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8 f compounds & mixtures (boardworks)
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8 f compounds & mixtures (boardworks)

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  • 1. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 20051 of 36 KS3 Chemistry 8F Compounds and Mixtures
  • 2. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 20052 of 36 8F Compounds and Mixtures Mixtures Summary activities Comparing elements and compounds Compound names and formulae Contents Word equations
  • 3. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 20053 of 36 Properties of elements and compounds Why is it safe to put sodium chloride on fish and chips… …but not safe to use sodium and chlorine?
  • 4. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 20054 of 36 Compounds contain two or more different types of atom. Elements are materials made up of one type of atom only. Atoms in elements and compounds The element, hydrogen, exists as molecules. Each hydrogen molecule is made up of two hydrogen atoms joined together. The compound, water, exists as molecules. Each water molecule consists of two hydrogen atoms joined to one oxygen atom. H H
  • 5. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 20055 of 36 Element or compound?
  • 6. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 20056 of 36 A compound is made when atoms of different elements react and join together. For example, water is produced from the chemical reaction between hydrogen and oxygen. Making a compound – water Two hydrogen molecules react with one oxygen molecule to produce two molecules of water. + H H H H O O hydrogen oxygen water+ Why does water have different properties to its elements?
  • 7. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 20057 of 36 Properties of a compound–carbon dioxide A compound has different properties to the elements from which it is made because the atoms are joined differently. Black solid used as fuel. Colourless gas in which many substances burn. Colourless gas used in fizzy drinks and fire extinguishers. + + O OC carbon oxygen carbon dioxide+
  • 8. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 20058 of 36 A compound is not a mixture The atoms in water, the compound made when hydrogen and oxygen react and their atoms become chemically joined to each other, look like this… The atoms in a mixture of hydrogen gas and oxygen gas, which have not reacted with each other, look like this…
  • 9. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 20059 of 36 8F Compounds and Mixtures Mixtures Summary activities Comparing elements and compounds Contents Word equations Compound names and formulae
  • 10. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200510 of 36 To name simple compounds of metals and non-metals: Naming simple compounds 2. Write down the name of the non-metal, changing the ending of the word to “-ide”. 1. Write down the name of the metal. What is the name of the compound made when the following elements combine?  magnesium and oxygen  sodium and chlorine  oxygen and iron magnesium oxide sodium chloride iron oxide
  • 11. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200511 of 36 What is the name of each compound formed by these metal and non-metal elements? nitrogenlithium sulphurzinc iodinenickel brominealuminium oxygentin chlorinesodium nitrogenmagnesium sulphuriron Name of compoundElement 2Element 1 iron sulphide magnesium nitride sodium chloride tin oxide aluminium bromide nickel iodide zinc sulphide lithium nitride Naming simple compounds
  • 12. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200512 of 36 Many compounds contain more than two elements. oxygenbrominealuminium oxygensulphurcopper oxygen oxygen oxygen Element 3 nitrogensodium magnesium nitratenitrogenmagnesium nickel sulphatesulphurnickel Name of compoundElement 2Element 1 sodium nitrate copper sulphate aluminium bromate Naming further compounds For compounds containing two elements plus oxygen, the ending of the other non-metal usually changes to “--ate”.
  • 13. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200513 of 36 A compound always contains a particular amount of each element. It has a fixed composition. Composition of compounds A compound contains atoms from different elements that are chemically joined together. Compound names can get quite long and complicated, so the symbols of the elements are used as a shorthand. The symbols of the elements in a compound are combined to give the formula of the compound. What is the formula of carbon dioxide?
  • 14. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200514 of 36 carbon dioxide A formula uses the symbols of the elements in a compound. When there is more than one atom of each element, the number is always written after the symbol. Writing a formula carbon atom = 1 formula = hydrogen atoms = 2 formula = The formula shows the ratio of atoms in a compound. water CO2 H2O oxygen atoms = 2 oxygen atom = 1
  • 15. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200515 of 36 1. Titanium oxide For every titanium atom there are two oxygen atoms. Formula = 2. Lithium oxide For every two lithium atoms there is one oxygen atom. Formula = 3. Aluminium chloride For every aluminium atom there are three chlorine atoms. Formula = What is the formula of each of these compounds? What is the formula? TiO2 Li2O AlCl3 (In a formula put the metal first as when naming a compound.)
  • 16. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200516 of 36 1. Silicon chloride For every silicon atom there are four chlorine atoms. Formula = 2. Manganese oxide For every manganese atom there are two oxygen atoms. Formula = 3. Aluminium oxide For every two aluminium atoms there are three oxygen atoms. Formula = What is the formula of each of these compounds? What is the formula? SiCl4 MnO2 Al2O3 (In a formula put the metal first as when naming a compound.)
