A student combines two liquids in a beaker. She observes that the mass of the combined liquid is less than the mass of the two separate liquids. The student claims that this observation shows that matter is not conserved in chemical reactions. Which statement explains why the student’s claim is incorrect?

The student's claim is incorrect because mass conservation in a closed system states that the total mass of substances before a reaction should equal the total mass of substances after the reaction, provided no matter is lost to the environment. In this case, the combined liquids may have resulted in some gas being released or evaporated during the mixing process, or there could be other external factors (like spillage) that caused a loss of mass. Therefore, the observation that the mass is less than the sum of the two liquids does not violate the principle of conservation of mass; rather, it suggests that some of the matter might have escaped from the beaker. In a closed and controlled environment, matter is always conserved in chemical reactions.