Properties of MetalsProperties of Metals

T H E M E F O U R : P E R I O D I C I T Y

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Properties of MetalsProperties of Metals

T H E M E F O U R : P E R I O D I C I T Y

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Properties of MetalsProperties of Metals

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What do these pictures show you?

6.1 Properties of metals (a)describe the general physical properties of metals as solids having high melting and boiling points, being malleable,

ductile and good conductors of heat and electricity (b) describe alloys as a mixture of a metal with another element,

e.g. brass; stainless steel (c) identify representations of metals and alloys from diagrams

of structures

6.2 Reactivity series

(a) place in order of reactivity calcium, copper, (hydrogen), iron, lead, magnesium, potassium, silver, sodium and zinc, by reference to the reactions, if any, of the metals with water, steam and dilute hydrochloric acid

(b) deduce the order of reactivity from a given set of experimental results

Properties of MetalsProperties of Metals

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The Importance of Metals

• Metals are useful because of their properties.• Metals have both physical and chemical

properties.

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Physical Properties of Metals• Metals have high melting and boiling point.

A large amount of heat energy is required to overcome the strong forces of attraction between positively charged ions and delocalised electrons.

There are exceptions to the above properties of metals. E.g. Mercury and Group I metals have low melting and boiling point

• Metals are malleable ( bent to form shapes) and ductile (stretched to form wires)

Since there is a regular arrangement of ions in layers, the layers of ions can slide over each other easily when a force is applied without breaking the metallic bonds.

Physical Properties of Metals

The layers of atoms can slide over one another

Physical Properties of Metals• Good conductors of heat and electricity

Presence of mobile electrons allows electrical

charges to be transferred throughout the metal.

When one end of a piece of metal is heated, the positive ions vibrate more vigourously. The vibrating ions transfer energy to the mobile electrons. These mobile electrons move to other parts of the metal and transmit energy to other positive ions.

Physical Properties of Metals• High Density

Atoms are usually packed together as closely as

possible. Most metals have a high density because there

is little empty space between the closely packed atoms.

The 3-D arrangement of atoms in a typical metal Simplified diagram of a

metal structure. The atoms are packed together very closely.

Physical Properties of MetalsAlloys

•An alloy is a mixture of a metal with one or few of other elements (metals or non - metals)

•Alloys are much stronger and harder than pure metals.

So, why are alloys stronger and harder than pure metals?

• Different metals have different size atoms.• The different sizes of atoms disrupts the

orderly layers of atoms and makes it more difficult for the layers to slide over each other.

Physical Properties of Metals

• Thus, alloys are harder and stronger than pure metals.

Simplified structure of an alloy

Alloys

• Some examples of alloys:–Steel: Iron, carbon–Stainless steel: Iron, carbon, nickel and chromium

–Brass: Copper, Zinc

The pins of these cable plugs are made of brass

All these coins consist of copper alloy

Brass

Simple structure of brass

Copper

Zinc

•Metals have the following properties:– High densities.– High melting points.– Are malleable and ductile.– Conduct electricity & heat.

Question Time!

• List 4 physical properties of metals• What is an alloy?

• Which structure belongs to pure metal?• Which structure belongs to alloy?

AB

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•Try Eg 1 - 2

The Reactivity Series•The reactivity series is the order in which metals are listed according to their chemical reactivity.

•The most reactive metal is at the top.

Mercury

Silver

Gold

P

S

C

Potassium

Sodium

CalciumM A Z I

L H

C M

S G

MEMORISE!!!!

Reactivity SeriesPotassium PleaseSodium SendCalcium CatsMagnesium

MonkeysAluminium AndZinc ZebrasIron InLead Large(Hydrogen) HiredCopper Cage,Mercury MakeSilver SureGold Good!

PleaseStopCallingMarkAZukerbergIn LondonHe’sCalledMrSocialGuy

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Each pictures shows properties of metals.What are they ?

