G
Galvanic Cell Experiment: A common school experiment where an acidic fruit or vegetable, such as a lemon or potato, is used to demonstrate how a battery works. It involves converting chemical energy into electrical energy using a lemon (citric acid) or potato (phosphoric acid) and inserting two different metals as electrodes. The potential difference between the metals allows current to flow.
The electrodes used are usually a galvanised nail (i.e. zinc coated metal) and a copper penny. Copper is the positive electrode (cathode) and zinc is the negative electrode (anode). An electrochemical Redox reaction occurs. Zinc has a lower reduction potential than copper so it will be oxidised (lose electrons). The lemon / potato juice acts as an electrolyte allowing free movement of ions.
The acid in the lemon or potato contains H+ ions which are reduced to hydrogen gas in the reaction.
Zn → Zn2+ + 2e- (Oxidation)
2H+ + 2e- → H2 (Reduction)
If zinc and copper were connected by conductive wire in air; current would flow as a result of the difference in reduction potentials, with the zinc anode losing electrons to the copper cathode. This would continue until the force of repulsion, from the build up of electrons, equalled the force of attraction at the cathode.
However, when the electrodes are immersed in a conductive solution (lemon or potato), this is continuous (until the elements are consumed). So when the zinc and copper electrode are connected, using conductive wire, in a lemon / potato battery arrangement, the hydrogen ions are reduced at the copper cathode and a current is established in the conductive wire.
GCMS: Gas Chromatography Mass Spectroscopy. Technology combining gas chromatography and mass spectrometry that is used in the analysis of chemical substances.
Geodesic – Relating to the geometry of curved surfaces.
Geodetics (or geodesy) – A branch of earth sciences; concerned with determining the precise location of geographical points (e.g. depths of oceans or mountain peaks) and the shape and size of the Earth. Geodetics also includes the study of the Earth’s gravitational field, tides, crustal shifts and polar motion.
Geodesist – A person who studies or works in the field of geodetics.
Pending Update.
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