Editing Penny Alchemy (section)

===Short Explanation===

The pennies are being placed in a strong basic NaOH solution, which is being heated by the hot plate. ''Basic'' solutions can be thought of as the opposites of acids: they accept protons, add negative ions to a solution, and increase the pH of the solution. Acids accept electrons, add positive ions to a solution, and decrease the pH of the solution. Most soaps are weak bases, so one can think of our NaOH solution as being a really strong "soap". The copper on a penny can dissolve into a basic solution, but only if two things are met: The solution needs to be hot, and the copper needs to be in contact with the zinc in the beaker. The zinc in the bottom of the beaker can dissolve, but just barely. The zinc would rather take the place of the copper as it dissolves off the penny, so once the penny touches the zinc we see this happen! The penny starts bubbling rapidly, and in less than a minute the outside layer of copper has dissolved, with it's place taken by the zinc! This type of reaction is called a ''Single Displacement Reaction'', since a single element (Copper) switched places with another (Zinc).

The "silver" pennies have only a very thin layer of zinc on top of the copper underneath. These zinc-plated pennies can have their silver color rubbed off after repeated use, since the zinc is only sitting on top of the copper. When the zinc-plated pennies are heated up on the hot plate, the zinc layer and copper layer start to heat up together. This causes them to meld together, with the zinc atoms sliding between the copper atoms, and become brass! Brass is a ''Metal Alloy'', or a metal which comes from the combination of different metal elements. Brass is often used to make instruments such as tubas, trumpets and saxophones, and is recognized by its yellow-gold color.