Mississippi Science PHS.4.3

ScienceGrades 9–12Physical Science

The Standard

PHS.4: Students will analyze changes in matter and the relationship of these changes to the law of conservation of matter and energy.

Apply the concept of conservation of matter to balancing simple chemical equations.

2026 Mississippi College- and Career-Readiness Standards for Science · The Law of Conservation of Matter and Energy

Teacher's field guide

What Students Need to Do: Students count each type of atom on both sides of a chemical equation. They add whole-number coefficients until the counts match, without changing the formulas.
What Mastery Looks Like: A student balances H2 + O2 → H2O as 2H2 + O2 → 2H2O. They can show four hydrogen atoms and two oxygen atoms on each side.
Common Misconceptions: Students may change subscripts instead of adding coefficients, which changes the substances. They may also count molecules rather than atoms and think both sides need the same number of molecules.
How to Assess It: Ask students to balance Fe + O2 → Fe2O3. Have them write the iron and oxygen atom counts on each side.

Lesson moves

Use four blue H beads and two red O beads to build 2H2 and O2, then rearrange them into 2H2O.
Show H2 + O2 → H2O and ask, "Why can't we change H2O to H2O2 to balance it?"
Give pairs cards for Mg + O2 → MgO and N2 + H2 → NH3; partners race to balance them and check atom counts.
Show a photo of a rusty bike chain, then have students balance Fe + O2 → Fe2O3 and track the atoms.

Free download

A ready-to-print activity worksheet aligned to PHS.4.3, with an answer key for the teacher on its own page. No account needed.

PDF, US Letter, prints cleanly in black and white.

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