Key Terms

• Acid: Acids produce hydrogen ions (H+) in aqueous solutions and have a pH range of 0-6
• Alkali: Alkalis produce hydroxide ions (OH-) in aqueous solutions and have a pH range of 8-14
• Crystallisation: A separation technique used to produce solid crystals from a solution by evaporating the solvent
• Displacement: A chemical reaction where a more reactive element displaces a less reactive element from its compound
• Electrolysis: The splitting up of an ionic compound using electricity, causing chemical reactions at the electrodes and the decomposition of materials
• Electrolyte: A solution containing free ions from the molten or dissolved ionic substance, allowing ions to move and carry charge
• Extraction: Techniques used to separate a desired substance when mixed with others
• Filtration: A separation technique used to separate solids from liquids
• Negative electrode (cathode): The electrode where hydrogen is produced if the metal in the electrolyte is more reactive than hydrogen, and where positively charged ions gain electrons in reduction reactions
• Neutralisation: The reaction when an acid and a base react to form water and a salt
• Oxidation: A reaction involving the gain of oxygen and the loss of electrons
• pH scale: A measure of the acidity or alkalinity of a solution, ranging from 0 to 14, determined using universal indicator or a pH probe
• Positive electrode (anode): The electrode where oxygen is produced unless the solution contains halide ions, then the halogen is produced, and where negatively charged ions lose electrons in oxidation reactions
• Reduction with carbon: Metals less reactive than carbon can be extracted from their oxides by reduction with carbon
• Strong acid: A strong acid is completely ionised in aqueous solution, examples include hydrochloric, nitric, and sulfuric acids
• The reactivity series: Metals arranged in order of reactivity, used to predict products from reactions
• Universal indicator: A mixture of dyes that changes color gradually over a range of pH, used in testing for acids and alkalis
• Weak acid: A weak acid is only partially ionised in aqueous solution, examples include ethanoic, citric, and carbonic acids