Classification, bonding, atomic models, isotopes and periodic trends.
What makes a substance a substance? How do chemists sort the matter ar...
Salt dissolved in water looks simple — but is it an element, compound ...
How do you get pure water from seawater, or iron filings from sand? Ph...
Chromatography, crystallisation, and fractional distillation — the mor...
Bring together everything from lessons 1–4. Solve extended problems an...
Test your knowledge of Lessons 1–5
Why do atoms bond at all? Understanding what drives bonding unlocks ev...
Table salt conducts electricity when dissolved but not when solid. The...
Two non-metals sharing electrons creates everything from water to diam...
Metals conduct, bend without breaking, and are shiny. The sea of deloc...
Why does water have a much higher boiling point than expected? The for...
Test your knowledge of Lessons 6–10
From plastic bags to DNA, polymers are everywhere. Their properties co...
"Like dissolves like" is one of the most useful rules in chemistry. Un...
From hard spheres to electron clouds — the model of the atom changed s...
Carbon-12, Carbon-13, Carbon-14 — same element, different masses. Isot...
Mendeleev arranged 63 elements and left gaps for undiscovered ones. Ho...
Test your knowledge of Lessons 11–15
Every chemical property of an element comes down to how its electrons ...
Why do atoms get smaller across a period but larger down a group? Atom...
How much energy does it take to remove an electron from an atom? Ionis...
Apply atomic theory and periodic trends to unfamiliar contexts. Practi...
Connect the threads: classification, bonding, atomic structure and per...
Full module assessment covering all 20 lessons