AQA GCSE Chemistry Topic 4: Chemical Changes

Reactivity of Metals

Refers to a metal's tendency to form cations when reacting with other substances, with a higher tendency indicating higher reactivity. The reactivity series lists metals in order of reactivity.

Extraction of Metals and Reduction

Describes the process of extracting metals from compounds, often using carbon for less reactive metals. Reduction involves the gain of electrons, as per the OILRIG principle.

Oxidation and Reduction in Terms of Electrons

OILRIG principle explains oxidation as loss and reduction as gain of electrons. Charges should balance in chemical equations, with cations losing electrons and anions gaining them.

Reactions of Acids with Metals

Involves the reaction of acids with metals to form salt and hydrogen, following the principles of oxidation and reduction.

Neutralisation of Acids and Salt Production

Neutralization reactions between acids and alkalis/bases produce salts and water. The type of salt formed depends on the reactants involved.

Soluble Salts

Form when an acid reacts with a solid insoluble substance, requiring the solid to be added until it no longer dissolves, followed by crystallization.

The pH Scale and Neutralization

pH scale measures acidity/basicity, with lower pH indicating stronger acids. Neutralization involves the reaction of H+ and OH- ions to form water.

Titrations

Used to determine the concentration of an unknown substance in a solution, involving a step-by-step process to calculate concentrations accurately.

Strong and Weak Acids

Strong acids completely ionize in solution, leading to low pH, while weak acids only partially ionize. The strength refers to the concentration of H+ ions in the solution.

Electrolysis

Involves passing a current through a solution to break down compounds into elements, with ions moving to electrodes based on charge. It is used for extracting metals and producing substances like aluminum.