Question

evelyn mixes vinegar and baking soda in a sealed container. after the reaction, she weighs the container and finds it has the same mass as before. what scientific law does this demonstrate?
mass is created in a chemical reaction
mass is created in a physical change
new chemicals formed from a chemical reaction have a larger overall mass than the original reactants
mass is never created or destroyed

Explanation:

The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction. In this case, Evelyn mixes vinegar and baking soda in a sealed container. Since the container is sealed, no mass can escape (as would happen if it were an open - container where gas could escape). The fact that the mass of the container and its contents after the reaction is the same as before the reaction shows that mass is not created (eliminating options like "Mass is created in a chemical reaction" and "Mass is created in a physical change") and not destroyed (eliminating "New chemicals formed from a chemical reaction have a larger overall mass than the original reactants").

Answer:

Mass is never created or destroyed.