The Reactivity Series

• Metal ‘high up’ in the reactivity series: react vigourouslyReadily lose electrons to form + ionsCorrodes easily

• Metal ‘low down’ in the reactivity series:Does not react vigourouslyDoes not readily lose electrons to form +

ionsDoes not corrodes easily

The Reactivity Series

• The position of aluminium:Appears to be unreactive although “high” in the reactivity series

- Metal is covered with a thin layer of aluminium oxide that protects the metal from reacting.

• Hydrogen in the Reactivity Series:- Metals below hydrogen in the series do not react with acids to produce hydrogen gas.

• Examples: Copper, Mercury, Silver, Gold

• The reactivity series compares the reactivity of metals. Metals ‘high up’ in the series are very reactive. Metals ‘low down’ in the series are not very reactive.

• Metals below hydrogen do not react with acids.

Chemical Properties of Metals• Chemical properties describe how

substances react, i.e. how they change into other substances.

• Metals that react vigorously are said to be reactive metals.

• Metals that do not react are unreactive metals.

How do you know if a reaction is vigorous or

not?

Chemical Properties of Metals :Reaction of Metals with Water

• Some metals react vigorously with cold water or steam; others do not react at all.

• When a metal does react with water, the products formed are: metal hydroxide & hydrogen

Potassium is a very reactive metal, it reacts violently with water to form : Potassium hydroxide (an alkali) and Hydrogen gas

Eqn. : K (s) + H2O (l) → KOH (aq) + H2

(g)

2 2 2

Reaction of Metals with Water

Word eqn: Calcium + Water → Calcium hydroxide + Hydrogen gas

Balanced chemical equation :

Ca (s) + 2 H2O (l) → Ca(OH)2 (aq) + H2 (g)

Calcium reacts readily with cold water to form:

……………………………………………………………………………..

Calcium hydroxide & hydrogen gas

Reaction of Metals with Water• When a metal does react with steam, the products

formed are: metal oxide and hydrogen gas.

Magnesium + steam →

Magnesium oxide + Hydrogen gas

Balanced chemical equation :

Mg (s) + H2O (g) → MgO (s) + H2 (g)

Try writing the eqn! Hint: Mg is in Grp II

Chemical Properties of MetalsReaction with Dilute Hydrochloric

Acid• Many metals react with dilute hydrochloric acid.

• The products are a metal chloride and hydrogen gas.

Test for hydrogen gas:

Place a burning / lighted splint at the mouth of the

test tube. Result – The lighted

splint is extinguished with a ‘pop’ sound.

Reactions of Metals with Acid

• Check out the video:– YouTube video on potassium’s reaction with

HCl: http://www.youtube.com/watch?v=31YLkZJCea4&feature=related

Reaction with Dilute Hydrochloric Acid

copper zinc magnesium

Equations :

• Cu (s) + HCl (aq) → No reaction

Try writing the eqn!

• Zn (s) + 2 HCl (aq) → ZnCl2 (aq) + H2 (g)

Hint

Zn ion formula: Zn2+

Chlorine, Cl, is in group VII.

• Mg (s) + 2 HCl (aq) → MgCl2 (aq) + H2 (g)

Chemical Properties of Metals

MetalMetal Reaction with Reaction with Cold Water Cold Water

Reaction with Reaction with SteamSteam ObservationsObservations

Potassium

Explosion Extremely explosive

A lot of heat is produced which causes the hydrogen to catch fire and explode.Equation: 2K + 2H2O 2KOH + H2

Sodium

Vigourous Explosive

A lot of heat is produced which causes the hydrogen to catch fire and explode.Equation: 2Na + 2H2O 2NaOH + H2

Calcium

Moderate ExplsoiveEquation: Ca + 2H2O Ca(OH)2 + H2

MetalMetalReaction with Reaction with

Cold WaterCold Water

Reaction with Reaction with SteamSteam ObservationsObservations

Magnesium

Very slowVigourous

Equation: Mg (s) + 2H2O (l) → Mg(OH)2 (aq) + H2 (g)

hot magnesium burns in steam with bright lightEquation: Mg+ H2O MgO + H2

ZincNo reaction

ModerateHot zinc burns in steamequation: Zn + H2O ZnO + H2

Iron No reaction Slow

red hot iron reacts slowly with steamequation: 3Fe + 4H2O Fe3O4 (s) + 4H2

Lead No reaction No reaction

Copper No reaction No reaction

Silver No reaction No reaction

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C h a p t e r 12Chemical Properties of Metals

