1. 11/10/2015 AQA Chemistry 2 A slideshow that covers the entire AQA 2006 Syllabus Chemistry 2 Module W Richards

2. 11/10/2015 The structure of the atom ELECTRON – negative, mass nearly nothing PROTON – positive, same mass as neutron ( “ 1 ” ) NEUTRON – neutral, same mass as proton ( “ 1 ” ) The Ancient Greeks used to believe that everything was made up of very small particles. I did some experiments in 1808 that proved this and called these particles ATOMS: Dalton

3. 11/10/2015 Mass and atomic number ParticleRelative MassRelative Charge Proton1+1 Neutron10 ElectronVery small MASS NUMBER = number of protons + number of neutrons SYMBOL PROTON NUMBER = number of protons (obviously)

4. 11/10/2015 Mass and atomic number How many protons, neutrons and electrons?

5. 11/10/2015Isotopes An isotope is an atom with a different number of neutrons: Each isotope has 8 protons – if it didn ’ t then it just wouldn ’ t be oxygen any more. Notice that the mass number is different. How many neutrons does each isotope have?

6. 11/10/2015 Electron structure Consider an atom of Potassium: Potassium has 19 electrons. These electrons occupy specific energy levels “ shells ” … Nucleus The inner shell has __ electrons The next shell has __ electrons The next shell has the remaining __ electron Electron structure = 2,8,8,1

7. 11/10/2015 Periodic Table Introduction

8. 11/10/2015 Mendeleev Periodic table The periodic table arranges all the elements in groups according to their properties. Horizontal rows are called PERIODS Vertical columns are called GROUPS

9. 11/10/2015 HHe LiBeBCNOFNe NaMgAlSiPSClAr KCaFeNiCuZnBrKr AgIXe PtAuHg The Periodic Table Fact 1: Elements in the same group have the same number of electrons in the outer shell (this corresponds to their group number) E.g. all group 1 metals have __ electron in their outer shell These elements have __ electrons in their outer shell These elements have __ electrons in their outer shells

10. 11/10/2015 HHe LiBeBCNOFNe NaMgAlSiPSClAr KCaFeNiCuZnBrKr AgIXe PtAuHg The Periodic Table Fact 2: As you move down through the periods an extra electron shell is added: E.g. Lithium has 3 electron in the configuration 2,1 Potassium has 19 electrons in the configuration __,__,__,__ Sodium has 11 electrons in the configuration 2,8,1

11. 11/10/2015 HHe LiBeBCNOFNe NaMgAlSiPSClAr KCaFeNiCuZnBrKr AgIXe PtAuHg The Periodic Table Fact 3: Most of the elements are metals: These elements are metals This line divides metals from non- metals These elements are non-metals

12. 11/10/2015 HHe LiBeBCNOFNe NaMgAlSiPSClAr KCaFeNiCuZnBrKr AgIXe PtAuHg The Periodic Table Fact 4: (Most important) All of the elements in the same group have similar PROPERTIES. This is how I thought of the periodic table in the first place. This is called PERIODICITY. E.g. consider the group 1 metals. They all: 1)Are soft 2)Can be easily cut with a knife 3)React with water

13. 11/10/2015Compounds Compounds are formed when two or more elements are chemically combined. Some examples: Glucose Methane Sodium chloride (salt)

14. 11/10/2015 Some simple compounds… Methane, CH 4 Water, H 2 O Carbon dioxide, CO 2 Ethyne, C 2 H 2 Sulphuric acid, H 2 SO 4 Key Hydrogen Oxygen Carbon Sulphur

15. 11/10/2015 Balancing equations Consider the following reaction: Na O HH HH O H Sodium + water sodium hydroxide + hydrogen + + This equation doesn ’ t balance – there are 2 hydrogen atoms on the left hand side (the “ reactants ” and 3 on the right hand side (the “ products ” )

16. 11/10/2015 Balancing equations We need to balance the equation: Na O HH HH O H Sodium + water sodium hydroxide + hydrogen + + Na O HH O H Now the equation is balanced, and we can write it as: 2Na (s) + 2H 2 O (l) 2NaOH (aq) + H 2(g)

