Explain apparent changes in mass during reactions as being caused by reactants or products acting as a gas in non-enclosed systems.
Understand that reacting a solid with a gas (e.g., metals reacting with oxygen) can lead to an apparent increase in mass.
Understand that a reaction producing a gas that escapes into the atmosphere (e.g., thermal decomposition of metal carbonates) can lead to an apparent decrease in mass.
Analyze these observed changes in mass using the particle model and balanced symbol equations.
