Philip Smedegaard MYP5K Chemistry 02-12-2009
Electrolysis & Current Investigation
Introduction: Ohm’s law states, that any current passing through an object that conducts electricity, is directly affected by the voltage initially produced, and the amount of resistance in the conductivity. That means when measuring the conductivity of an object, several factors have to be considered to find the right amount of current produced: voltage initially produced, along with resistant factors. Georg Simon Ohm’s law is directly relevant to the process of electrolysis. Electrolysis is the process of using electricity to split up atoms to form a chemical reaction. In order for electrolysis to work, a solution along with a direct source of electricity is needed. In addition two probes known as electrodes are needed to conduct the electricity. Electrolysis along with Ohm’s law are used frequently, and it is an effective way of splitting up atoms by either adding or decreasing the number of electrons in the solution. I= current V= voltage R= resistance
AimThe aim of this experiment is to see how the factor of temperature, affects the current produced during electrolysis. HypothesisI predict that the more the temperature increases, the more current will be produced during electrolysis because; when solutions are heated the electrons start racing around everywhere, which will therefore make the solution less resistant. When there is less resistance it will be easier to conduct electricity, so therefore the higher the temperature the more current will be produced, because of the resistance factor. In Ohm’s law the resistance factor also plays a key role on the current produced, and in this case, the temperature will affect the resistance. VariablesIndependent variable Temperature of solution (°C) (sodium chloride)
Dependant variable The current produced (Amps)
Controlled variable Concentration of solution Distance between electrodes Type of electrodes
Volume of solution Depth of electrodes Voltage Independent variableWhat we are changing in order to affect the resistance in Ohm’s law is the temperature. The way seeing how temperature affects the current produced, is by having four different temperatures and seeing how many Amps are produced for each temperature. The way we are regulating and controlling the temperature, is by using water baths which automatically keep the temperature constant. Dependant variableWhat we are measuring, is the current produced during electrolysis. The way we are measuring the current produced, is through an ammeter which will show the current produced in amps. Controlled variablesThere are many other variables to consider, which can have a large effect on the outcome of the experiment. Small details which can alter the current produced needs to be closely regulated, so that is why some of the controlled variables listed above will be kept constant in order to have a fair trial.
Procedure: Apparatus• • • • • • • • • • • • • • •
Thermometer 50ml measuring cylinder 4 x 50ml glass beakers 4 x 25ml of 10% sodium chloride Stand Clamp Ammeter Power box 3 wires 2 crocodile clips that can attach to wire 2 x 8cm graphite electrodes Electrode holder 2 water baths Ice cubes Stopwatch
Diagram of Apparatus-
Method1. Set up apparatus 2. In a large beaker (doesn’t matter what type) add tap-water plus ice cubes. Then place a 50ml glass beaker with the 25ml 10% sodium chloride solution, into the large “iced” beaker to cool the solution. 3. Wait until temperature of the sodium chloride reaches about 18°C 4. Then place electrodes into the sodium chloride solution, with a depth of 1cm, and a 2cm distance between each graphite electrode 5. Turn on the power box to 8 volts 6. Make sure the electrodes are not touching and the temperature is about 18°C 7. Then record how much current is produced in (Amps) 8. Wait 1 minute, and then record again the current produced in (Amps) 9. Get a new glass beaker with 25ml of fresh 10% sodium chloride, and wait until it turns room temperature (24°C) 10. Repeat steps #4-5 11. Record the current produced in (Amps) by looking at the ammeter 12. Wait 1 minute, and then record current produced again 13. In a new 50ml glass beaker, pour 25ml of fresh 10% sodium chloride into the beaker, and place beaker into the 62°C water bath
14. Wait until the sodium chloride is 62°C 15. Repeat steps #4-5 16. Then record current produced in (Amps) 17. Wait 1 minute and then record current produced again 18. In a new 50ml glass beaker, pour 25ml of fresh 10% sodium chloride into the beaker, and place beaker into a 82°C water bath 19. Wait until sodium chloride is 82°C 20. Repeat steps# 4-5 21. Then record current produced in (Amps) 22. Wait 1 minute and then record current produced again 23. Record and organize all data collected