17. 11/10/2015 Some examples Mg + O 2 Zn + HCl Fe + Cl 2 NaOH + HCl CH 4 + O 2 Ca + H 2 O NaOH + H 2 SO 4 CH 3 OH + O 2 MgO ZnCl 2 + H 2 FeCl 3 NaCl + H 2 O CO 2 + H 2 O Ca(OH) 2 + H 2 Na 2 SO 4 + H 2 O CO 2 + H 2 O 2 2 2 3 2 2 2 2 2 2 2 2 4

18. 11/10/2015Bonding Hi. My name ’ s Johnny Chlorine. I ’ m in Group 7, so I have 7 electrons in my outer shell I ’ d quite like to have a full outer shell. To do this I need to GAIN an electron. Who can help me? Cl

19. 11/10/2015Bonding Here comes one of my friends, Harry Hydrogen Hey Johnny. I ’ ve only got one electron but it ’ s really close to my nucleus so I don ’ t want to lose it. Fancy sharing? Cl H H Now we ’ re both really stable. We ’ ve formed a covalent bond.

20. 11/10/2015Bonding Here comes another friend, Sophie Sodium Hey Johnny. I ’ m in Group 1 so I have one electron in my outer shell. Unlike Harry, this electron is far away from the nucleus so I ’ m quite happy to get rid of it. Do you want it? Cl Now we ’ ve both got full outer shells and we ’ ve both gained a charge. We ’ ve formed an IONIC bond. Na Okay Cl Na + -

21. 11/10/2015 Covalent bonding Consider an atom of hydrogen: Notice that hydrogen has just __ electron in its outer shell. A full (inner) shell would have __ electrons, so two hydrogen atoms get together and “ _____ ” their electrons: Now they both have a ____ outer shell and are more _____. The formula for this molecule is H 2. When two or more atoms bond by sharing electrons we call it ____________ BONDING. This type of bonding normally occurs between _______ atoms. It causes the atoms in a molecule to be held together very strongly but there are ____ forces between individual molecules. This is why covalently-bonded molecules have low melting and boiling points (i.e. they are usually ____ or ______). Words – gas, covalent, non-metal, 1, 2, liquid, share, full, weak, stable

22. 11/10/2015 Dot and Cross Diagrams H O H Water, H 2 O:

23. 11/10/2015 Dot and Cross Diagrams Oxygen, O 2 : O O

24. 11/10/2015 Dot and cross diagrams Water, H 2 O: Oxygen, O 2 : OH HO O H H O O O Step 1: Draw the atoms with their outer shell: Step 2: Put the atoms together and check they all have a full outer shell:

25. 11/10/2015 Dot and cross diagrams Nitrogen, N 2 : Carbon dioxide, CO 2 : Ammonia NH 3 : Methane CH 4 : H H N H H H H H C N N O O C

26. 11/10/2015 Other ways of drawing covalent bonds Consider ammonia (NH 3 ): H H N H H H N H H H N H

27. 11/10/2015Ions An ion is formed when an atom gains or loses electrons and becomes charged: If we “ take away ” the electron we ’ re left with just a positive charge: This is called an ion (in this case, a positive hydrogen ion) + - + The electron is negatively charged The proton is positively charged +

28. 11/10/2015 Ionic bonding Na + This is where a metal bonds with a non-metal (usually). Instead of sharing the electrons one of the atoms “ _____ ” one or more electrons to the other. For example, consider sodium and chlorine: Sodium has 1 electron on its outer shell and chlorine has 7, so if sodium gives its electron to chlorine they both have a ___ outer shell and are ______. A _______ charged sodium ion A _________ charged chloride ion As opposed to covalent bonds, ionic bonds form strong forces of attraction between different ions due to their opposite ______, causing GIANT IONIC STRUCTURES to form (e.g sodium chloride) with ______ melting and boiling points: Cl -

29. 11/10/2015 Some examples Mg Magnesium chloride: MgCl 2 Cl + Mg 2+ Cl - - Calcium oxide: CaO O Ca + 2+ O 2-

