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21/07/2015 Compounds and Mixtures Elements 21/07/2015 If a solid, liquid or gas is made up of only one type of atom we say it is an element. For example, consider a tripod made up of iron: These atoms are ALL iron – there’s nothing else in here Compounds Compounds are different to elements. They contain different atoms. Here are some examples: Glucose 21/07/2015 Methane Sodium chloride (salt) 21/07/2015 Some simple compounds… Methane, CH4 Water, H2O Carbon dioxide, CO2 Key Hydrogen Ethyne, C2H2 Oxygen Sulphuric acid, H2SO4 Carbon Sulphur Making compounds 21/07/2015 Compounds are made when two or more elements (or compounds) go through a chemical reaction. For example: 1) When carbon reacts with oxygen it usually forms ____ _________ 2) When oxygen reacts with hydrogen it could form ______ 3) When iron reacts with oxygen it could form ______ ______ There are usually “tell-tale” signs to show when a compound is being made, such as bubbling, heat given off, colour changes, fizzing etc. Water, iron oxide or carbon dioxide? Naming compounds 21/07/2015 Rule 1 – When two elements join the end is usually _______ide. e.g. Magnesium + oxygen magnesium oxide 1) Sodium + chlorine 6) KBr 2) Magnesium + fluorine 7) LiCl 3) Lithium + iodine 8) CaO 4) Chlorine + copper 9) MgO2 5) Oxygen + iron 10)KF Naming compounds 21/07/2015 Rule 2 – When three or more elements combine and one of them is oxygen the ending is _____ate e.g. Copper + sulphur + oxygen Copper sulphate 1) Calcium + carbon + oxygen 6) AgNO3 2) Potassium + carbon + oxygen 7) H2SO4 3) Calcium + sulphur + oxygen 8) K2CO3 4) Magnesium + chlorine + oxygen 5) Calcium + oxygen + nitrogen Naming compounds 21/07/2015 Rule 3 – If two identical elements combine then the name doesn’t change This happens with the following elements: 1) H2 4) F2 2) N2 5) Cl2 3) O2 6) Br2 These elements always go around in pairs. For example, hydrogen looks like this: Mixtures Before 21/07/2015 After Element, mixture or compound? 21/07/2015 Salty water Hydrogen Hydrochloric acid Air Diamond Sodium chloride (salt) Air 21/07/2015 Air is a mixture… 1% 21% 0.03% Oxygen Nitrogen 79% Carbon 79% dioxide Noble gases 18% Separating air 21/07/2015 Air can be separated into the different gases that make it up. To do this you first have to cool air down to -2000C and turn it into a liquid: Nitrogen Liquid air Fractional distillation Argon Oxygen In this chamber the air is gradually heated up again and the different parts of air “distil” off at different temperatures according to their boiling points