Is the process that changes the flavor of a banana a physical process?
As bananas ripen, their flavor changes and they become sweeter. This is due to the breaking down of their starches into sugars. Starches are actually polymers, or long chains, of simple sugars. Sugars are the monomers, or building blocks, of the starch polymers (mono- means one and poly- means many).
As bananas ripen, the bonds that hold the monomers together in the starch are hydrolyzed by enzymes (amylases). This means that when water is added to the bonds, the bonds break, releasing the monomer sugars (like glucose). These simple sugars give the fruit a much sweeter taste than starches.
This is a chemical rather than a physical change because bonds are being broken and the composition of the material is changing. With a physical change, the physical properties are changed, but the composition remains the same. An example of a physical change is the melting of ice; the water goes from being a solid to a liquid, but remains as water the entire time. As bananas ripen, the starches are being changed, with the breaking of bonds, into simple sugars, a chemical change.