The iron and oxygen have ____________ to form ___________________ which is a __________ . It contains both ___________ and iron. The _______________ together with the remaining _________weigh _________ than at the start. The _________ increases because _________ the iron atoms are still in the solid. The reaction has added ___________ atoms to the solid. At the end of the reaction, there are _________atoms in the container than at the start.