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 9–12Divide 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 9–12Divide each reactant amount by its equation coefficient. The smaller reaction extent determines the possible product.
Grades 10–12Formula reference
Grades 9–12