Explain Conservation of Mass Practice Test

A candle is burned in an open system (in open air). The student measures only the candle and its holder.

Measurements:

• Before burning: 20 g
• After burning: 1 g (wax residue)

Which statement best explains why it seems like mass was lost?

A student compares a closed-system and open-system setup for the reaction of baking soda and vinegar.

Closed system (balloon attached): total mass before = 55 g, total mass after = 55 g.

Open system (no balloon; gas escapes): mass of flask + liquid before = 55 g, mass after = 51 g.

Which statement best describes what these results show?