Question

Think about "The Law of Conservation of Mass" (In a chemical change, the total mass of the new substances is always the same as the total mass of the original substances.) Why might it be difficult to demonstrate this law in chemical changes where one or more of the products is a gas?

Answer 1

The Law of Conservation of Mass states matter cannot be created/destroyed in a chemical reaction

It is hard to prove the law because the gas molecules move out the area quickly, at a higher speed than liquid or solid particles.

If their appears to be a loss in mass, it is because of the above, and that is why it may be difficult to demonstrate this 'law'.