reactions which consist of two different reactions: light-independent
reaction, and light-dependent reaction, (Refers to Brenda Walpole Biology for the IB Diploma second
edition page 82, and 85).
The mechanism of the light-dependent reaction occurs as the following:
Once a pair is excited electrons has been donated from PSII, no more electrons can be donated until the
holes are refilled. Then the electrons to refill the holes comes from the water, the reaction Centre
chlorophylls together with an enzyme split water; this is called photolysis. After that, each water
molecule releases two electrons, an oxygen atom, and two protons. This occurs inside the thylakoid
membrane. Then, the electrons are passed to the reaction Centre chlorophylls; protons are added to the
proton gradient and reduce NADP+, oxygen atoms from oxygen molecules. (Refer to page Brenda
Walpole Biology for the IB Diploma second edition 277, and 278).
Three factors are affecting the rate of photosynthesis: which are temperature, light intensity, and
carbon dioxide concentration they all factors that may affect the rate of photosynthesis. However, the
rate of photosynthesis cannot increase beyond a certain amount. For instance, glimpsing the
temperature to 30 C instead of 25 will increase the number of frequency collisions between the particles
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which will lead to increase the rate of photosynthesis. Hence, increasing the light intensity will increase
the rate of photosynthesis, but it will be limited at a certain point because the enzymes will be working
at their maximum rate. As well as, the CO2 concentration will lead to a higher rate if it increased
because it is crucial in the photosynthesis reaction to produce oxygen and sugar. Moreover, these
factors are a rationale for the crops inside the glass house for better productivity. Refer to page Brenda
Walpole Biology for the IB Diploma second edition 86 and 87).
Variables:
Independent variable
Depending variable
Control variable
The two species of the
plants.
The amount of oxygen
produced, and the
amount of carbon
dioxide taken by the
plants.
Temperature and the
saturation will be
measured using the same
machine that will allocate
the amount of oxygen in
the beaker.
The amount of water will
be measured using a 250
ml measuring cylinder at
the end of the experiment.
Control variable
Control variable
The speed was 200 ms
-1
.To
control the speed of the
magnet.
The plants must be
inside the water all the
time.
Considering the green
parts of the plant to
get a higher amount of
photosynthesis.
PH will be measured at the
beginning and the ending
of the experiment, and the
light intensity only once.
Materials
Ruler 30 cm ± 0.5 ,One Egeria dense (Elodea plant), magnetic stirrer, cylinder glass, deionized water
Scissors, Oxygen electrode, A machine to measure the light intensity, coverage, 2 lamps, PH meter,
electronic balance ±0.01g, and 1 Limnophilia Sessiliflora plant.
Procedure:
1. Cut 3 small piece of the Egeria dense (Elodia plant) by using the scissors and use the ruler to measure
15 cm of each of them, then add the 15 cm elodeas plant into the cylinder glass.
2. Add the magnet into the glass cylinder, pour deionized water gently to avoid the formation of
bubbles inside the cylinder glass.
4. Set the cylinder glass on the magnetic stirrer (Not the heat) and measure the PH of the water inside
the glass.
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5. Cover the top of the cylinder glass and press the on button. note: (make sure that the magnet is not
touching the plant will moving).
6. Add the Oxygen electrode into the cylinder glass by putting it in the appropriate place.
7. Turn on the light of the two lamps to let the photosynthesis takes place inside the glass and measure
the amount of light intensity using a machine to determine the amount of light emitted from the two
lamps.
8. Measure the oxygen every three mins for 15 mins using the oxygen electrode, remember to write the
temperature while measuring the oxygen using the same machine.
9. Repeat steps 1 to 8 five times to get adequate data. Measure the PH of water inside the glass at the
end of the experiment.
10. measure the amount of water that been used in the cylinder glass into a 250 ml measuring cylinder to
allocate the amount of water that has been used. Note: take the plants out of glass cylinder.
11.Redo the same experiment with the same steps from 1 to 9 using Limnophilia Sessiliflora plant.
12. Let the plants dry and the weight them using electronic balance.
Control experiment
1. Add the magnet into the cylinder glass, pour water gently to avoid the formation of bubbles inside
the cylinder glass, and Set the cylinder glass on the magnetic stirrer (Not the heat).
3. Cover the top of the cylinder glass and press the on the button, Add the Oxygen electrode into the
cylinder glass by putting it in the appropriate place.
5. measure the oxygen inside the closed system for 15 mins, every 3 mins, and write it down.
Set up of the Egeria dense (Elodea plant)
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