Check whether an equation conserves atoms
Count each type of atom on both sides of a chemical equation.
Open lesson 1Conserving atoms and predicting reaction amounts
Use balanced symbolic models, mass boundaries, and stoichiometric ratios.
Before you begin
- Count formula atoms; multiply ratios; interpret grams and moles as different units.
Choose by skill rather than age alone. Read with an adult when useful, revisit a lesson, or explore another grade.
Follow the lesson sequence
Check Mass with a System Boundary
Explain apparent mass changes by tracking material across a boundary.
Open lesson 2Use Coefficients as Mole Ratios
Scale a balanced equation without changing its formulas.
Open lesson 3Find the Limiting Reactant in a Particle Model
Count complete reaction sets and leftover particles.
Open lesson 4Review and transfer
After the lessons, try 4 new review cases and a practical task. Each answer has an explanation and a link back to the related lesson.
Open the unit reviewGuest answers are temporary. Keep your own paper or document; this unit does not certify completion or record a school grade.