MetalMetal

Reaction Reaction with Dilute with Dilute HydrochloriHydrochlori

c Acidc AcidObservationsObservations

Potassium

ExplosiveEquation: 2K (s) + 2HCl (aq) → 2KCl (aq) + H2 (g)

Sodium

Explosive

Equation:

2Na (s) + 2HCl (aq) → 2NaCl (aq) + H2 (g)

Calcium

Very fast

Equation: Ca (s) + 2HCl (aq) → CaCl2 (aq) + H2 (g)

MetalMetal Reaction with Dilute Reaction with Dilute Hydrochloric AcidHydrochloric Acid ObservationsObservations

MagnesiumFast

Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2 (g)

Zinc

Moderately fast

Zn (s) + 2HCl (aq) → ZnCl2 (aq) + H2 (g)

Iron

Slowly pale green solution of iron (II) chloride is produced.

Fe (s) + 2HCl (aq) → FeCl2 (aq) + H2 (g)

LeadV. slowly

CopperNo rxn

SilverNo rxn

• Most metals react with water. The reactive metals can react with cold water.metal + water metal hydroxide +

hydrogenThe less reactive metals react when heated in steam.

metal + steam metal oxide + hydrogen

• Most metals react with dilute hydrochloric acid.

metal + hydrochloric acid metal chloride +

hydrogen

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Try Eg 3 - 5

Exercise :

1 Y is a metal. From this information alone, it may be deduced that Y

A is very reactive

B is denser than water

C cannot exist as a gas

D reacts by giving away electron(s).

2 Which one of the following best represents the structure of an alloy?

A B

C D

( C )

( D )

3 Aluminium is found to be very resistant to corrosion. Which one of the following statements correctly explain this observation?

A Aluminium is an unreactive metal

B Aluminium does not react with acid or oxygen

C The oxide layer that is formed on the surface of aluminium protect it.

D Aluminium is stronger and harder than most metals. ( C )

5 The relative positions of metals X, Y and Z in the activity series are indicated by the following abbreviated table.

Metal X

Calcium

Magnesium

Metal Y

Iron

Hydrogen

Copper

Metal Z

In each case, select from the metals X, Y and Z the one which

(i) Does not react with dilute HCl:

(ii) Reacts readily with cold water :

(iii) Does not react with cold water but reacts with dilute hydrochloric acid :

(iv) Will displace magnesium from magnesium sulfate solution :

(v) Will have no reaction with copper (II) sulfate solution :

Z

X

Y

X

Z

6 The properties of 5 metals are listed as follows :

Metal Reaction with water Reaction with dilute acids

A Does not react with steam Does not react with acids

B Sink in cold water and reacts Reacts violently with

to produce hydrogen gas dilute acids

C Reacts slowly with steam Slow effervescence with

dilute acids

D Reacts with steam to form Steady effervescence with

a yellow residue which dilute acids

becomes white when cooled

E Dissolves violently in water Too violent to react with

and floats on the surface dilute acids

as a silvery ball

a) Choose the letter that represents

(i) the least reactive metal :

(ii) the most reactive metal :

b) Choose a letter for the metal that could be

(i) Sodium : (ii) Calcium :

(iii) Copper : (iv) Iron :

(v) Zinc :

A

E

A

D

E

C

B

7) Metals and non-metals have different physical and chemical properties.

State any two differences between metals and non-metals, illustrating your answer using the properties of carbon and iron.

Iron Carbon• High melting and boiling point

• Low melting and boiling point

• High density • Low density

• Good conductor of heat

• Poor conductor of heat

• Ductile •Not ductile

•Malleable • Brittle and break easily

8) Give three physical properties of metals and suggest

three uses related to these properties.• Good conductor of electricity• Uses: Used to make electrical wires

• Ductile and malleable• Uses: Used to make electrical wires

• High melting point • Uses: Used to make the filament of light bulbs