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© Boardworks Ltd 2003. A slide contains teachers notes wherever this icon is displayed - To access these notes go to Notes Page View (PowerPoint 97) or.

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Presentation on theme: "© Boardworks Ltd 2003. A slide contains teachers notes wherever this icon is displayed - To access these notes go to Notes Page View (PowerPoint 97) or."— Presentation transcript:

1 © Boardworks Ltd 2003

2 A slide contains teachers notes wherever this icon is displayed - To access these notes go to Notes Page View (PowerPoint 97) or Normal View (PowerPoint 2000). Normal ViewNotes Page View Teachers Notes Flash Files A flash file has been embedded into the PowerPoint slide wherever this icon is displayed – These files are not editable.

3 © Boardworks Ltd 2003 Elements and Compounds two or more types of atom. It follows that compounds contain two or more types of atom. The water molecule contains two hydrogen atoms bonded to one oxygen atom, so the formula is H 2 O. one type of atom only. Elements are materials made up of one type of atom only. Hydrogen molecule contains two hydrogen atoms bonded together, so the formula is H 2.

4 © Boardworks Ltd 2003 Compounds: Water Compounds are produced when elements combine. For example, water is produced in the following reaction. Word Equation Hydrogen + Oxygen Water + + Two water molecules react with one oxygen molecule to give water.

5 © Boardworks Ltd 2003 Compounds – not mixtures The atoms in compounds are NOT mixed together. A mixture of hydrogen and oxygen would look like: bondedchemical reaction. very They become bonded together during a chemical reaction. Because of this compounds have properties that are very different to the elements that they are made from. HYDROGEN Flammable gas. OXYGEN Gas in which many substances burn. WATER Liquid that extinguishes most fires. +

6 © Boardworks Ltd 2003 Compounds – not mixtures Black solid used as barbecue fuel Gas in which many substances burn Gas used in fizzy drinks and fire extinguishers carbon + oxygen carbon dioxide

7 © Boardworks Ltd 2003 Naming Simple compounds. It is easy to name simple compounds of metals and non- metals. 1.Write down the name of the metal 2.Write down the name of the non-metal but change the ending to ide. oxygencalcium sulphursilver brominecopper Name of compoundElement 2Element 1 copper bromide silver sulphide calcium oxide 1) magnesium 2) oxygen = magnesium oxide 1) sodium 2) chlorine = sodium chloride

8 © Boardworks Ltd 2003 Name the compound formed from these 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.

9 © Boardworks Ltd 2003 Naming more complicated Compounds plus –ate. Many compounds contain more than two elements. Naming them can get complicated but for those containing two elements plus oxygen the name ending usually changes to –ate. oxygenbrominealuminium oxygensulphurcopper oxygen Element 3 nitrogensodium magnesium nitratenitrogenmagnesium nickel sulphatesulphurnickel Name of compoundElement 2Element 1 sodium nitrate copper sulphate aluminium bromate

10 © Boardworks Ltd 2003 The composition of compounds. Compounds are very different to the elements from which they are made but there is another way in which compounds are different to mixtures. In a mixture you can add any amount of the ingredients. Compounds always contain a definite amount of each element. They have a fixed composition. This is not really surprising as looking at the word equations you will have seen they always have a definite number of element atoms joined together. NaCl OOC MgO O H H

11 © Boardworks Ltd 2003 The formula of compounds This means that every compound can have a formula that tells us how many of each type of atom are present. We include small slightly dropped numbers if there are more of one atom than the other.Water One oxygen atom Two hydrogen atoms H 2 O Formula H 2 O O H H Carbon dioxide One carbon atom Two oxygen atoms CO 2 Formula CO 2 OOC

12 © Boardworks Ltd 2003 What is the formulae of each of the compounds shown? (As with names, put the metal first.) 2. Lithium Oxide Li O ? oxygen atom ? lithium atoms Formula? 3. Aluminium chloride ? aluminium atom ? chlorine atoms Formula Al Cl 1. Titanium oxide ? titanium atom ? oxygen atoms Formula Ti OO 1 titanium atom 2 oxygen atoms Formula TiO 2 1 oxygen atom 2 lithium atoms Formula Li 2 O 1 aluminium atom 3 chlorine atoms AlCl 3 Formula AlCl 3 Activity The formula of compounds

