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Metals

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Metals

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  1. Chapter 12: Properties of Metals Metals

  2. Physical Properties of Metals • Ductile • Malleable • Good conductors of electricity • Good conductors of heat • Shiny • High melting points & boiling points • High density • Strength

  3. Structure of Metals • Metals are generally solids. [Recall: Particulate Models of Matter] • Simplified diagram of a metal:

  4. Structure of Metals: Explanation • Metals have high density because there is little empty space between the atoms. Atoms are packed close together in a metal.

  5. Push Structure of Metals: Explanation • In pure metals, atoms of the same size are packed regularly in layers. • Metals are malleable and ductile because the layers of atoms can slide over each other easily when a force is applied.

  6. Exceptions! • Group I metals: • Low melting point • Low density (it floats on water) • Mercury: • Liquid at room temperature • Low melting point

  7. Differentiating Metal & Non-Metal All metals conduct electricity.

  8. If you were a SPARTAN.. Would you use pure metal or an alloy to make your armour?

  9. Alloys • Mixtures of a metal with another element • For example, • Bronze: copper and tin • Brass: copper and zinc • Stainless steel: iron, chromium, nickel and carbon

  10. Arrangement of atoms in alloy Alloys • In an alloy, the atoms have different sizes.

  11. PUSH Alloys • The different sizes of the atoms • disrupts the orderly layers of atoms, and • makes it more difficult for the layers to slide over each other.

  12. PUSH Metals are often used in the form of alloys because.. • They are harder and stronger.

  13. Metals are often used in the form of alloys because.. • They are more resistant to corrosion. E.g. Brass [copper, zinc] is more resistant to corrosion than pure copper. • It lowers the melting points of metals. E.g. Solder [tin, lead] has lower m.p. than pure tin or pure lead, and can be used to join metals. • It improves the appearance. E.g. Pewter [Tin, antimony, copper] looks more beautiful than pure tin.

  14. Alloy Composition Properties Uses Brass Copper, zinc Does not corrode easily; looks like gold Coins, musical instruments Stainless Steel Iron, chromium, nickel, carbon Resistant to corrosion, strong Cutlery, utensils Solder Tin, lead Low melting point For joining metals Pewter Tin, antimony, copper Bright, shiny, looks like silver Decorative ornaments Some alloys..

  15. Question! Do you think metals react in the same manner?

  16. Metals • may react more or less violently than others • the metal that reacts more vigorously is said to be more reactive than the other metal • metals have different reactivities

  17. Reactivity Series of Metals • Anarrangementof metals in order of their ease of reaction, beginning with the most reactive • The position of a metal in the series determines • Reactions of the metal with various reagents • Displacement of one metal from its compound by another metal • Method of extraction of a metal from its ore.

  18. Revealing the True Order Potassium Sodium Hydrogen is inserted as a reference point Metals above H: Reacts with HCl and water/steam Metals below H: No reaction with HCL and water Calcium Magnesium Zinc Iron (Hydrogen) Copper Silver

  19. Write the Chemical Equation! Reaction with water/steam • Metal + (cold) Water Metal hydroxide + Hydrogen • Example: • Potassium + Water  Potassium hydroxide + Hydrogen • 2K(s) + 2H2O(l)  2KOH(aq) +H2(g) • Metal + Steam  Metal oxide + Hydrogen • Example: • Magnesium + Steam  Magnesium oxide + Hydrogen • Mg(s)+ H2O(g)  MgO(s) + H2(g)

  20. Write the Chemical Equation! Reaction with dilute hydrochloric acid • Metal + Hydrochloric acid  Metal chloride + Hydrogen • Example: • Magnesium + Hydrochloric Acid  Magnesium chloride + Hydrogen • Mg(s) + 2HCl(aq)  MgCl2(aq) + H2(g)

  21. Potassium Sodium Calcium Magnesium Aluminium Zinc Iron Tin Lead (Hydrogen) Copper Silver Gold Please Stop Calling Me A Zebra I Think Larry Hoo Can See Girls Most reactive Reactivity increases Least reactive 24

  22. Be Creative! Come up with your set of mnemonics Share it with the class! 5mins to Brainstorm

  23. The Position of Aluminium • Aluminium does not appear to react with water or steam. Shouldn’t it be low in the reactivity series?

  24. The Position of Aluminium • A thin layer of aluminium oxide protects the metal from reacting. What happens when this layer of oxide is removed? • Aluminium will react with steam a little less vigorously than magnesium, according to the reactivity series.

  25. Using the Reactivity Series • Predict chemical reactions of metals E.g. Copper does not react with water under any condition. We can predict that gold will also have no reaction with water since it is less reactive than copper.

  26. Reactivity Series: An explanation • When metals react with water/dilute acid, they lose electrons to become ions. The more readily a metal gives up electrons to form ions, the more reactive it is. • Reactivity Series: A measure of how easily a metal gives up electrons to form positive ions.

  27. Reactivity and the Periodic Table

  28. Valence electron (-) Valence electron (-) + + Nucleus Nucleus Strong attractive force between nucleus and valence electron Weaker attractive force between nucleus and valence electron Down a Group • Atom becomes bigger • Increase in number of electron shells Valence electron escapes easily

  29. Across a Period • Metals  Non-metals • Increase in tendency to lose electrons rather than gain electrons Sodium Chlorine

  30. So… What have we learnt?

  31. Summary • The higher the metal in the reactivity series, the more reactive the metal • The more reactive the metal, the more violent are the reaction with HCl and water • Reaction of metal with HCl • Metal + HCl  Metal chloride + Hydrogen • Reaction of metal with water/steam • Metal + Water Metal hydroxide + Hydrogen • Metal + Steam Metal oxide + Hydrogen