Mass Stays the Same Practice Test

A student measures the mass of a closed system where a gas is produced and captured. The system mass is 200.0 g before the reaction and 199.9 g after the reaction. The balance uncertainty is ±0.1 g.

Does the data support conservation of mass? Choose the best answer.

A student measures a sealed (closed) container before and after a reaction that produces a noticeable temperature change. The mass is 75.3 g before and 75.3 g after.

Which statement best interprets this evidence?