13 © Boardworks Ltd 2003 What is the formulae of each of the compounds shown? Silicon chloride ? silicon atom ? chlorine atoms Formula Si Cl Manganese oxide Manganese oxide ? manganese atom ? oxygen atoms Formula Mn OO 1 manganese atom 2 oxygen atoms MnO 2 Formula MnO 2 1 silicon atom 4 chlorine atoms SiCl 4 Formula SiCl 4 Cl Aluminium oxide ? aluminium atom ? oxygen atoms Formula Al O O O 2 aluminium atom 3 oxygen atoms Al 2 O 3 Formula Al 2 O 3 Al Activity The formula of compounds

14 © Boardworks Ltd 2003 Word equations can be used to describe any chemical change. (i.e. any process where the atoms become joined (bonded) in different ways). The steps are: + 1.Write down the name of the reactant(s) linking them with a + sign if there is more than one. 2.Write down an arrow + 3.Write down the names of the products linking them with a + sign if there is more than one Word Equations

15 © Boardworks Ltd 2003 It hasnt just mixed. It has reacted and atoms are joined differently. Write out word equations for this reaction Lead reacts with oxygen to form lead oxide Lead + oxygen lead oxide LeadLead oxide Why is lead oxide so different to both lead and oxygen? Activity Word Equations

16 © Boardworks Ltd 2003 Write out word equations for the following reactions. 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 Activity Word Equations

17 © Boardworks Ltd 2003 Mixtures mixed Mixtures are, as the name indicates, mixed rather than reacted together. This means that, unlike compounds: 1 They do not have to have any particular proportions of the various ingredients. 2 Their properties are often an average of the properties of their ingredients. (eg. a mixture of a black and white powder is grey!) sea water: a mixture of salts and water 3 They are mixed, not bonded, and so are usually not too hard to separate back into their ingredients. (For example, it is easy to get salt from sea water.)

18 © Boardworks Ltd 2003

19 Immiscible liquids Immiscible means doesnt mix and so we are talking about mixtures like water with cooking oil or water with petrol. On a small scale you can simply remove the top layer using a pipette. oil water oil Separating Mixtures

20 © Boardworks Ltd 2003 Miscible liquids Miscible means does mix and so we are talking about mixtures like water and alcohol or petrol with kerosine. These are separated by boiling them as it is unlikely that they will boil at exactly the same temperature. In order to get back the liquids we use a condenser. This is a tube that has cold water circulating through the outside. It cools down vapours and condenses them back to a liquid. Substances with low boiling points collect first, while those with higher boiling points collect later. Separating Mixtures

21 © Boardworks Ltd 2003 condenser electric heater collection beaker water in water out thermometer Distillation Equipment Miscible liquids

22 © Boardworks Ltd 2003 Separations How would you get this? MixtureWantedMethod Glass and waterglass Sea watersalt Sea waterwater Cooking oil & watercooking oil Alcohol and wateralcohol filter evaporate distil pipette distil

23 © Boardworks Ltd 2003 John has been given a mixture of salt, sand and water. He needs to separate them but cannot remember how. Can you help him? Write an experimental plan for John to follow so that he can have the sand, salt and water in separate containers. Make sure you start off by telling him what equipment he will need. Then he will need a step by step plan that is easy to follow. Separation Experiment

24 © Boardworks Ltd 2003 Summary activities

25 © Boardworks Ltd Which of these is a compound? A.bromine B.copper C.carbon dioxide D.uranium

26 © Boardworks Ltd 2003 best 2.Which of these best describes a compound? A.Two or more atoms bonded together. B.Two or more elements mixed together. C.Two or elements bonded together. D.Two or more types of molecule mixed together.

27 © Boardworks Ltd 2003 best 3.Which of these could best describe compounds? Substances that: A.are similar to the elements that they are made from. B.can be formed when elements react together. C.can be formed when elements decompose into two or more new substances. D.substances with symbols in the Periodic Table.

28 © Boardworks Ltd What would be the name of a compound formed from sulphur, oxygen and zinc? A.sulphur zincide B.sulphur zincate C.zinc sulphide D.zinc sulphate

29 © Boardworks Ltd What would be the formula of a compound containing two aluminium atoms for every three sulphur atoms? A. Al 2 S 3 B. Al 3 S 2 C. Al 2 S 3 D. Al 3 S 2

30 © Boardworks Ltd How would you separate a mixture of water and alcohol. (Two miscible liquids) A.filtering B.chromatography C.evaporation D.distillation

31 © Boardworks Ltd What is the main technique you would use when separating a mixture of salt and sand? A.filtering B.chromatography C.evaporation D.distillation

32 © Boardworks Ltd Use the chromatogram to decide which dyes are in the ink. A B C D Ink


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