  • 17. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200517 of 36 What is the ratio of atoms?
  • 18. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200518 of 36 What does a formula show?
  • 19. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200519 of 36 8F Compounds and Mixtures Mixtures Summary activities Comparing elements and compounds Contents Word equations Compound names and formulae
  • 20. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200520 of 36 Writing a word equation A word equation can be used to describe any chemical reaction, i.e. any process in which atoms become joined in different ways. The steps for writing a word equation are: 1. On the right-handside, put the name of the reactant(s). If there are two or more reactants, link them with a ++ sign. 2. In the middle, write down an arrow ( ). 3. On the right-handside, put the name of the product(s). If there are two or more products, link them with a ++ sign.
  • 21. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200521 of 36 The lead and oxygen don’t mix, they react to form lead oxide. This means that the lead and oxygen atoms in the product are joined differently to the atoms in the reactants . Lead reacts with oxygen to form lead oxide. lead + oxygen lead oxide Why is lead oxide so different to both lead and oxygen? What is the word equation? What is the word equation for this reaction?
  • 22. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200522 of 36 1. Limestone (calcium carbonate) is heated to make calcium oxide and carbon dioxide. 2. Magnesium reacts with hydrochloric acid to make magnesium chloride and hydrogen. 3. Methane is burnt to make carbon dioxide and water. calcium carbonate calcium oxide +carbon dioxide magnesium + hydrochloric acid magnesium chloride + hydrogen methane + oxygen carbon dioxide + water What is the word equation? Write out word equations for the following chemical reactions.
  • 23. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200523 of 36 8F Compounds and Mixtures Mixtures Summary activities Comparing elements and compounds Contents Word equations Compound names and formulae
  • 24. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200524 of 36 A mixture is not the same as a compound: 1. The proportions of the substances in a mixture are not fixed. 2. The properties of a mixture are often an “average” of the properties of its ingredients (e.g. a mixture of a black and white powder is grey). 3. The substances in a mixture are just mixed, not chemically joined, and so it is usually quite easy to separate the A mixture contains two or more substances that are mixedmixed together but have not reacted with each other. Sea water is a mixture of salts, water and other substances. What is a mixture? ingredients (e.g. it is easy to get salt from sea water).
  • 25. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200525 of 36 Element, compound or mixture?
  • 26. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200526 of 36 Element, compound or mixture?
  • 27. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200527 of 36 Liquids that do not mix are described as immiscible. Examples of immiscible liquids are water with oil and water with petrol. On a small scale, immiscible liquids can be separated by simply removing the top layer using a pipette. oil water water oil Separating immiscible liquids
  • 28. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200528 of 36 Liquids that do mix are described as miscible. Examples of miscible liquids are water with alcohol and petrol with kerosine. Miscible liquids can be separated by heating them to boiling. The components of the mixture have different boiling points and so will boil off at different temperatures. A condenser is used to recover the liquids as they boil off. This piece of apparatus is a tube that has cold water circulating around the outside. It cools down vapours and condenses them back to a liquid. Substances with low boiling points are collected first, while those with higher boiling points are collected later. Separating miscible liquids
  • 29. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200529 of 36 Distillation apparatus
  • 30. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200530 of 36 How can each mixture be separated? alcoholalcohol and water cooking oilcooking oil and water watersea water saltsea water glassglass and water MethodWantedMixture filter evaporate distil pipette distil Separating mixtures
  • 31. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200531 of 36 Reggie has been given a mixture of salt, sand and water. He needs to separate these three substances but cannot remember how, so Reggie needs your help! Experiment to separate a mixture Write an experimental plan for Reggie to follow so that he will end up with the sand, salt and water in separate containers. Start your plan with a list of the equipment that is needed for separating this mixture. Then write a step by step plan that is easy for Reggie or anyone else to follow.
  • 32. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200532 of 36 8F Compounds and Mixtures Mixtures Summary activities Comparing elements and compounds Contents Word equations Compound names and formulae
  • 33. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200533 of 36 Glossary atom – The smallest particle that can exist on its own. boiling point – Temperature at which a pure liquid becomes a gas. compound – Substance made up of two or more different types of atoms that are chemically joined together. element – Substance made up of only one type of atom. formula – The symbols and numbers that represent the ratio of different atoms in a substance. immiscible – Liquids which do not mix. miscible – Liquids which do mix. mixture – Two or more substances that are mixed but not chemically joined together.
  • 34. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200534 of 36 Anagrams
  • 35. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200535 of 36 True or false?
  • 36. © Boardworks Ltd 20041 of 20 © Boardworks Ltd 200536 of 36 Multiple-choice quiz