Variables
-
Concentration of Sodium Chloride (NaCl) dependant variable
- Distance between electrodes
- Surface area of electrodes
-
Current independent variable
Apparatus
- Sodium Chloride (NaCl)
- Beaker
- Measuring cylinder
- Weighing boat
- Weighing scales
- Electrode x2
- Spatula
- Connecting wires
- Battery pack
- Ammeter
Safety Precautions
- I must ensure the power supply is turned off whilst connecting the wires to the ammeter and battery pack as electricity is highly dangerous.
- I must ensure I wear safety goggles during the experiment because the solution could become vigorous and begin to ‘spit’, so I would need to protect my eyes fromt his.
Preliminary testing
My target in the preliminary test was to familiarise myself with this experiment. I also needed to discover the volume of water I would need to use during my experiment and also what distance the electrodes would be apart, as these could affect my results. Also I would need to see what concentration of NaCl I would use for each test.
During this testing I decided to use 60ml of water, as this was jus over half the beaker’s volume and so it would not be hazardous and I would not spill anything from this, whereas if it was perhaps 70 or 80ml of water it could perhaps spill out whilst I stir the solution. I also decided to keep the electrodes 2cm apart. I also decided to add 0.25g of NaCl for each test, because a concentration of 0.1g would leave the results too close together and a concentration of 0.5g would cause the NaCl to take too long to dissolve and would leave the results too far apart.
Method
- To obtain an average set of results and to make it a fair test, I will carry out 3 results per concentration of Sodium Chloride (NaCl). This will hopefully ensure I do not obtain any anomalous results
- I will start by measuring 60ml of water in the measuring cylinder and pouring this into the beaker.
- Next I will measure the desired concentration of Sodium Chloride, starting at 0.25g and increasing it by 0.25g for each test until it amounts to 2g, using the weighing boat and the weighing scales. I will need to measure the mass of the weighing boat first in order to get the mass of the NaCl whilst it is in the boat.
- While doing this I will put the 2 electrodes in the water and ensure they are 2cm apart
- I will then put in the desired concentration of NaCl and stir until it has dissolved.
- I will then connect the circuit by attaching the ammeter to the connecting wires and the battery pack and then attaching the connecting wire to each electrode. I will then turn the battery pack on by the plug.
- I will then check the reading on the ammeter and record the results.
- After each experiment, I will wash out the beaker and repeat each test, obtaining 3 results per amount of NaCl.
Fair Test
To keep this experiment fair I will need to keep the voltage the same and the volume of water constant – 60ml, because too much will dilute the solution. I will obviously need to change the concentration of Sodium Chloride in order to do the test. I also need to keep the electrodes the same distance apart during each test as their distance apart will affect the results I obtain – 2cm apart and make sure I use the same electrodes throughout the experiment.
Diagram
Observation
Results Table
0.30 = anomalous result
Conclusion
I have found out that as the concentration of Sodium Chloride (NaCl) increase, the current increases also.
This conclusion can be support by the scientific knowledge provided in my hypothesis and also my prediction that the current and concentration are proportional; electricity is the free-flow of electrons (or charged particles) and therefore if there are an increased amount of electrons or charged particles by increasing the concentration of NaCl, then there will also be an increase in the current. This can also be supported in the results I obtained both in my table and more noticeably in my graph, as the line of best fit shows a positive gradient. I am happy with most of my results however I did obtain one anomalous result.
Evaluation
My plan and the results I obtained was very successful, as most of the results were close, if not on the line of best fit. I think it was successful as I had scientific knowledge and a strong prediction that enabled me to support and gain the results I expected.
However, I did obtain one anomalous result which has been highlighted both in the table and on the graph. I think I obtained this result because the electrodes were perhaps slightly further apart than desired, therefore the result was not near the line of best fit.
Other than this I obtained a good set of results as I kept the experiment a fair test. The volume of water used was kept constant, at 60ml and 0.25g of NaCl was added for each test. I collected three results per mass of NaCl as this enabled me to get fair and reliable results. With the exception of one anomalous result I obtained, the distance between the electrodes was kept 2cm apart.
This experimental method was suitable as it was quick and efficient, only lasting 3 lessons.
If I were to do this experiment again, I would ensure I would keep the test entirely fair by ensuring I keep the electrodes the same distance apart at all times, and concentrate harder in order to do so. Also if I were to suggest an alternative mean of doing this experiment, I could collect the amount of gas produced in 1 minute.
