GCSE Chemistry notes

Everything is made of atoms. Knowing the particles inside an atom and how they are arranged underpins the whole of chemistry.

Bonding explains why substances have the properties they do. The three types — ionic, covalent and metallic — each come from how electrons are shared or transferred.

Quantitative chemistry lets you predict exactly how much product a reaction gives. It rests on the mole, Mr and the conservation of mass.

Chemical changes rearrange atoms into new substances. This topic covers acids, the reactivity series, salt preparation and electrolysis.

Chemical reactions transfer energy to or from the surroundings. Bond breaking is endothermic; bond making is exothermic — the difference is the overall energy change.

Rate of reaction is how fast reactants are used up or products are formed. Collision theory explains every factor that changes it.

Organic chemistry is the chemistry of carbon compounds. At GCSE the focus is crude oil, hydrocarbons and simple reactions of alkanes and alkenes.

Analysis lets chemists identify substances and check purity. Techniques range from chromatography and Rf values to simple gas and ion tests.

Today's atmosphere is roughly 78% nitrogen and 21% oxygen. Human activity is now changing its composition, causing climate change.

Chemistry provides the materials we depend on. Sustainable use means treating water carefully, assessing product life cycles and recycling metals and polymers.