Briefly explain why an unbalanced chemical equation cannot fully describe a reaction?

From the conservation of mass, matter is not created nor destroyed. So ponder it this way, for example I put one piece of toast in a toaster, but when it is done I had two pieces, that makes no sense right? Same thing with a chemical reaction but in molecular terms, all things must stay constant. If you put a convinced amount you have to get that quantity back, not less or not more in broad terms.

the ozone layer acts as a filter for the shorter wavelength and highly hazardous ultraviolet radiation (uvr) from the sun, protecting life on earth from its potentially harmful effects. when the sky is clear, there is an inverse relationship between stratospheric ozone and solar uvr measured at the earth's surface.