My hypothesis is that when putting a penny in the vinegar instead of baking soda for about 5 minutes it well remain change its surface color. It will look cleaner because vinegar has alcoholic in it. It is also a cleaning product for almost everywhere in your house. It maybe a good cleaning product for the tarnished pennies. But in coco-cola the phosphoric and acid in soda removes the oxide coat and leaves the metal fresh and shiny. The reason it’s bright and shiny is its exposure to oxygen. In the presence of the moisture and salts, it will cover the dull oxide coat. the best option is cleaning the coins in, Vinegar. I think vinegar because when the acetic acid in turn, it also causes a chemical reaction, effectively removing the
