Each chapter explains one idea that several chemistry practicals use, with its equations. Tap a chapter to open it.
Neutralisation and the endpoint
An acid and a base react in the ratio given by their equation. The point at which exactly enough of one has been added to the other is the equivalence point, and an indicator shows when you have reached it.
Redox and electrolysis
Oxidation is loss of electrons and reduction is gain, and they always happen together: every electron one substance loses, another gains. Balancing the electrons fixes the mole ratio.
The mole
Atoms are too small to count, so chemists weigh and measure volumes instead. The mole turns grams, volumes and concentrations into numbers of particles.
Identifying ions and gases
An unknown is identified by reactions only it gives: a precipitate of a certain colour, a gas with a certain test, a change no other common substance produces.
Flame colours and heating salts
Heating can identify a substance in two ways: a metal ion gives the flame its own colour, and a salt breaks down into products that show what it was.
Functional groups and their tests
An organic molecule reacts according to its functional group, so a reagent that reacts with only that group is a test for it.
Separating mixtures
The parts of a mixture are not chemically joined, so they can be separated without a reaction, by a property in which they differ: particle size, solubility, boiling point, or how far a solvent carries them.
Rates of reaction
A reaction happens when particles collide with enough energy. Anything that makes those collisions more frequent, or more of them energetic enough, speeds it up.
Reversible reactions and equilibrium
A reversible reaction goes both ways. In a closed system it settles where the two directions go at the same rate, and if the conditions change, it shifts to oppose the change.
Energy changes in reactions
Reactions give out or take in heat. The temperature change of the solution measures it, and dividing by the moles that reacted gives the enthalpy change per mole.