C8

• a pure substance contains just one element or contains just one compound
• to test for oxygen, put a glowing splint into the gas and if oxygen is present it will relight
• the melting and boiling points of pure substances are one specific temperature
• to test for carbon dioxide, bubble through limewater and if carbon dioxide is present it will turn milky
• the melting and boiling points of impure substances change state over a range of temperatures
• to test for chlorine, add damp litmus paper and if chlorine is present is will be bleached white
• formulation is a complex mixture designed as a useful product
• examples of formulations: 1. fuels 2. alloys 3. fertilisers
• chromatography is a process to separate the constituents of a mixture
• to test for hydrogen, put a lit splint into the gas and if hydrogen is present it will make a popping sound
• in chromatography, the solvent must be below the start line so substances don't dissolve in the solvent
• in chromatography, the line is drawn in pencil because the pencil won't dissolve in solvent
• the Rf value depends on how soluble the substance is in the solvent
• Rf value = distance moved by spot/distance moved by solvent
• in paper chromatography, the stationary phase is the paper and the mobile phase is the solvent