Chemistry sits between the descriptive and the mathematical, and students usually find one half much harder than the other. The descriptive half — bonding, the periodic table, reactions of groups — rewards precise language. The quantitative half — moles, concentration, yield — rewards careful, methodical arithmetic.
The single most common source of lost marks is imprecision. "It gets bigger" where the mark scheme wants "the rate of reaction increases"; "they share electrons" where it wants "a shared pair of electrons between two non-metal atoms". Chemistry marks are awarded for saying the right thing in the right words, so learn the definitions as they are written.
Required practicals are examined directly, and questions tend to focus on why a step is done rather than what the step is. Know the purpose of each stage, the variables and the main sources of error.
These notes cover each topic with worked examples and the mistakes examiners see most often. Use them alongside practice questions rather than instead of them.
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