Use the Equation Balancer to show that chemical reactions rearrange atoms, then classify reaction patterns using balanced equations.
Lesson Focus
Anchor question: when methane burns, why do the products weigh the same total amount as the reactants even though the substances look completely different? Today you will use balanced equations as evidence for conservation of mass.
Section 1Balance to Track Atoms~25 min
Reference
Reactants are the starting substances. Products are the substances made.
A coefficient changes the number of whole molecules or formula units.
A subscript is part of a chemical formula and should not be changed while balancing.
A balanced equation has the same number of each type of atom on both sides.
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Open the Equation Balancer
Adjust coefficients until the atom counts match on both sides. Use the atom table to explain how each reaction obeys conservation of mass.
Record the unbalanced equation and the balanced equation.
3
Use the atom-count table to prove the equation is balanced.
4
Repeat for synthesis, decomposition, single displacement, or double displacement examples if available.
Reaction
Balanced Equation
Atom-Count Evidence
What Changed?
Combustion
Synthesis or decomposition
Single displacement
Double displacement
Section 2Classify Reaction Patterns~25 min
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Pattern hunt
Reaction types are patterns in how atoms are rearranged. The same atoms are present before and after, but they are connected in new ways.
Synthesis
What does a synthesis reaction usually look like in terms of reactants and products?
Decomposition
How is decomposition the opposite pattern of synthesis?
Combustion
What products usually form when a hydrocarbon combusts completely?
Displacement
How can you recognize that atoms or ions have traded partners?
Coefficients vs. Subscripts
Why is it okay to change coefficients while balancing, but not okay to change subscripts inside formulas?
Use the words molecule, formula, coefficient, and subscript.
Section 3Use the Model~20 min
Claim
Agree or Disagree?
Evidence / Correction
A balanced equation proves that atoms are conserved.
If a product has a different formula, new atoms must have been created.
Changing H2O to H2O2 is a good way to balance oxygen.
!
Final Task
Karen says, "Balancing is just a math trick. It does not tell us anything real about reactions." Correct her using conservation of mass and atom counts.
Karen Prompt
Write a short correction. Include coefficients, atom counts, and rearrangement.
Exit Ticket
Answer the anchor question: why can reactants and products look different but still have the same total mass?
Finished?
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