Chapter 12: Properties of Metals

Metals

Physical Properties of Metals

1. Ductile 2. Malleable3. Good conductors of electricity 4. Good conductors of heat5. Shiny6. High melting points & boiling points7. High density8. 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.

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.

Exceptions!

Group I metals: Low melting point Low density (it floats on water)

Mercury: Liquid at room temperature Low melting point

Differentiating Metal & Non-Metal

All metals conduct electricity.

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

Alloys

In an alloy, the atoms have different sizes.

Arrangement of atoms in alloy

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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.

Metals are often used in the form of alloys because..

2. They are more resistant to corrosion.E.g. Brass [copper, zinc] is more resistant to corrosion than pure copper.

3. 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.

3. It improves the appearance. E.g. Pewter [Tin, antimony, copper] looks more beautiful than pure tin.

Some alloys..

Decorative ornaments

Bright, shiny, looks like silver

Tin, antimony, copper

Pewter

For joining metals

Low melting pointTin, leadSolder

Cutlery, utensilsResistant to corrosion, strong

Iron, chromium, nickel, carbon

Stainless Steel

Coins, musical instruments

Does not corrode easily; looks like gold

Copper, zincBrass

UsesPropertiesCompositionAlloy

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

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 No reaction under any condition

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.

(Hydrogen)

CopperSilver

Potassium

Sodium

Calcium

Magnesium

Zinc

Iron

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)

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)

24

Potassium

Sodium

Calcium

Magnesium

Aluminium

Zinc

Iron

Tin

Lead

(Hydrogen)

Copper

Silver

Gold

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Reactivity increases

Most reactive

Least reactive

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 low 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

Down a Group

Atom becomes bigger Increase in number of electron shells

Nucleus

Weaker attractive force between nucleus and valence electron

+

Valence electron (-)

Valence electron escapes easily

Valence electron (-)

+

Strong attractive force between nucleus and valence electron

Nucleus

Across a Period

Metals Non-metals Increase in tendency to lose electrons rather

than gain electrons

Sodium Chlorine

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