30. 11/10/2015 Giant structures ( “ lattices ” ) + + + + +++ + + 1. Diamond – a giant covalent structure with a very ____ melting point due to ______ bonds between carbon atoms 2. Graphite – carbon atoms arranged in a layered structure, with free _______ in between each layer enabling carbon to conduct _________ 3. Sodium chloride – a giant ionic lattice with _____ melting and boiling points due to ______ forces of attraction. Can conduct electricity when _______. 4. Metals – the __________ in metals are free to move around ( “ delocalised ” ), holding the _____ together and enabling it to conduct _________

31. 11/10/2015 A closer look at metals + + + + +++ + + Metals are defined as elements that readily lose electrons to form positive ions. There are a number of ways of drawing them: + - + - + - + - + - + - + - + - +++ +++ ++ Delocalised electrons

32. 11/10/2015Nanoscience Nanoscience is a new branch of science that refers to structures built from a few hundred atoms and are 1- 100nm big. They show different properties to the same materials in bulk. They also have a large surface area to volume ratio and their properties could lead to new developments in computers, building materials etc. Definition: Task: research nanoscience and find two current and/or future applications of this science.

33. 11/10/2015 Group 1 – The alkali metals Li Na K Rb Cs Fr

34. 11/10/2015 Group 1 – The alkali metals 1) These metals all have ___ electron in their outer shell. Some facts… 2) Reactivity increases as you go _______ the group. This is because the electrons are further away from the _______ every time a _____ is added, so they are given up more easily. 3) They all react with water to form an alkali (hence their name) and __________, e.g: Words – down, one, shell, hydrogen, nucleus, decreases Potassium + water potassium hydroxide + hydrogen 2K (s) + 2H 2 O (l) 2KOH (aq) + H 2(g) 2) Density increases as you go down the group, while melting point ________

35. 11/10/2015 Group 0 – The Noble gases He Ne Ar Kr Xe Rn

36. 11/10/2015 Group 0 – The Noble gases Some facts… 1) All of the noble gases have a full outer shell, so they are very ______ 2) They all have _____ melting and boiling points 3) They exist as single atoms rather then _________ molecules 4)Helium is ________ then air and is used in balloons and airships (as well as for talking in a silly voice) 5)Argon is used in light bulbs (because it is so unreactive) and argon, krypton and ____ are used in fancy lights Words – neon, stable, low, diatomic, lighter

37. 11/10/2015 Group 7 – The halogens F Cl Br I At

38. 11/10/2015 Group 7 – The Halogens Some facts… 1) Reactivity DECREASES as you go down the group Decreasing reactivity (This is because the electrons are further away from the nucleus and so any extra electrons aren ’ t attracted as much). 2) They exist as diatomic molecules (so that they both have a full outer shell): Cl 3) Because of this fluorine and chlorine are liquid at room temperature and bromine is a gas

39. 11/10/2015 The halogens – some reactions 1) Halogen + metal: Na + Cl - Na Cl + 2) Halogen + non-metal: H Cl + H Halogen + metal ionic salt Halogen + non-metal covalent molecule

40. 11/10/2015 Atomic mass SYMBOL PROTON NUMBER = number of protons (obviously) RELATIVE ATOMIC MASS, A r ( “ Mass number ” ) = number of protons + number of neutrons

41. 11/10/2015 Relative formula mass, M r The relative formula mass of a compound is the relative atomic masses of all the elements in the compound added together. E.g. water H 2 O: Therefore M r for water = 16 + (2x1) = 18 Work out M r for the following compounds: 1)HCl 2)NaOH 3)MgCl 2 4)H 2 SO 4 5)K 2 CO 3 H=1, Cl=35 so M r = 36 Na=23, O=16, H=1 so M r = 40 Mg=24, Cl=35 so M r = 24+(2x35) = 94 H=1, S=32, O=16 so M r = (2x1)+32+(4x16) = 98 K=39, C=12, O=16 so M r = (2x39)+12+(3x16) = 138 Relative atomic mass of O = 16Relative atomic mass of H = 1

42. 11/10/2015 A “Mole” Definition: A mole of a substance is the relative formula mass of that substance in grams For example, 12g of carbon would be 1 mole of carbon......and 44g of carbon dioxide (CO 2 ) would be 1 mole etc...

