Chemistry, down to the atom.
Start with something real, like salt in water. Zoom in until you can watch the atoms do it, then push them around yourself. Written for GCSE and A-level, and checked against IUPAC and NIST.
Start with something real
Every lesson has a Core page and a Deeper page.
Why does salt dissolve in water?
Water molecules pull the crystal apart, one ion at a time.
Why do reactions go faster when it’s hot?
More collisions, and many more of them hard enough to react.
Why is a water molecule bent?
Electron pairs push each other as far apart as they can.
Why does a reaction push back when you change it?
Le Chatelier’s principle, shown with molecules you can count.
Where are the electrons in an atom?
Shells, subshells and orbitals, filled one electron at a time.
Why do metals burn with different colours?
Electrons jump up, fall back and give out light at exact wavelengths.
How do you count atoms you can’t see?
The mole: a number of particles you can weigh out.
What does pH actually measure?
Each step on the scale is ten times more hydrogen ions.
Every element signs its name in light
Heat an element and its electrons jump up, then fall back and give off light at exact wavelengths. Spread that light out and you get these lines. They are why sodium street lamps were orange, and how we know what the Sun is made of.
Read the lessonThe whole subject, mapped
Chemistry as it is taught, in eight families of ideas. 8 lessons are written so far, out of 25 planned. Each one is checked against its sources before it goes up, and the list of what is still being written is public.
Open the map