Final answer:
The mass of a baggie after a chemical change should remain constant due to the Law of Conservation of Mass, which states that mass is conserved in a chemical reaction. Chemical changes merely rearrange atoms, without creating or destroying matter.
Step-by-step explanation:
The mass of the baggie after the chemical change is expected to be the same as it was before mixing the chemicals because of the Law of Conservation of Mass. This law states that mass is neither created nor destroyed in a chemical reaction. Therefore, the total mass we start with should be equal to the total mass we end up with. Chemical changes involve a rearrangement of atoms, and in all chemical processes, we cannot create or destroy matter – if we begin with a certain number of carbon atoms, for instance, we expect to have the same number of carbon atoms after the reaction.
Practical experiments like burning magnesium metal with oxygen to form magnesium oxide confirm this law, as the total mass remains unchanged before and after the reaction in a sealed environment. Even when bread dough is baked or magnesium is burned in air to form magnesium oxide, the mass doesn't increase or decrease – the matter simply changes form.