Chemistry C8

• In chemistry, a pure substance is something that only contains one compound or element throughout and is not mixed with anything else

• The boiling or melting point tells you how pure a substance is
• Impurities - lower the melting point and increase the melting range
• Impurities - increase the boiling point and may result in the sample boiling at a range of temperatures

• Useful mixtures with a precise purpose - made by following a 'formula' (recipe)
• Paints are formulations of: pigment, solvent, binder (resin) and additives
• Important in the pharmaceutical industry and everyday life (cleaning products, fuels, cosmetics, fertilisers, metal alloys, food and drink

• Mobile phase = where molecules can move, always a liquid or a gas
• Stationary phase = where molecules can't move, can be a solid or a really thick liquid

• The substances in the sample constantly move between the mobile and stationary phases - creating an equilibrium

Rf = distance traveled by substance / distance traveled by solvent

• Chlorine bleaches damp litmus paper, turning it white
• (It may turn red for a moment first though, that is because a solution of chlorine is acidic)

• If you put a glowing splint inside a test tube containing oxygen, the oxygen will relight the glowing splint

• Bubbling carbon dioxide (or shaking a carbon dioxide with) an aqueous solution of calcium hydroxide (known as limewater) causes the solution to turn cloudy

• If you hold a lit splint at the open end of a test tube containing hydrogen, you'll get a 'squeaky pop'
• The noise comes from the hydrogen burning quickly with the oxygen in the air to form H2O