Subjects
Choose questions individually, practise online, or create a worksheet with matching answers. Counts include generated variants, not only authored originals.
The water molecules remain water.
Melting changes the physical state of water, not its molecular identity.
A gas.
Gas particles spread throughout the available space.
Its particles are generally much farther apart.
Compression mainly decreases the separations between gas particles.
Heating usually increases particle motion and can increase average separation; molecules are not simply inflated balls.
A response should distinguish particle size from separation.
Freezing.
Freezing changes state while retaining water as the substance.
The key explains what its shapes and colors represent.
Credit the model meaning, not claims that all atoms have those literal colors.
Use particle models without treating the spaces between particles as air.
Grades 4–7Use particle models without treating the spaces between particles as air.
Grades 4–7Separate chemical composition from physical arrangement.
Grades 5–8Separate chemical composition from physical arrangement.
Grades 5–8Track protons, neutrons and electrons separately.
Grades 7–10Track protons, neutrons and electrons separately.
Grades 7–10Use coefficients to conserve atom counts.
Grades 7–10Use coefficients to conserve atom counts.
Grades 7–10Keep molar mass, mass and amount as different quantities.
Grades 9–12Keep molar mass, mass and amount as different quantities.
Grades 9–12Find neutral ratios without assuming every metal has only one charge.
Grades 8–11Find neutral ratios without assuming every metal has only one charge.
Grades 8–11Use atomic structure to explain trends rather than treating all patterns as absolute.
Grades 8–11Use atomic structure to explain trends rather than treating all patterns as absolute.
Grades 8–11Separate bond polarity from the polarity of a whole molecule.
Grades 9–12Separate bond polarity from the polarity of a whole molecule.
Grades 9–12Balance electron accounting without confusing oxidation state with literal charge in every bond.
Grades 9–12Balance electron accounting without confusing oxidation state with literal charge in every bond.
Grades 9–12Read ligands and charge in a simple coordination formula.
Grades 11–12Read ligands and charge in a simple coordination formula.
Grades 11–12Read connectivity rather than only counting letters in a molecular formula.
Grades 8–11Read connectivity rather than only counting letters in a molecular formula.
Grades 8–11Use carbon count and the limited scope of the alkane formula.
Grades 9–12Use carbon count and the limited scope of the alkane formula.
Grades 9–12Choose a parent chain and explain what a position number means.
Grades 10–12Choose a parent chain and explain what a position number means.
Grades 10–12Recognize bond types and the restrictions of simple formula patterns.
Grades 10–12Recognize bond types and the restrictions of simple formula patterns.
Grades 10–12Locate the actual group rather than classifying by one atom alone.
Grades 10–12Locate the actual group rather than classifying by one atom alone.
Grades 10–12Compare connectivity and hydrogen-bond donor ability.
Grades 10–12Compare connectivity and hydrogen-bond donor ability.
Grades 10–12Read the groups attached to the carbonyl carbon.
Grades 10–12Read the groups attached to the carbonyl carbon.
Grades 10–12Identify structural differences without laboratory synthesis instructions.
Grades 10–12Identify structural differences without laboratory synthesis instructions.
Grades 10–12Locate nitrogen relative to a carbonyl before making comparisons.
Grades 10–12Locate nitrogen relative to a carbonyl before making comparisons.
Grades 10–12Tell changed connectivity from changed spatial arrangement.
Grades 10–12Tell changed connectivity from changed spatial arrangement.
Grades 10–12Recognize when spatial labels require enough structural information.
Grades 11–12Recognize when spatial labels require enough structural information.
Grades 11–12Connect long-chain structure with properties without universal recyclability claims.
Grades 9–12Connect long-chain structure with properties without universal recyclability claims.
Grades 9–12Use simplified provided evidence instead of treating one peak as a full identification.
Grades 11–12Use simplified provided evidence instead of treating one peak as a full identification.
Grades 11–12Track energy transferred to the surroundings separately from reaction enthalpy.
Grades 9–12Track energy transferred to the surroundings separately from reaction enthalpy.
Grades 9–12Separate a rate change from a change in equilibrium or reaction enthalpy.
Grades 9–12Separate a rate change from a change in equilibrium or reaction enthalpy.
Grades 9–12Do not confuse equal rates with equal amounts.
Grades 10–12Do not confuse equal rates with equal amounts.
Grades 10–12State the model, temperature and difference between strength and concentration.
Grades 9–12State the model, temperature and difference between strength and concentration.
Grades 9–12Use a buffer approximation only where its assumptions fit.
Grades 11–12Use a buffer approximation only where its assumptions fit.
Grades 11–12Use kelvin and specify what stays constant.
Grades 10–12Use kelvin and specify what stays constant.
Grades 10–12Keep oxidation and reduction identities separate from cell-specific signs.
Grades 10–12Keep oxidation and reduction identities separate from cell-specific signs.
Grades 10–12Count solute amount before and after adding solvent.
Grades 9–12Count solute amount before and after adding solvent.
Grades 9–12Use the balanced mole ratio and distinguish endpoint from equivalence.
Grades 10–12Use the balanced mole ratio and distinguish endpoint from equivalence.
Grades 10–12Interpret a supplied chromatogram without claiming one spot proves identity.
Grades 9–12Interpret a supplied chromatogram without claiming one spot proves identity.