43. 11/10/2015 Calculating percentage mass If you can work out M r then this bit is easy… Calculate the percentage mass of magnesium in magnesium oxide, MgO: A r for magnesium = 24Ar for oxygen = 16 M r for magnesium oxide = 24 + 16 = 40 Therefore percentage mass = 24/40 x 100% = 60% Percentage mass (%) = Mass of element A r Relative formula mass M r x100% Calculate the percentage mass of the following: 1)Hydrogen in hydrochloric acid, HCl 2)Potassium in potassium chloride, KCl 3)Calcium in calcium chloride, CaCl 2 4)Oxygen in water, H 2 O

44. 11/10/2015 Recap questions Work out the relative formula mass of: 1)Carbon dioxide CO 2 2)Calcium oxide CaO 3)Methane CH 4 Work out the percentage mass of: 1)Carbon in carbon dioxide CO 2 2)Calcium in calcium oxide CaO 3)Hydrogen in methane CH 4

45. 11/10/2015 Calculating the mass of a product E.g. what mass of magnesium oxide is produced when 60g of magnesium is burned in air? Step 1: READ the equation: 2Mg + O 2 2MgO IGNORE the oxygen in step 2 – the question doesn ’ t ask for it Step 3: LEARN and APPLY the following 3 points: 1)48g of Mg makes 80g of MgO 2)1g of Mg makes 80/48 = 1.66g of MgO 3)60g of Mg makes 1.66 x 60 = 100g of MgO Step 2: WORK OUT the relative formula masses (M r ): 2Mg = 2 x 24 = 48 2MgO = 2 x (24+16) = 80

46. 11/10/2015 Work out M r : 2H 2 O = 2 x ((2x1)+16) = 36 2H 2 = 2x2 = 4 1.36g of water produces 4g of hydrogen 2.So 1g of water produces 4/36 = 0.11g of hydrogen 3.6g of water will produce (4/36) x 6 = 0.66g of hydrogen M r : 2Ca = 2x40 = 80 2CaO = 2 x (40+16) = 112 80g produces 112g so 10g produces (112/80) x 10 = 14g of CaO M r : 2Al 2 O 3 = 2x((2x27)+(3x16)) = 204 4Al = 4x27 = 108 204g produces 108g so 100g produces (108/204) x 100 = 52.9g of Al 2 O 3 1)When water is electrolysed it breaks down into hydrogen and oxygen: 2H 2 O 2H 2 + O 2 What mass of hydrogen is produced by the electrolysis of 6g of water? 3) What mass of aluminium is produced from 100g of aluminium oxide? 2Al 2 O 3 4Al + 3O 2 2) What mass of calcium oxide is produced when 10g of calcium burns? 2Ca + O 2 2CaO

47. 11/10/2015 Another method Try using this equation: Mass of product IN GRAMMES Mass of reactant IN GRAMMES M r of product M r of reactant Q. When water is electrolysed it breaks down into hydrogen and oxygen: 2H 2 O 2H 2 + O 2 What mass of hydrogen is produced by the electrolysis of 6g of water? Mass of product IN GRAMMES 6g 4 36 So mass of product = (4/36) x 6g = 0.66g of hydrogen

48. 11/10/2015 Problems with this technique Calculating the amount of a product may not always give you a reliable answer... 1)The reaction may not have completely _______ 2)The reaction may have been _______ 3)Some of the product may have been ____ 4)Some of the reactants may have produced other _______ The amount of product that is made is called the “____”. This number can be compared to the maximum theoretical amount as a percentage, called the “percentage yield”. Words – lost, yield, finished, reversible, products

49. 11/10/2015 Atom Economy Percentage atom economy = Relative formula mass of useful product Total masses of products Calculate the atom economies of the following: 1)Converting ethanol into ethene (ethene is the useful bit): C 2 H 5 OH C 2 H 4 + H 2 0 2)Making zinc chloride from zinc and hydrochloric acid: Zn + 2HCl ZnCl 2 + H 2

