Unit 9 METALS

Properties of Metals

Thermal Conductivity

Electrical Conductivity

Malleable

Ductile

High Melting/Boiling Points

Ductile meaning

Can be hammered and made into different shapes

Malleable Meaning

Can be drawn into wires

Reaction of metals with Water

Form Metal Hydroxide and Hydrogen

Metal reaction with steam

Form Metal Oxide and Hydrogen

Metal Reaction with dilute acids

Form Salt and Hydrogen

Metal Reaction with Oxygen

Form Metal Oxide

Uses of aluminum and why

Aircraft due to low density

Good electrical cable due to low density and good electrical conductivity

Food container as it is resistance to corrosion

Copper uses

Electrical Wires due to good conductor and ductile

Alloy definition

Mixture of a metal with other elements

Examples of alloys

Brass- copper and zinc

Stainless steel- iron and other elements like carbon chromium and nickel

Why can alloys be more useful than pure metals?

Harder and stronger than pure metals

Uses of alloys

Stainless steel as they are hard and resistant to rusting

Why can alloys be harder and stronger than pure metals

Different sized atoms than pure metals in alloys mean that the layers can not slide over each other

Order of the reactivity series

Potassium

Sodium

Calcium

Magnesium

Aluminum

Carbon

Zinc

Iron

Hydrogen

Copper

Silver

Gold

Potassium reaction with cold water

React violently

Sodium reaction with Cold Water

React Quickly

Calcium reaction with cold water

React less strongly

Why is aluminum unreactive?

Reacts with oxygen forming protective layer of aluminium oxide which is thin, preventing reactions making it behave unreactive

Why are some metals more reactive than others

They can lose electrons more easily

Why can metals displace others

They can easily lose electrons than less reactive ones so make better reducing agents and can displace other metals

What does rusting produce

Hydrated iron (III) oxide

Conditions required for rusting

Water and oxygen

Common barrier methods of rusting

Grease, Paint, Plastic Coating

How do barriers prevent rusting

Exclude Oxygen or Water

Sacrificial Protection

More reactive metal like zinc attached to less reactive one and the more reactive one will oxidise and corrode protecting the less reactive one

Galvanising

Iron is protected by coating with a layer of zinc and forms ZnCO3

Which metals are more easy to extract

Ones that are less reactive

Describe the extraction of iron from Haemite

Burning of carbon(coke) to provide heat and produce carbon dioxide C + O2 → CO2

Reduction of Carbon Dioxide to carbon monoxide C + CO2 → 2CO

Reduction of Iron(III) oxide by carbon monoxide Fe2O3 + 3CO → 2Fe + 3CO2

Thermal Decomposition of calcium carbonate or limestone to produce calcium oxide CaCO3 → CaO + CO2

Formation of Slag removing impurities CaO + SiO2 → CaSiO3

Main Ore of Aluminium

Bauxite

Extraction of Aluminum from Bauxite

Bauxite purified to produce aluminium oxide (Al2O3)

Aluminium Oxide dissolved in molten cryolite since Aluminium Oxide has a very high melting point so doing this makes the mixture to have a lower higher point

Mixture placed in electrolysis cell made from steel lined with graphite

Graphite lining acts as negetive electrode and graphite blocks act like positive electrode

Aluminum ions gain electrons (reduction) forming molten aluminum at the bottom of the cell and molten aluminium is siphoned off from the time to time and fresh aluminium added

Al 3+ + 3e- → Al

At the anode Oxide ions lose electrons (oxidation) forming oxygen at the anode

2O2- → O2 + 4 e-

Overall 2Al2O3 → 4Al + 3O2

Carbon in the graphite anodes react with oxygen

C + O2 → CO2

Anode wears away and has to be replaced