Science (2015) Grade(s): 09-12 - Physical Science


Use mathematical representations to support and verify the claim that atoms, and therefore mass, are conserved during a simple chemical reaction.

Unpacked Content

Scientific and Engineering Practices

Using Mathematics and Computational Thinking

Crosscutting Concepts

Energy and Matter


Students know:
  • Matter can be understood in terms of the types of atoms present and the interactions both between and within them.
  • Chemical reactions, which underlie so many observed phenomena in living and nonliving systems alike, conserve the number of atoms of each type but change their arrangement into molecules.


Students are able to:
  • Students use the mole to convert between the atomic and macroscopic scale in the analysis.
  • Given a chemical reaction, students use the mathematical representations to predict the relative number of atoms in the reactants versus the products at the atomic molecular scale.
  • Given a chemical reaction, students use the mathematical representations to calculate the mass of any component of a reaction, given any other component.


Students understand that:
  • When substances react chemically with other substances to form new substances with different proporties, the atoms are combined and rearranged to form new substances, but the total number of each atom is conserved and the mass does not change.
  • The property of conservation can be used to help describe and predict the outcomes of reactions.


  • Atoms
  • Conservation
  • Chemical reaction
  • Mass
  • Balanced chemical equation
  • Reactants
  • Products
  • Molar mass
  • Avogadro's number
  • Stoichiometry
  • Ion
  • Molecule
  • Law of conservation of mass
  • Polyatomic ion