← Chemistry syllabus

MassachusettsChemistry

Module 3: Chemical reactions and stoichiometry

6 dot points across 6 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

Why must a chemical equation be balanced, and how does balancing express the conservation of mass?

Write and balance chemical equations, and use them to show that atoms and mass are conserved in a reaction (MA STE HS-PS1-7(MA), conservation of mass).
A standard-level answer on balancing chemical equations and the conservation of mass for Massachusetts high school chemistry: reading a formula equation, balancing by coefficients, and using the balanced equation to show atoms and mass are conserved, grounded in HS-PS1-7(MA).
12 min answer →

When two reactants are mixed, which one runs out first, and how much product do we really get?

Identify the limiting reactant, calculate the theoretical yield, and find the percent yield of a reaction (MA STE HS-PS1-7(MA), quantitative reasoning in reactions).
A standard-level answer on limiting reactants and percent yield for Massachusetts high school chemistry: finding which reactant runs out first, calculating the theoretical yield from it, and comparing actual to theoretical yield as a percentage, grounded in HS-PS1-7(MA).
13 min answer →

How do we convert between the mass of a substance and the number of particles or moles it contains?

Calculate molar mass, convert between mass, moles, and particles, and find percent composition and empirical formulas (MA STE HS-PS1-7(MA), proportional reasoning with chemical formulas).
A standard-level answer on molar mass and percent composition for Massachusetts high school chemistry: finding molar mass from a formula, converting between mass, moles, and particles with Avogadro's number, and calculating percent composition and empirical formulas, grounded in HS-PS1-7(MA).
13 min answer →

How do we track the movement of electrons during a chemical reaction?

Identify oxidation and reduction by the transfer of electrons, assign oxidation numbers, and recognize oxidizing and reducing agents (MA STE HS-PS1-2, electron behavior in reactions).
A standard-level answer on oxidation-reduction reactions for Massachusetts high school chemistry: defining oxidation and reduction by electron transfer, assigning oxidation numbers, identifying oxidizing and reducing agents, and recognizing redox in everyday processes, grounded in HS-PS1-2.
12 min answer →

How does a balanced equation let us predict the amount of product from a given amount of reactant?

Use mole ratios from a balanced equation to calculate the amounts of reactants and products in mole-to-mole and mass-to-mass problems (MA STE HS-PS1-7(MA), proportional reasoning in reactions).
A standard-level answer on stoichiometric calculations for Massachusetts high school chemistry: reading mole ratios from a balanced equation and using them for mole-to-mole and mass-to-mass calculations through the mole-ratio bridge, grounded in HS-PS1-7(MA).
13 min answer →

How can we classify chemical reactions, and how does the type help us predict the products?

Classify reactions as synthesis, decomposition, single replacement, double replacement, or combustion, and predict the products from the reactants (MA STE HS-PS1-2, predicting reaction outcomes).
A standard-level answer on classifying chemical reactions for Massachusetts high school chemistry: the five main reaction types (synthesis, decomposition, single replacement, double replacement, combustion), how to recognize each, and using the type and an activity series to predict products, grounded in HS-PS1-2.
12 min answer →