50. 11/10/2015 Numbers of moles Consider two liquids: Now consider two gases: 20cm 3 of 0.1mol/dm 3 of hydrochloric acid 20cm 3 of 0.1mol/dm 3 of sodium hydroxide These two beakers contain the same number of moles 20cm3 of helium at room temperature and pressure 20cm3 of argon at room temperature and pressure These two gases contain the same number of moles

51. 11/10/2015 Endothermic and exothermic reactions Step 1: Energy must be SUPPLIED to break bonds: Step 2: Energy is RELEASED when new bonds are made: A reaction is EXOTHERMIC if more energy is RELEASED then SUPPLIED. If more energy is SUPPLIED then is RELEASED then the reaction is ENDOTHERMIC Energy

52. 11/10/2015 Example reactions ReactionTemp. after mixing/ O CExothermic or endothermic? Sodium hydroxide + dilute hydrochloric acid Sodium hydrogencarbonate + citric acid Copper sulphate + magnesium powder Sulphuric acid + magnesium ribbon

53. 11/10/2015 Reversible Reactions Some chemical reactions are reversible. In other words, they can go in either direction: A+BC+D NH 4 ClNH 3 + HCl e.g. Ammonium chlorideAmmonia + hydrogen chloride If a reaction is EXOTHERMIC in one direction what must it be in the opposite direction? For example, consider copper sulphate: Hydrated copper sulphate (blue) Anhydrous copper sulphate (white) + Heat+ Water CuSO 4 + H 2 OCuSO 4.5H 2 O

54. 11/10/2015 Reversible Reactions When a reversible reaction occurs in a CLOSED SYSTEM (i.e. no reactants are added or taken away) an EQUILIBRIUM is achieved – in other words, the reaction goes at the same rate in both directions: A+BC+D Endothermic reactions Increased temperature: Decreased temperature: A+BC+D A+BC+D More products Less products Exothermic reactions Increased temperature: Decreased temperature: A+BC+D Less products More products A+BC+D

55. 11/10/2015 Making Ammonia Nitrogen + hydrogen Ammonia N 2 + 3H 2 2NH 3 High pressure 450 O C Iron catalyst Recycled H 2 and N 2 Nitrogen Hydrogen Mixture of NH 3, H 2 and N 2. This is cooled causing NH 3 to liquefy. Fritz Haber, 1868-1934 Guten Tag. My name is Fritz Haber and I won the Nobel Prize for chemistry. I am going to tell you how to use a reversible reaction to produce ammonia, a very important chemical. This is called the Haber Process. To produce ammonia from nitrogen and hydrogen you have to use three conditions:

56. 11/10/2015 Haber Process: The economics A while ago we looked at reversible reactions: A+BC+D Endothermic, increased temperature A+BC+D Exothermic, increase temperature ExothermicEndothermic 1) If temperature was DECREASED the amount of ammonia formed would __________... 2)However, if temperature was INCREASED the rate of reaction in both directions would ________ causing the ammonia to form faster 3)If pressure was INCREASED the amount of ammonia formed would INCREASE because there are less molecules on the right hand side of the equation Nitrogen + hydrogen Ammonia N 2 + 3H 2 2NH 3

57. 11/10/2015 Haber Process Summary 200 atm pressure 450 O C Iron catalyst Recycled H 2 and N 2 Nitrogen Hydrogen Mixture of NH 3, H 2 and N 2. This is cooled causing NH 3 to liquefy. To compromise all of these factors, these conditions are used: A low temperature increases the yield of ammonia but is too slow A high temperature improves the rate of reaction but decreases the yield too much A high pressure increases the yield of ammonia but costs a lot of money

58. 11/10/2015 Rates of Reaction Hi. I ’ m Mike Marble. I ’ m about to have some acid poured onto me. Let ’ s see what happens… Here comes an acid particle… It missed! Here comes another one. Look at how slow it ’ s going… No effect! It didn ’ t have enough energy! Oh no! Here comes another one and it ’ s got more energy…

59. 11/10/2015 Rates of Reaction Chemical reactions occur when different atoms or molecules _____ with enough energy (the “ ________ Energy): Basically, the more collisions we get the _______ the reaction goes. The rate at which the reaction happens depends on four things: 1)The _______ of the reactants, 2)Their concentration 3)Their surface area 4)Whether or not a _______ is used Words – activation, quicker, catalyst, temperature, collide

