in this video we're going to talk about the law of conservation of mass so what is the main idea behind this law the main idea is that matter cannot be created or destroyed in a chemical reaction so let me give you an example let's say if we react methane gas with oxygen so let's say if we have a closed container and we're going to make 16 G of Meth in this container we're also going to place 64 G of oxygen gas so the methane and the oxygen gas they cannot leave the container they're stuck there now as the reaction proceeds it's a combustion reaction it's going to produce carbon dioxide and water vapor depending on the temperature now let's say if if you collect 44 G of carbon dioxide according to the law of conservation of mass how many G of water should you expect to be present at the end of this reaction now think of the total mass of the reactants the reactants are the stuff on the left side we have 16 G of methane and 64 G of oxygen so therefore we're starting with 80 g of reactants so before the reaction we had 80 g of matter at the end of the reaction according to the law of conservation of mass in a closed system you should still have 80 g of mass so if we have 44 G of carbon dioxide the remaining amount of mass should be water 80 - 44 is 36 so therefore we should back to collect 36 G of water and that's the main idea behind the law of conservation of mass if you have 80 g of material inside the closed container before the reaction then when the reaction is complete you should still have 80 g of matter inside that container in a chemical reaction the only thing that's happening is that the atoms are rearranging themselves here carbon is bonded to hydrogen but now it's Bond oxygen so therefore the total mass should remain the same the atoms are simply switching Partners they just rearrange themselves in this chemical reaction but the amount of mass the quantity of matter should still remain the same the only way you can change it is if you add more mass into the the chamber or the reaction container for