Raw Data-
Trial 1Temperature (°C) 18 24 62 82
Current Produced (Amps) 0.2 0.4 0.6 0.7
Trial 2Temperature (°C)
Current Produced (Amps)
18 24 62 82
0.2 0.5 0.6 0.6
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For the investigation, 25ml of 10% sodium chloride was used for each temperature
•
For each trial 8 volts was used
Processed Data-
Calculations18°C- 0.2 + 0.2/ 2= 0.2 Amps 24°C- 0.4 + 0.5/ 2= 0.45 Amps 62°C- 0.6 + 0.6/2= 0.6 Amps 82°C- 0.6 + 0.7/2= 0.65 Amps
AveragesTemperature (°C) 18 24 62 82
Graph-
Current Produced (Amps) 0.2 0.45 0.6 0.65
Conclusion: Based on the data I collected, I can see that my hypothesis was supported, because as the temperature increased, so did the current produced. The reason why the current increases when the temperature rises, is because the resistance of the electrons decreases which allows for more electricity to be conducted. With many particles, when they are heated, they start to move around and spread out and the higher the temperature: the faster the electrons move around. When the electrons are moving fast around, the resistance factor (which is mentioned in Ohm’s law) decreases, and that is why the number of Amps increased. There weren’t really that many patterns in our data, because more varied temperatures would reveal more patterns. Therefore based on that theory by Ohm, and by the data that I collected, I can conclude that the higher the temperature, the more the current increases as well. Temperature is a factor that affects the current produced, and Ohm’s law can help calculate and predict how much the temperature will affect the current.
Evaluation: There were quite a lot of things to control and monitor in this investigation, because in order to get the right current, there were many variables that had to be controlled. Since there were so many factors that could change our results such as: a different volume of the solution, or the same voltage, or the depth of the electrodes: it was important to keep everything constant and organized. Our method proved to work quite well, because it showed reliable results that confirm parts of Ohm’s law, however there were some flaws that prevented the method from being 100% effective and convenient. Firstly, in order to get more data, it would have been smart if we had time to try more temperatures, because that could give us more data and patterns to work with. Secondly, the regulation of the electrodes was rather difficult because, in order to hold the electrodes we used a stand and a clamp. This held the electrodes in such a way, which made it very difficult to place both electrodes evenly into the glass beaker, because the clamp wasn’t very maneuverable, and that the circumference of the beaker was almost too small to fit the electrodes. To record the measurements for the current produced, we used an analog ammeter, which actually did make it a little hard to see exactly how many Amps were produced. For next time, I think it would be smarter to use a digital ammeter because it is easier to read during an investigation. We did repeat our investigation twice, in order to be able to find a solid average later on, but like in many investigations, you have to have many different trials in order to get the most reliable data. There wasn’t really that much anomalous data, because the temperature differences were fairly even, that is why the data increases rather smoothly. Another big factor that showed in my data was that in my temperatures, between 24°C and 62°C that is a rather large gap, which could have had an effect on my data. I do think that this was a fair investigation, as many things were kept constant and regulated, although there were a few variable which were difficult to control. E.g. distance between electrodes, etc. Some things that I would change if I was to do the investigation again are:
• Have more temperatures to measure • Better system for holding electrodes • Use a digital ammeter Overall, this investigation looked at what factors affect the current during electrolysis, and based on my data, I can say that temperature definitely has an effect on the current produced. Another example of an investigation like this could be to simply see how the voltage affects the current produced.
Things to remember in evaluation: • • • • • • • • •
Distance between electrodes Depth of electrodes Fresh solution Gap between 24-62 one more trial Larger beaker Use digital ammeter Type of beaker Next time use a beaker with bigger circumference to fit the electrode holder Diagram- 1 water bath for 62 and 82 °C and just a beaker