Foundations

Optical power, directional power and surface densities are different quantities.

Photometry weights radiation with a specified standard visual response.

Symbol form, spacing and parentheses preserve the meaning of reported quantities.

Mass prefixes attach to gram even though kilogram is the SI base unit.

Report useful digits without treating extra digits as proof of accuracy.

Common non-SI unit names require their correct SI scale factors.

Molecular collisions link macroscopic pressure to random translational motion.

Solid, liquid and gas describe bulk behavior rather than chemical identity.

Element mass ratios become atom ratios through molar masses, with uncertainty and sample identity retained.

A Lewis diagram accounts for bonding and nonbonding valence electrons in a specified connectivity.

VSEPR distinguishes the arrangement of electron regions from the positions of atoms.

Polar bonds can cancel in a molecule; molecular geometry matters.

Dissolution disperses specified molecular or ionic species in a solvent.

A saturation limit is an equilibrium property under specified conditions, not a synonym for concentration.

Ordinary filtration separates undissolved particles; dissolved species can remain in the filtrate.

Distillation uses vapor–liquid partitioning and condensation, with a limit at an azeotrope.

Genomic sequence variants and observable traits describe different levels of biological information.

Substrate recognition and catalysis depend on a dynamic molecular environment.

Covalent subunit linkage and water-assisted cleavage explain biological polymer structure.

Sugar connectivity distinguishes energy-storage and structural polysaccharides.

Lipids include several architectures rather than one repeating-monomer polymer class.

The peptide backbone and variable side chains are different parts of protein structure.

Bases carry sequence information on a chemically directional sugar–phosphate backbone.

A cell's boundary, fluid interior and specialized structures have different roles.

A source location or magnitude does not describe the shaking experienced at every site.

Composition and temperature structure describe different features of Earth's atmosphere.

Surface drainage boundaries depend on the chosen outlet and need not bound groundwater flow.

A sky direction is an angular observation, not an object's three-dimensional distance.

Celestial angular coordinates require a declared reference system and date conventions.