Metals

1. Metals Properties of Metals & Non-metals Reactions of Metals & Their Compounds Reactivity Series Unreactive Behaviour of Aluminium Rusting & Prevention Alloys Uses of Metals Extraction of Metals Recycling – Advantages & Disadvantages

2. Elements are classified into metals or non-metals. • Metals lose electrons to form positive ions. Thus, they behave as reducing agents. • Non-metals gain electrons to form negative ions. Thus, they behave as oxidising agents.

3. High melting /boiling points Conducts electricity in molten and solid state Good conductor of heat Shiny appearance Malleable & ductile Sonorous High density (generally) Low melting /boiling points Does not conduct electricity Poor conductor of heat Dull appearance Brittle Not sonorous Low density (generally) Differences Between Metals & Non-Metals NON-METALS METALS

4. Reactions of Metals with Oxygen • Sodium & Potassium react readily with oxygen to form oxides or peroxides. 4Na + O2 2Na2O 2Na + O2 Na2O2 • Calcium and other metals react with oxygen, on heating, to form oxides. 2Ca + O2 2CaO (white solid) 2Fe + O2 2FeO (black solid)

5. 4Al + 3O2 2Al2O3(white solid) 2Cu + O2 2CuO (black solid) • Gold is unreactive and does not react with oxygen on heating.

6. Reaction of Metals with Water

7. Reaction of Metals with Water

8. Reaction of Metals With Water Copper shows no reaction with cold water or steam Go to http://www.wpbschoolhouse.btinternet.co.uk/page03/Reactivity.htm#layer

9. Reaction of Metals with Water Effervescence not seen easily. Solution is clear. Effervescence seen here. Resulting solution turns cloudy.

10. Reaction of Metals with Steam • The wet sand / wet cotton wool is heated to generate steam.

11. Potassium floats on water. Sparks formed. Catches fire. Hissing sound. Heat evolved. What would you expect to see if universal indicator were added to the solution? Ans : Green Universal Indicator turns purple. The resulting solution is alkaline.

12. Calcium sinks in water. Effervescence seen. Heat evolved. White insoluble solid formed as product. The resulting solution turns chalky. What is the white solid? • Ans : Calcium hydroxide

13. Answers to Questions 1. Al, Zn, Fe, Sn, Pb 2. Sodium

14. Reaction of Metals With Dilute Hydrochloric Acid

15. Reaction of Metals With Dilute Hydrochloric Acid

16. Reaction of Metals With Dilute Hydrochloric Acid

17. Answers to Questions • Zinc (Copper shows no reaction with dilute acids) • Iron (Transition element – Copper not acceptable as it does not react with dilute acids) • The insoluble lead (II) chloride formed coats the lead, preventing any further reaction.

18. Metal Displacement Reactions • A more reactive metal displaces a less reactive metal from a solution of its salt. eg. 1 : When iron is added to copper (II) sulphate solution , iron displaces copper from its solution. This occurs as iron is more reactive than the metal present in solution i.e. copper (II) ions.

19. Reaction of Iron with Copper (II) Sulphate Solution

20. Changes : • Blue solution turns pale green due to presence of iron (II) ions. • A reddish brown solid / deposit is formed due to metallic copper formed. • The mixture turns warm as heat is given off during the exothermic reaction • Fe + CuSO4 FeSO4 + Cu

21. e.g. 2 : When magnesium is added to iron (II) sulphate solution , magnesium displaces iron from its solution. This occurs as magnesium is more reactive than the metal present in solution i.e. iron (II) ions.

22. Reaction of Magnesium with Iron (II) Sulphate Solution

23. Changes : • Pale green solution turns colourless due to formation of magnesium ions. • A grey solid / deposit is formed due to metallic iron formed. • The mixture turns warm as heat is given off during the exothermic reaction. • Mg + FeSO4 MgSO4 + Fe

24. e.g. 3 : When copper metal is added to magnesium (II) sulphate solution , no reaction occurs as copper does not displace magnesium from a solution of its ions. This is because copper is less reactive than magnesium & therefore cannot displace magnesium from a solution of its salt. Changes : No visible reaction.

25. Copper added to Aqueous Silver Nitrate

26. Displacement of metals from metal oxides • This type of reaction can also be classified as a redox reaction. • Here, a more reactive metal can displace a less reactive metal from its oxide. • Both the metal & metal oxide are heated strongly in a crucible. e.g. Mg + ZnO MgO + Zn e.g. Cu + ZnO no reaction

27. Heat the mixture in a crucible strongly. • The magnesium oxide formed is a white ash.

28. Effect of hydrogen on heated oxides • Hydrogen can reduce some oxides of metals like iron (III) oxide & oxides of metals less reactive than iron in the reactivity series. i.e. iron, lead, copper, mercury, silver. • e.g. CuO + H2 Cu + H2O (black solid) (reddish brown solid) • e.g. ZnO + H2 no reaction

29. Reaction of Hydrogen with Metal oxides Copper (II) oxide Acid + Metal Add acid to a reactive metal to generate hydrogen gas. The hydrogen is then passed over heated copper (II) oxide.

