Over the years, many interesting chemical reactions and activities have been used to illustrate the conservation of mass. The reaction of baking soda and vinegar is a common example. The experimental procedure described in this article presents a special case involving buoyancy where the buoyancy effect is exacerbated by the fact that the reaction container expands as the reaction proceeds and a large volume of air is displaced. The data reported here were gathered at a specific pressure and temperature using a certain type of balloon. Specific values will depend on temperature, barometric pressure, humidity, type of balloon, and the amounts of vinegar and baking soda. However, the relationship among variables should remain the same.