What is a pure substance that is present before a reaction but not after.

The mass has escaped into a gas which you can not see so the law stays true.

The atomic nucleus made up from protons (yellow) and neutrons (blue) and held together by nuclear forces. nuclear forces (also known as nuclear interactions or strong forces) are the forces that act between two or more nucleons. they bind protons and neutrons (“nucleons”) into atomic

Answer heart of american                  live in harmony                    hillsides of orchards                    blaze of color                    backdrop of pines;

Ibelieve the answer is weathering,hope my answer has you : )