Master the principles governing the subject of Chemistry and you naturally master the subject. Chemistry is a subject where everything follows physical laws so much so that exceptions to the rule have their own set of rules altogether. All these 'rules' are themselves subjugated to the physical laws that keeps the universe in play. Indeed, our A Levels H2 Chemistry is not so much about solutions and chemicals per se but compounds, elements and their properties in general. Here are some materials kindly contributed by the authors of ERPZ and also other contributors.
The sets of notes supplied here cater to 2 different types of learners. The handwritten one by me largely works for those who know their stuff and only require drawings and little pointers here and there to remind you the important parts of each topic - it has more page because it covers more topics. Zhuoyi's notes consolidated from Fiveless are more comprehensive and detailed; suitable for revision use rather than just a last-minute prompt.
Gaseous Chemistry Summary - Summary of concepts under Gas Laws By Wei Seng
Chemical Periodicity Summary - Summary of Chemical Periodicity and relevant properties By Wei Seng
H2 Chemistry SPA Skill A Guide - Summary of observations and organic reactions used in Science Practical Assessment (SPA) Skill A By Wei Seng