An Experiment to test which combinations of metals will produce the highest voltage in a variety of fruits to make a fruit battery Aim: To test which combinations of metals will produce the highest voltage in a fruit battery. Prediction: I predict that the combination of the most reactive metal (Magnesium) and the least reactive (Copper) in the fruit or electrolyte with the highest pH (grapefruit) will produce the highest voltage. Safety: There is always a concern when using electricity and acids about the safety.
Therefore I think it will be important to perhaps use gloves and goggles. Also, the experiment will be conducted whilst standing. Apparatus: Two 8 cm long strips each of magnesium ribbon, zinc foil, lead foil, copper foil and iron foil. A lemon, apple, potato and grapefruit, each with two holes cut in the top, 2 cm apart. Crocodile clips and wires. Digital voltmeter. Fair Test: I will keep this a fair test by only changing the variables (the fruit and metal combinations). I will use similar sized fruit and try to keep the surface area of each metal strip as similar as possible.
I must also ensure the holes in the fruit are accurately 2 cm apart and parallel to increase the accuracy of my results. Method: 8 cm long strips of magnesium, zinc, copper, lead and iron were cut out. Combinations of various metal strips were placed into a chosen fruit (lemon, apple, grapefruit or potato). A circuit was made using crocodile clips attached to the metal strips and a digital voltmeter. The voltage produced was observed on the digital voltmeter and recorded in a table.
This process was repeated until the four fruits had been tested. Diagram: Results: Pb – lead Cu – copper Mg – magnesium Zn – zinc Fe – iron The numbers in the table represent the amount of voltage or potential difference that was created. Lemon Pb Cu Mg Zn Analysis of results: The bar graph result shows clearly that the highest potential difference was produced with the combination of Magnesium and Copper in the grapefruit, producing an average of 1. 8 V.
This confirms my initial prediction, where I stated that a combination of the most reactive and least reactive metal would produce the greatest potential difference. Scientifically, this is de to the reactivity series, oxidation and reduction, and is shown in the electrochemical series. Redox reactions occur more commonly when a reductant and oxidant are placed in direct contact, like Magnesium in copper sulphate solution. In galvanic cells however, they are spaced apart and placed in some form of electrolyte, in this case, a fruit. A conducting external circuit connects them.
Let’s assume the electrodes are Magnesium and Copper. Magnesium is a strong reducing agent. Electrons from the copper become free as the magnesium indirectly reacts with the copper through the external conducting material. The electrons move through the conductor to the copper cathode. A reaction takes place at the anode and the magnesium is oxidised: Mg(s) Mg 2+ (aq) + 2 e- These extra electrons are now transferred through the conducting circuit, creating a voltage. The amount of voltage is determined by the potential energies of the reductant and the oxidant.