In a closed system, no matter can get in or out, so the mass stays the same.
In an open system, matter can get in or out, so the mass can change if that happens.
Density and flammability are properties.
In high concentrations, gases that are non-flammable with extinguish (put out) a flame.
Substances have properties that can help us identify them.
Properties do NOT change for a substance.
Gases or liquids that are less dense float upward when surrounded by gases or liquids that are more dense.
Gases or liquids that are more dense sink downward when surrounded by gases or liquids that are less dense.
The gases from the bath bomb could be carbon dioxide, nitrogen, or argon.
When a new substances are produced from old substances, some of the particles that made up the original substances break apart and/or join together to make new substances (particles).