I have often tried to use the baking soda and vinegar lab as a way for my students to prove the law of conservation of mass/matter. I have never been successful in having the before and after mass be the same. It has alway been less by at least a gram. This is despite sealing with tape, double bagging it etc. The only explanation I have read is that the buoyancy of air surrounding the inflated balloon or bag has more affect on the products due to the increase in surface area. Can anyone give me a definitive answer and a resource to support this conclusion.
Thanks for your help. A frustrated middle school teacher!