During the initial phase of designing, a basic model for a cell was decided upon. This basic model was based off of the Galvanic Cell but without any specific components. It simply included metal A, solution A, metal B, solution B, a salt bridge with solution C, and wires connecting the two half cells to the wire.
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To decide on these components, the virtual and physical labs, and activity series, and knowledge of E-waste were taken into consideration. It was initially decided that Copper metal and Aluminum metal would be used. That combination was a compromise between accessibility/safety and voltage potential. Aluminum is 'fairly high' on the activity series, and copper is 'fairly low' on the activity series. This would suggest that together they would produce a high voltage potential. Aluminum was never used in the labs, but the activity series showed low oxidation tendencies, which suggests high reduction tendencies. When this hypothesis was compared to a standard reduction potential table, the table depicted that the possible voltage potential would be 2.0V.
From this it was decided that the anode would be Aluminum metal placed in a solution of AlCl3, the cathode would be Copper placed in CuCl2, and the salt bridge would be NaCl solution (NaCl is common table salt, and it is very safe and accessible). This basic design was then used in the prototyping phase.
Our prototyping process required a significant amount of trial and error because we were getting lower voltages than expected (based on theoretical calculations). We tried to eliminate this error by polishing the electrodes with steel wool (to remove pieces of metal that were already oxidized) and replacing the electrodes with fresh ones every few trials. We also used copper wires (something not explicitly accounted for in many battery designs) and multiple pieces of filter paper (the salt bridges) to connect three cells in series. This was expected to increase the voltage a good deal from a single full cell battery.
From here we attempted to build a battery using Copper as the cathode and Aluminum as the anode, with a salt bridge containing salt water (NaCl). This gave us approximately 1.09 Volts. Then we realized that the Aluminum was not pure and was interfering with our electric current. Therefore we replaced the Aluminum with Zinc and tried running the battery again, amazed to reach 1.51 Volts.
A stage of inquiry followed our failure. As always, there was the possibility of forgetting to attach one of the electrodes, or the electrodes were too oxidized to produce the expected current. Therefore, we tried to switch our salt bridge solution from salt water to aqueous Magnesium Nitrate, hoping it would give a difference. The voltage with this battery was roughly 1.60 Volts, and our second attempt at powering the calculator was successful immediately after, so our battery design was finalized right there. Below are some photographs to document our success.
Our early prototype which didn't end up producing enough voltage to power our calculator
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