30. Effect of carbon on heated oxides • Carbon can reduce some oxides of metals like zinc oxide & oxides of metals less reactive than zinc in the reactivity series. i.e. zinc, iron, lead, copper, mercury, silver. • e.g. 2ZnO + C 2Zn + CO2 (white solid)(grey solid) • e.g. 2Fe2O3 + 3C 4Fe + 3CO2 (reddish (grey solid) brown solid) • e.g. CaO + C no reaction

31. Answers to Questions • a) B, C, A b) Zinc

32. Reactions of metal carbonates • Potassium and Sodium carbonate (& ammonium carbonate) are soluble in water. • All other metal carbonates (excluding group I metal carbonates) are insoluble in water. • Potassium carbonate and sodium carbonate are stable compounds and therefore, cannot be decomposed by heating. This is because potassium and sodium are very reactive metals & form very stable compounds. e.g. Na2CO3 no reaction heat

33. All other carbonates decompose on heating to form metal oxides and carbon dioxide gas. • e.g. CaCO3 CaO + CO2 (white solid) (white solid) • e.g. ZnCO3 ZnO + CO2 (white solid) (yellow solid when hot) (white solid when cool) • e.g. CuCO3 CuO + CO2 (green solid) (black solid)

34. Answers to Questions 1.a) W, Y, X b) Sodium / Potassium 2.a) P is Carbon dioxide Bubble the gas through limewater. If the gas is carbon dioxide, a white ppt is formed in limewater. b) White solid turns yellow when hot. On cooling, yellow solid turns white.

35. The Reactivity Series Decreasing Reactivity K Potassium (Please) Na Sodium (Send) Ca Calcium (Cheetahs) Mg Magnesium (Monkeys) Al Aluminium (And) Zn Zinc (Zebras) Fe Iron (In) Sn Tin (Ten) Pb Lead (Large) H Hydrogen (Hired) Cu Copper (Cages) Hg Mercury (Make Ag Silver (Sure) Au Gold (Gates) Pt Platinum (Padlocked) Go to http://www.wpb4.btinternet.co.uk/page12/9Fmc.htm to do quizzes.

36. Alloys • Alloys are mixtures of two or more metals. Sometimes, non-metals are present in the mixture. • Examples of alloys: • Stainless steel ( Fe, C, Cr & Ni) • Bronze ( Cu & Sn) • Brass ( Cu & Zn)

37. Alloys are stronger & harder than pure metals. • This is because : • There are atoms of different sizes with the alloy. • The different sizes of atoms disrupt the orderly arrangement of atoms. • This makes it difficult for the layers of atoms to slide over each other when a force is applied.

38. Atoms are of same sizes ; Orderly arrangement of atoms ; Force applied causes the layers of atoms to slide off easily.

39. Uses of Metals & Alloys • Tin : Used in soldering wires or pieces of metal together due to its low melting point. • Zinc : Used in galvanising of steel or iron, where zinc corrodes in place of less reactive metals like iron. • Nickel : Used in making of engines of aircraft as it has a high melting and boiling point. It maintains its strength and does not corrode easily at high temperatures.

40. Tungsten : Used in filaments of light bulbs as it has a high melting point and high resistance to current flow. • Copper : Used in electrical cables, cooking pots and pans as it is a good electrical and heat conductor and is corrosion resistant.

41. Aluminium is used in: • Fuel tanks of vehicles/ aircraft due to its low density; • Cooking pots & pans due to its low density, good heat conductivity & its resistance to corrosion. • Soft drink cans due to its low density & corrosion resistance; • Parts of motor vehicles, bodies of buses due to its low density; • Reflectors in car headlights, big lamps at stadium as it is a good reflector of light. • Duralumin is an alloy of aluminium. It is strong, light, hard & used in aircraft construction. It is made of aluminium, copper, manganese, magnesium & sometimes some silicon.

42. Alloys of Copper : • Brass : Made of copper & zinc; Used to make pins of electric plugs, ornaments & door handles as it is corrosion resistance. • Bronze : Made of copper & tin; Stronger than brass & more corrosion resistant. Used to make propellors of ships as it is hard & corrosion resistant ; cooling containers as it is a good conductor of heat & is corrosion resistant.

43. Alloys of iron : • Mild Steel : 99% iron, 1% manganese & silicon, 0.2% carbon. Used in buses, cars, ships and steel rods in the construction industry as it is strong & hard. • Stainless Steel : Made up of iron, carbon, chromium & nickel. Used for chemical industries, medical instruments & cutlery like knives, forks etc. as it does not rust.

44. Unreactive Behaviour of Aluminium : • Aluminium is a fairly reactive metal in the reactivity series. However, it appears unreactive. • This is due to the formation of a protective layer of aluminium oxidewhen pure aluminium is exposed to oxygen in air. 4Al + 3O2 2Al2O3 • The aluminium oxide formed is very unreactive and does not allow the aluminium atoms beneath to react with other substances.

45. Pure Aluminium When exposed to air / oxygen Layer of Unreactive Aluminium Oxide Aluminium If the layer of aluminium oxide is scraped off, the underlying layer of aluminium will react vigorously.

46. Rusting & Rust Prevention • Iron and steel can corrode when exposed to oxygen in air and moisture. The product of corrosion is a reddish-brown solid called rust. Hence, this process is called rusting. • All other metals that can corrode DO NOT form rust & therefore, cannot undergo rusting. • Rust is actually hydrated iron (III) oxide.

47. Conditions for rusting to occur : a) oxygen b) moisture / water • Rusting occurs faster if salts are dissolved in the water into which iron is placed i.e. salt water increases the rate of rusting.

48. Rust Prevention : Methods of rust prevention are : • Coating with paint • Coating with oil / grease • Coating with plastic • Tin plating • Chromium plating • Galvanising iron / steel (Coating iron / steel with a layer ofzinc)

49. Paint, oil / grease, plastic, tin and chromium are substances that are unreactive or less reactive than iron / steel. When these substances are coated onto iron / steel, they form a protective layer. • As long as the layer is not scratched off, the iron / steel is protected. If the layer is scratched, the iron / steel is exposed to oxygen and moisture, and will start to rust.

50. Layer of paint, oil, tin, plastic or chromium Iron / Steel Iron / Steel If layer is scratched, iron is exposed to air and moisture and will rust readily