60. 11/10/2015Catalysts Task Research and find out about two uses of catalysts in industry, including: 1)Why they are used 2)The disadvantages of each catalyst

61. 11/10/2015 Catalyst Summary Catalysts are used to ____ __ a reaction to increase the rate at which a product is made or to make a process ________. They are not normally ___ __ in a reaction and they are reaction-specific (i.e. different reactions need _________ catalysts). Words – different, speed up, used up, cheaper

62. 11/10/2015 Rate of reaction graph v1 Time taken for reaction to complete Temperature/ concentration Reaction takes a long time here Reaction is quicker here

63. 11/10/2015 Rate of reaction graph v2 Amount of product formed/ amount of reactant used up Time Slower reaction Fast rate of reaction here Slower rate of reaction here due to reactants being used up Rate of reaction = amount of product formed/reactant used up time

64. 11/10/2015Electrolysis ++++++++ -------- Positive electrode Cu 2+ Negative electrode Cl - Solution containing copper and chloride ions

65. 11/10/2015Electrolysis Electrolysis is used to separate a metal from its compound. = chloride ion = copper ion When we electrolysed copper chloride the _____ chloride ions moved to the ______ electrode and the ______ copper ions moved to the ______ electrode – OPPOSITES ATTRACT!!!

66. 11/10/2015 Electrolysis equations We need to be able to write “ half equations ” to show what happens during electrolysis (e.g. for copper chloride): 2 2 2 At the negative electrode the positive ions GAIN electrons to become neutral copper ATOMS. The half equation is: Cu 2+ + e - Cu At the positive electrode the negative ions LOSE electrons to become neutral chlorine MOLECULES. The half equation is: Cl - - e - Cl 2

67. 11/10/2015 Purifying Copper ++++++++ -------- Solution containing copper ions Impure copper Cu 2+ Pure copper At the positive electrode: Cu (s) Cu 2+ (aq) + 2e - At the negative electrode: Cu 2+ (aq) + 2e - Cu (s)

68. 11/10/2015 Electrolysis of brine Positive electrode Negative electrode Sodium chloride (brine) NaCl (aq) Sodium hydroxide (NaOH (aq) ) Sodium chloride (salt) is made of an alkali metal and a halogen. When it ’ s dissolved we call the solution “ brine ”, and we can electrolyse it to produce 3 things… Chlorine gas (Cl 2 )Hydrogen gas (H 2 )

69. 11/10/2015 Universal Indicator and the pH scale Strong acid Strong alkali Neutral Universal Indicator is a mixture of liquids that will produce a range of colours to show how strong the acid or alkali is: Stomach acidLemon juiceWaterSoapOven cleanerBaking powder An acid contains hydrogen ions, H + An alkali contains hydroxide ions, OH -

70. 11/10/2015 Neutralisation reactions When acids and alkalis react together they will NEUTRALISE each other: OH Na Sodium hydroxide Cl H Hydrochloric acid The sodium “ replaces ” the hydrogen from HCl Cl Na Sodium chloride H2OH2O Water General equation: H + (aq) + OH - (aq) H 2 O (l)

71. 11/10/2015 Making salts Whenever an acid and alkali neutralise each other we are left with a salt, like a chloride or a sulphate. Complete the following table: Hydrochloric acid Sulphuric acidNitric acid Sodium hydroxide Sodium chloride + water Potassium hydroxide Potassium sulphate + water Calcium hydroxide Calcium nitrate + water

72. 11/10/2015 Making Salts Soluble salts can be made from acids by reacting them with: 1)Metals, e.g. Zn + 2HCl ZnCl 2 + H 2 2) Insoluble bases, e.g. CuO + 2HCl CuCl 2 + H 2 0 3)Alkalis (alkali = a “soluble base”), e.g. NaOH + HCl NaCl + H 2 0 Salts can be made from these solutions by crystallizing them.

73. 11/10/2015 Ammonium salts Guten tag again. When ammonia dissolves in water it produces an alkaline solution: NH 3 + H 2 0 NH 4 OH This solution can be used to make fertilisers. Very useful!

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