When coal burn it leave ash behind. Ash so produced is lighter than the coal which has burnt. justify the decrease in mass in the light of law of conservation of mass?

When coal burns, it undergoes a chemical reaction with oxygen to produce heat, light, and various byproducts, including ash. The ash produced is lighter than the original coal because during the combustion process, some of the mass is converted into gases such as carbon dioxide and water vapor that are released into the atmosphere. This decrease in mass is in line with the law of conservation of mass, which states that mass cannot be created or destroyed in a chemical reaction, only rearranged. In this case, the mass of the coal is rearranged into lighter byproducts like gases and ash.