Grades 9–12Use the supplied relationship within its validated range.
Grades 10–12Use the supplied relationship within its validated range.
Grades 10–12Do not confuse an impure recovered mass with a chemical yield.
Grades 10–12Do not confuse an impure recovered mass with a chemical yield.
Grades 10–12Connect monomers and linkages without saying all biological molecules are polymers.
Grades 9–12Connect monomers and linkages without saying all biological molecules are polymers.
Grades 9–12Describe catalysis without assigning intentions to molecules.
Grades 9–12Describe catalysis without assigning intentions to molecules.
Grades 9–12Relate molecular regions to behavior in water.
Grades 10–12Relate molecular regions to behavior in water.
Grades 10–12Distinguish appearance, concentration and evidence of safety.
Grades 8–12Distinguish appearance, concentration and evidence of safety.
Grades 8–12Track carbon atoms across reservoirs without treating transfers as disappearance.
Grades 9–12Track carbon atoms across reservoirs without treating transfers as disappearance.
Grades 9–12Divide mass by molar mass. Grams cancel with g/mol to leave moles; do not confuse mass with amount of substance.
Grades 9–12Multiply amount in moles by molar mass in g/mol to find mass in grams.
Grades 9–12For concentration in mol/L, convert the final solution volume from mL to L before multiplying.
Grades 9–12Divide moles of solute by the final solution volume in litres, not by solvent volume alone.
Grades 9–12Final volume is the total solution volume; assume no reaction or solute loss.
Grades 9–12Use total solution mass in the denominator: solute plus solvent. Multiply the fraction by 100.
Grades 8–11Convert purity percent to a fraction before multiplying the total sample mass.
Grades 9–12Compare actual pure product with the theoretical maximum in the same units. Yield and purity are different quantities.
Grades 9–12Divide each reactant amount by its equation coefficient. The smaller reaction extent determines the possible product.
Grades 10–12Use the balanced equation, not an assumed one-to-one ratio. Here each formula unit supplies two hydroxide ions.
Grades 10–12Use the dilute idealized aqueous model; concentrations approximate activities.
Grades 10–12The sum pH + pOH is approximately 14 for the stated dilute aqueous model at 25 °C; it changes with temperature.
Grades 10–12For a fixed amount of ideal gas at constant temperature, pressure increases as volume decreases.
Grades 10–12Use absolute temperature in kelvins. With R = 8.314 kPa·L/(mol·K), pressure in kPa gives volume in litres.
Grades 10–12Bond breaking requires energy; bond formation releases it. Average bond energies give an approximate reaction enthalpy.
Grades 10–12For the stated A ⇌ B model, use equilibrium concentrations. Other equations require different powers and expressions.
Grades 10–12Reactant concentration falls; report its positive average disappearance rate as (initial − final)/time.
Grades 10–12Subtract the anode reduction potential from the cathode reduction potential. Do not multiply potentials by equation coefficients.
Grades 11–12Measure both distances from the same origin. Rf is dimensionless and depends on the chromatographic conditions.
Grades 9–12Subtract the intercept or blank first, then divide by the slope. Use the model only within its stated calibration range.
Grades 10–12This rule requires an acyclic saturated hydrocarbon.
Grades 9–12CnH2n applies here to an acyclic hydrocarbon with one double bond. A formula alone does not distinguish an alkene from a cycloalkane.
Grades 10–12In complete hydrocarbon combustion, each carbon atom contributes one CO₂ molecule. This is a paper stoichiometry model.
Grades 10–12For a saturated acyclic monohydric alcohol, CnH2n+2O, sum all atom masses. The formula is also compatible with ether isomers.
Grades 10–12For a neutral closed-shell hydrocarbon, each ring or double bond adds one DBE; a triple bond adds two.
Grades 11–12Multiply repeat-unit molar mass by the number of repeat units. This simplified model ignores end-group masses.
Grades 10–12A single unbranched noncyclic peptide with n amino-acid residues has n − 1 links between adjacent residues.
Grades 10–12Formula reference
Grades 9–12Formula reference
Grades 8–12Formula reference
Grades 9–12Formula reference
Grades 10–12Formula reference
Grades 10–12Formula reference
Grades 9–12Formula reference
Grades 10–12Formula reference
Grades 10–12A dynamic chemical equilibrium has balanced forward and reverse rates under the specified conditions, not necessarily equal reactant and product amounts.
UniversityA dynamic chemical equilibrium has balanced forward and reverse rates under the specified conditions, not necessarily equal reactant and product amounts.
UniversityA molecular formula constrains composition but can correspond to multiple constitutional or stereochemical structures.
UniversityA molecular formula constrains composition but can correspond to multiple constitutional or stereochemical structures.
UniversityThis formula applies to a first-order rate law and not generally to zero- or second-order reactions.
UniversityThis formula applies to a first-order rate law and not generally to zero- or second-order reactions.
UniversityThe reaction quotient is dimensionless; use the electron count for the balanced reaction as written.
UniversityThe reaction quotient is dimensionless; use the electron count for the balanced reaction as written.
UniversityConvert entropy to the same energy unit as enthalpy. Temperature is in kelvin.
UniversityConvert entropy to the same energy unit as enthalpy. Temperature is in kelvin.
University