Conservation of Matter

Track atoms, mass, and system boundaries

Mission: test a closed reaction

React vinegar and bicarbonate inside the sealed capsule. Compare measured mass before and after.

Experiment

System controls

Live mass accounting educational model

145.00 gbalance reading
145.00 gmatter incl. escaped
0.00 gescaped gas
0%process progress
Atoms before → afterEqual

Canvas graph key

Total matterBalance readingEscaped gas

The text-free graph compares matter inside the boundary with matter accounted for everywhere.

Molecule

Reactantrole
Insidelocation

Camera

What is happening?
In a closed system, atoms rearrange into products but none cross the boundary, so total measured mass remains constant.

Teacher tools

Interactive lecture

Step 1 of 100%

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1. Matter and mass

What to watch

Watch the balance and the boundary around the reaction capsule.

Chapters

Learning objectives

  • Explain conservation using atoms and system boundaries.
  • Compare mass measurements in open and closed systems.
  • Account for gas that leaves a container.
  • Apply conservation to reactions, phase changes, and dissolving.

Key concepts

During ordinary physical and chemical changes, atoms are rearranged but not created or destroyed. The total mass of a closed system remains constant.

An open-system balance reading can change because matter crosses the chosen boundary—not because matter vanished.

Try these experiments

  • Run the same reaction sealed and open.
  • Increase bicarbonate mass and compare gas production.
  • Melt and refreeze the same water sample.
  • Dissolve salt without spilling and compare mass.

Questions for exploration

  • Where is the “missing” mass in an open reaction?
  • Why must the system boundary be stated?
  • Would combustion conserve mass inside an open room?

Real-world applications

Chemical manufacturing, combustion analysis, recycling, environmental mass balances, cooking, and spacecraft life support all require matter accounting.

Common misconceptions

  • Gas has mass.
  • Atoms can rearrange without disappearing.
  • Melting does not destroy matter.
  • Apparent mass loss may mean matter crossed the boundary.

Conservation check

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