It's like this Paul. The rearrangement of atoms happen when the products are formed. For the products to form, there will be rearrangement of atoms. I't true that the atoms rearrange themselves when a reaction occurs. The same kinds and number of atoms that reacted are the same kinds and number if atoms that will be composing the product. In a chemical reaction, since there is a new substance formed, the atoms of the reacting species just rearranged themselves to produce them. Not a single atom is lost after a chemical reaction. With the blowing up of the earth, some things may vanish. But it does not mean that the atoms composing those vanished materials are also lost. They are just there, but rearranged to form the new products. These products may be in the form of gases. Maybe in the form of ash. Physical changes do not produce new products. An example is the dissolution of salt in water. The salt will just dissolve but its crystalline form can still be recovered through evaporation.
