Chapter 13: Properties of Metals

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

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

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.

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. Push

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

Differentiating Metal & Non-Metal All metals conduct electricity.

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

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

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

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. PUSH

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

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.

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

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

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

Reactivity Series of Metals An arrangement of 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.

Metal Reaction with water Sodium Reacts very fast with cold water, sometimes with explosion, produces sodium hydroxide and H2(which may catch fire and explode) Potassium Explodes with cold water, potassium hydroxide and H2 produced a lot of heat given off, H2 gas burns in air Calcium Reacts readily with cold water, calcium hydroxide obtained together with lots of bubbles of H2 Zinc No reaction with cold water; hot zinc burns in steam to produce zinc oxide and H2 Iron No reaction with cold water, rusting occurs slowly in the presence of air. Red hot iron reacts slowly with steam to produce iron oxide and H2 Silver No reaction under any condition Copper Magnesium Reacts very slowly with cold water; a few bubbles of H2 gas produced; magnesium hydroxide solution obtained. Hot magnesium burns to produce magnesium oxide and hydrogen gas; H2 burns in air.

Revealing the True Order Potassium Sodium Calcium Magnesium Zinc Iron 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 (Hydrogen) Copper Silver 21

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 Magnesium + Steam  Magnesium oxide + Hydrogen Mg(s)+ H2O(g)  MgO(s) + H2(g)

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)

Most reactive Reactivity increases Least reactive 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

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

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

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.

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.

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.

Reactivity and the Periodic Table

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

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

So… What have we learnt?

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