Photosynthesis is the process where a plant converts sunlight into glucose.
Glucose is the food for the plant, thus plants create there own food.
Plants do this by a chemical reaction. Plants use the sunlight, carbon
dioxide and water; plants use a chemical named chlorophyll in
photosynthesis. Chlorophyll is used to convert the sunlight into glucose.
There are two bi-products of this reaction; they are glucose, which is
useful to the plant as it is what the plant lives off, and oxygen, which is
not useful to the plant as a result of this it is released into the
The word equation of photosynthesis is:Order now
Carbon-dioxide + water >sunlight> glucose + oxygen
6CO2 + H2O >sunlight> C6H12O6 + 6O2
From the equation an easy way to measure the rate of photosynthesis is to
count the individual oxygen bubbles given off per unit of time e.g. bubbles
The apparatus that was used for this experiment was: beaker, boiling tube,
pond weed, lamp, water, meter ruler, stop clock scissors.
I predict that the closer the lamp to the boiling tube containing the pond
weed and water the faster the rate of photosynthesis, the more bubbles will
come from the weed and faster or larger.
The plant in the first and second
minute may be in a state of ‘warming up’ therefore the first and second
minute s results may be discarded these results are obtrusive.
Firstly the pond weed has to be prepared for the investigation. To do this
the bottom three to four rows of leaves must be removed using scissors. An
incision must then be made cutting diagonally at a 45? angle to allow the
bubbles to flow more freely from the stem of the plant.
The pond weed must be around seven centimeters in length and should also be
placed fully submerged in the boiling tube wit the end with the incision in
at the top of the boiling tube. The boiling tube should then be submerged
in water inside the beaker, this is done in order to make the experiment
fair as it makes sure that the outside temperature cannot affect the
results, and the radiated heat from the lamp may heat the water thus making
the experiment unfair.
The next thing that needs to be done is the meter
ruler needs to be placed next to the beaker and intervals of five
centimeters are marked on. The lamp is then placed at the first five
centimeters from the beaker the lamp is then switched on and pointing
toward the beaker.
The stop clock is started for a minute then stopped, during this minute the
amount of bubbles that come out of the stem of the plant are counted and
recorded in a results table. After the minute is over the lamp is moved to
the next five centimeter mark, it should be the ten cm mark, the stop watch
is started for a minute then stopped, and again the bubbles are counted and
recorded for that minute. This cycle continues until the lamp reaches the
|Minutes> |1 |2 |3 |4 |5 |Average |
|Stagesv | | | | | | |
|S1 5cm |15 |19 |26 |25 |23 |21.
| | | | | | |bubbles |
|S2 10cm |20 |22 |19 |17 |18 |19.2 |
| | | | | | |bubbles |
|S315cm |12 |11 |15 |14 |14 |8.8 bubbles|
|S4 20cm |12 |8 |5 |7 |12 |8.8 bubbles|
|S5 25cm |10 |5 |4 |6 |3 |5.6 bubbles|
|S6 30cm |2 |6 |1 |3 |2 |2.8 bubbles|
From the graph it is easy to determine that it agrees with my prediction.
The curved line of best fit shows how the photosynthesis rate of
From my graph I can see that the amount of light is not directly
proportionate to the rate of photosynthesis, I can say this because the
line in the graph is curved and not straight. There are no anomalous
results. To take this experiment further I could use color light filters to
see if the color of the light affects photosynthesis and the rate of
photosynthesis, then record the results and compare them to the results I
have already got. .