MTLE Chemistry (Grades 9-12) cheat sheet

Stoichiometry: balance the equation first, convert grams to moles via molar mass, apply mole ratio from coefficients, convert back to requested unit; limiting reactant gives the maximum product.

Gas laws: PV = nRT with R = 0.08206 L·atm/(mol·K); combined gas law P1V1/T1 = P2V2/T2 requires Kelvin and an unchanged amount of gas.

Thermochemistry: q = mcΔT for calorimetry; ΔH of reaction from Hess's law sums step enthalpies; bond breaking absorbs energy, bond forming releases it.

Equilibrium: K expression uses products over reactants raised to coefficients, excluding pure solids and liquids; Le Châtelier shifts oppose the imposed change in concentration, pressure, or temperature.

Acid-base: pH = -log[H3O+]; at 25 °C Kw = 1.0 × 10^-14 so pH + pOH = 14; a buffer resists pH change when it contains a weak acid/base conjugate pair.

Electrochemistry: oxidation loses electrons at the anode, reduction gains electrons at the cathode; a positive standard cell potential indicates a spontaneous galvanic reaction.

Periodic trends: atomic radius decreases across a period and increases down a group; ionization energy and electronegativity generally increase across a period and decrease down a group.

Safety and lab pedagogy: model safe disposal and PPE expectations, use microscale or virtual substitutions for hazardous reagents, and require students to write a pre-lab plan identifying hazards and waste streams.

Bonding: ionic bonds form between metals and nonmetals via electron transfer; covalent bonds share electrons; polarity depends on electronegativity difference and molecular geometry.

Reaction types: synthesis, decomposition, single replacement, double replacement (precipitation or gas formation), and combustion; solubility rules predict precipitate formation in double replacement.

Kinetics: rate depends on concentration, temperature, surface area, and catalysts; a catalyst lowers activation energy without changing ΔH or equilibrium position.

Nuclear chemistry: alpha decay reduces mass number by 4 and atomic number by 2; beta decay keeps mass number constant and increases atomic number by 1; half-life problems use remaining amount = initial × (1/2)^(t/t½).

Assessment design: align items to a specific performance expectation, use multiple item types (constructed response, data analysis, lab practical), and provide scoring rubrics that separate content accuracy from reasoning quality.

Misconception targets: students often believe atoms are destroyed in reactions, that dissolving is a chemical change, and that equilibrium means equal concentrations; probe these with predict-observe-explain tasks.

Representation fluency: require translation among macroscopic observations, particulate drawings, symbolic equations, and graphs, since MTLE items test whether candidates can connect these levels.

Molarity = moles solute / liters solution; dilution uses M1V1 = M2V2; molality uses kg solvent and is temperature-independent for colligative property calculations.

Colligative properties depend on particle count: electrolyte solutions show van't Hoff factors greater than 1, so 0.1 M NaCl has roughly twice the boiling-point elevation of 0.1 M glucose.

Redox balancing in acidic solution: balance atoms, balance oxygen with water, balance hydrogen with H+, balance charge with electrons, then equalize electron transfer.

Quantum model: electron configuration follows Aufbau, Pauli exclusion, and Hund's rule; valence electrons determine group chemistry and periodic table placement.

Inquiry instruction: a 5E sequence (engage, explore, explain, elaborate, evaluate) places student investigation before formal vocabulary, supporting conceptual change.

Data literacy: distinguish accuracy from precision, identify significant figures in measurements, and require students to propagate uncertainty when reporting calculated results.

Professional practice: connect lessons to state science standards and NGSS-style three-dimensional learning (disciplinary core ideas, science practices, crosscutting concepts) when planning units.