• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

determine the relationship between potential diference and rate of photosynthesis

Free essay example:



Background information

We have read some article on the internet regarding the ‘relationship between electrical conductivity and ions present’. Here is some abstract from the internet article: ‘……however the difference in times of occurrence of the maxima of the polar conductivity and various ions concentrations indicate that all ions of different categories may contribute to polar conductivity in varying degrees’(source from the internet www.agn.org/pubs/crossref/1992/92JD01915.shtml ) hence our project is aimed at relating the ions present with the environment using a physics approach.


To find the conductivity of pond water and its relationship with the presence of ion.


The higher the potential difference of the pond water the more ions present.





The potential difference of pond water

Pond water from different parts of Singapore

Volume of sampled water used

Resistivity of wires used (in multi-meter)

Equipment and apparatus


8) Water samples from different parts of   Singapore

2) Cables

9) Distilled water

3) 4 x  200mlbeakers

4) Glass flask

5) Measuring cylinder

6) Pipette

7) Mass balance



1) Use the measuring cylinder to collect 150 ml of the pond water and put it separate glass beaker

2) Label the glass beaker respectively

3) Take the multimeter and adjust it to 2V DC mode

4) Immerse the electrodes into the pond water and record the readings

5) Repeat step 4 and take several readings

6) Ensure that the depth and the distance between the electrodes remain constant every time reading is taken

7) Use pipette to take 20.0 ml of the pond water sample

8) Measure the mass of the conical flask

9) Measure the mass of the conical flask after the addition of sample pond water

10) Record the data obtained

11) Show relationship between density and conductivity

Data collection

Table of potential difference of collected sample of pond water

Location of water sample

1st reading ± 0.001/V

2nd reading ± 0.001/V

3rd reading± 0.001/V

Average potential difference ± 0.001/V

De-ionized water





NUS Prince George Park pond





ACS(I) pond





Bukit Timah nature reserve





Botanical Garden swan






Table of mass of pond water

Location  of water sample

Volume of pond water ± 0.06/cm3

Mass of conical flask ± 0.01/ g

Mass of conical flask + pond water ± 0.01/ g

Mass of pond water ± 0.01/ g

ACS(I) pond water





Botanical Garden pond water





NUS pond water





Bukit Timah nature reserve





De-ionized water







Density of ACS (I) water= mass/volume

                            = 20.23/20.0

                                        = 1.012 g/cm3

Density of NUS pond water= mass/volume

                                = 20.21/20.0

                                            = 1.011 g/cm3

Density of Botanical garden pond water= mass/volume

                                           = 20.18/20.0

                                                                = 1.009 g/cm3

Density of Bukit Timah pond water= mass/volume

                                         = 20.16/20.0

                                                         = 1.008g/cm3

Density of de-ionized water= mass/volume

                                = 20.02/20.0

                                            = 1.001 g/cm3

Uncertainty – sample calculation

      Δρ         = (Δm/m + ΔV/V) x ρ

        = (0.01/20.23 + 0.06/20.0) x 1.0115

        = 0.003        

Table indicating relationship between density and potential difference

Location  of water sample

Density ρ ± 0.003 / gcm-3

Potential difference  ±  0.001/ V

NUS pond water



ACS(I) pond water



Botanical Garden pond water



Bukit Timah pond water



De-ionized water



Conclusion and evaluation

  • Percentage uncertainty=0.003/1.0115image00.png100%image01.pngimage00.png


  • Negligible uncertainty suggests that the experimental method is accurate. Since the presence of ions contributes to he conductivity of electricity, moreover based on the data and calculation, the higher the potential difference the higher the concentration of the ions present. The more ions present the denser the water is.

Our group’s biology student carried out another experiment, using Ervatamia leaf, with the help of hold punch, syringe, 18 watt lamp, and stopwatch; they found out that ACS (I) pond water has the fastest rate of photosynthesis. This can be linked to our physics part: the higher potential difference the faster the rate of photosynthesis. But this is not the case because ACS (I) pond water only has the second highest potential difference.

This shows that there are limitations and inaccuracy in the experimental method, though the percentage uncertainty suggests accurate method.

This may be due to the imprecise and uncertainty involved when the water and getting potential difference weigh.

  1. Water in the pipette may not be transferred completely into conical flask. However the volume used in calculation are all 20.0ml.
  2. When reading multimter the readings fluctuate a lot hence an average reading was taken for every set of reading. This is inaccurate since the potential difference changes though the variables are controlled. Furthermore, the readings of potential difference are directly compared with the density of the water; hence if the readings are inaccurate, the conclusion may not be correct either.


UV-VIS spectrometer could be used t test/measure what are the concentrations of ions present in the pond water so that a more accurate conclusion can be derived.


To be honest, including a portion of physics component was something which I did not even think about before the experiment was carried out; neither did I expect it to happen. The reason why we measure the density and potential difference of the sampled water was merely because we could not think of nay physics terms which we can measure for this experiment! Ironically these random trying became the inspiration which drove us to think further and out of the box. That was how we linked rate of photosynthesis to potential difference of sampled water.

However I am sure that there are uncertainties in our results and conclusion. Especially the potential difference of sampled water, (even the way we measured the potential difference was doubtful) which fluctuated a lot: the reading was decreasing and increasing all the time and for a very few seconds, it stayed constant. Hence the readings we recorded were actually the average value.

There are many things to learn apart from the physics component. Normally we can hardly find someone taking a biology and physics combination; however we almost successfully related physics to biology. I realize that design an experiment is so important that it really prove’ well begun half done’. It was really a memorable experience.

This student written piece of work is one of many that can be found in our GCSE Green Plants as Organisms section.

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Related GCSE Science Skills and Knowledge Essays

See our best essays

Related GCSE Green Plants as Organisms essays

  1. How temperature affects the rate of photosynthesis.

    correlation to the line of best fit not only for the personal results but also for the class averages. Similar trends shown by both graphs (with anomalies at the same temperature) show that any major drawbacks in the experiment affected the whole class and not only the individual results.

  2. Determine the water potential of potato tuber cell with the varying affect of solute ...

    This also turned out to be correct because I knew that since there is a higher concentration of solute molecules in the solution it means that now there is a lower concentration of water outside the cell which will mean that less water will go in the cell.

  1. Investigation into the relationship between the density of fresh water shrimps in fleet brook ...

    are broken down by denitrifying bacteria inhabiting the water. The nitrogenous molecules are converted into nitrates Nitrate and phosphates are regulators of organic growth. The free flowing algae and small planktonic forms are affected directly. High levels of nitrates and phosphates often stimulate their growth. Gammarus feed on these.

  2. Sensor Project

    Which the float arm would be at a different angle as more water is added as seen in the diagram. -Length of the float arm - this is a significant factor to the change in voltage of the potentiometer and the amount of movement.

  1. The location of panama

    The Pedro Miguel locks lower the ship 9.4 meters to a lake, which then takes it to the Miraflore locks. This lowers the ship 16metres to sea level at the canals pacific terminus in the bay of panama. Finally the canal carries the ship to the harbour where the canal pilot leaves the vessel.

  2. History of the ALP Project.

    Storage is a significant aspect of water supply in the semi-arid western United States, where there is usually not a dependable, regular flow of adequate water in streams and rivers to meet water requirements year round. Lastly, the project will provide practically 33% of the storage in Ridges Basin Reservoir for use by non-Indian entities in the Four Corners region.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work