Suppose a lab reports the mass of the sand higher that it really is. Is it really possible to collect more sand than was originally present? What is a possible explanation for the extra product?

No, it's the law of conservation of mass. In a closed system, the amount of mass remains constant over time. In a chemical reaction the mass of the reactant will theoretically be equal to the mass of products.

possibly explanations:

· could be gross error (miscalculation?)

· or a chemical reaction producing more sand

· or there's something else mixed in with the sand.

last explanation is probably the most likely.