Final answer:
Ash is the non-combustible residue left after a material like wood or coal has undergone complete combustion, in accordance with the Law of Conservation of Mass.
Step-by-step explanation:
Ash is the residue that remains after complete combustion has taken place. When a material like wood or coal burns, it reacts with oxygen, leading to a chemical process that produces ashes, carbon dioxide, and water vapor. The gases produced during combustion are released into the air, leaving behind the ash, which is primarily composed of inorganic matter such as metal oxides and other non-combustible substances. This phenomenon also illustrates the Law of Conservation of Mass, which states that the total mass of matter remains constant before and after a chemical reaction, like burning.