HS-PS1-7

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

Clarification statement: Emphasis is on using mathematical ideas to communicate the proportional relationships between masses of atoms in the reactants and the products, and the translation of these relationships to the macroscopic scale using the mole as the conversion from the atomic to the macroscopic scale. Emphasis is on assessing students’ use of mathematical thinking and not on memorization and rote application of problem-solving techniques.

Assessment boundary: Assessment does not include complex chemical reactions.

Reference Tables

Relevant reference tables:

• Periodic Table of the Elements
• Mathematical Relationships – 1 mole = molar mass (g) = 6.02 × 10²³ particles = 22.4 L at STP

Regents Exam Questions

Released New York State Regents exam questions that assess HS-PS1-7 are listed here by exam and question cluster. Each link opens the question with its answer key.

Exam	Cluster	Question
August 2026 Chemistry Regents	Electricity Generation in New York State	Question 3
	The Fruit Industry in New York State	Question 8
	The ABCs of Ultraviolet Radiation	Question 29
	Catalytic Converter in Cars	Question 31
June 2026 Chemistry Regents	Chemistry of Beverages	Question 6
	The Accidental Development of Breathable, Waterproof Fabric	Question 15
	Balloon Arches	Question 24
	Chip Bag: PFAS vs PLA Plastics	Question 33
Chemistry sample clusters (Spring 2025)	Smartphone Chemistry	Question 3
	A Profitable Blueberry Field	Question 4
	A Profitable Blueberry Field	Question 5

Vocabulary

Terms from the Chemistry Glossary that come from this standard or from the released exam questions that assess it.

From this standard

• atom
• chemical property
• chemical reaction
• claim
• closed system
• conservation of atoms
• conservation of mass
• conversion factor
• element
• energy
• gas
• macroscopic scale
• mass
• mathematical representation
• matter
• mole
• particle
• phenomenon
• product
• properties
• proportional relationship
• reactant
• reaction
• volume

From released exam questions

• balanced equation – Aug 2026
• bioplastic – June 2026
• bond – June 2026
• climate change – Aug 2026
• coefficient – June 2026
• complete combustion – Aug 2026
• concentration – June 2026
• conservation of matter – Aug 2026, June 2026
• criteria – June 2026
• evidence – Sample 2025
• high temperature – June 2026
• molar mass – June 2026
• molecule – June 2026
• monomer – June 2026
• oxide – Sample 2025
• pressure – June 2026
• significant figures – June 2026, Sample 2025
• solution – June 2026
• substance – June 2026, Sample 2025
• synthesis – Aug 2026
• temperature – June 2026

Implied by this standard

• Avogadro’s number – implied by "the mole as the conversion from the atomic to the macroscopic scale"
• molar volume (22.4 L/mol at STP) – implied by "calculate a quantity (e.g. # of particles, volume of a gas)"
• mole ratio – the Smartphone Chemistry rubric multiplies by "2 moles Al₂O₃ / 4 moles Al".
• stoichiometry – implied by "proportional relationships between masses of atoms in the reactants and the products"
• structural formula – drawn but not named in June 2026 Chip Bag Figure 1 and the June 2026 Equilibria in the Blood rubric.

Performance Level Descriptions

Every Regents exam question on HS-PS1-7 is written to match one of the performance level descriptions (PLDs) below.

Level 1: Use information provided to identify mathematical representations that demonstrate atoms and/or mass are conserved during a chemical reaction. Aug 2026 · Q8

Level 2: Use or complete a mathematical representation to demonstrate that atoms and/or mass are conserved during a chemical reaction. June 2026 · Q33 June 2026 · Q15

Level 3: Construct a mathematical representation and/or calculate a quantity (e.g. # of particles, volume of a gas, etc.), using the relationship that atoms and/or mass are conserved during a chemical reaction. Aug 2026 · Q31 Aug 2026 · Q3 Aug 2026 · Q29 June 2026 · Q24 June 2026 · Q6 Sample · Profitable Blueberry Field Q4 Sample · Smartphone Chemistry Q3

Level 4: Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction. Sample · Profitable Blueberry Field Q5

Level 5: Create and revise mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.

Notice: PLD levels!

Resources

Examples and discussion of resources for the learning, teaching, and assessment of HS-PS1-7.

This section could be expanded upon. You can help out by adding to this section.

NGSS Dimensions

Performance expectation HS-PS1-7 was developed using the following elements from the NRC document A Framework for K-12 Science Education:

Science and Engineering Practices

• Using Mathematics and Computational Thinking
  • Use mathematical representations of phenomena to support claims.

Disciplinary Core Ideas

• PS1.B: Chemical Reactions
  • The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

Crosscutting Concepts

• Energy and Matter
  • The total amount of energy and matter in closed systems is conserved.

Page contributors: Conrad Richman, Caroline Leonard

Chemistry | HS. Chemical Reactions