Learning objective: demonstrate electrolysis as the decomposition of a molten salt by an electric current see patterns in the changes at the electrodes during electrolysis explain electrolysis in terms of ions describe and illustrate the extraction of aluminium explain the changes during the extraction in terms of ions NaCl 13/06/2016 Write the formulae for the following ionic compounds: Sodium chloride (Na + & Cl - ) Copper (I) oxide (O 2- ) Calcium hydroxide (Ca 2+ & OH - ) Potassium phosphate (K + & PO 4 3- ) NaCl Cu 2 O Ca(OH) 2 K 3 PO 4

Which type of element forms at the negative electrode? Which type of element forms at the positive electrode? Suggest a rule with which to predict what will happen at the electrodes during the electrolysis of molten salts. Predict the products at the electrodes during the electrolysis of these molten compounds: sodium iodide; magnesium chloride; calcium bromide What differences between liquids and solids might help to explain the observation that sodium chloride conducts when liquid but not when solid? How does sodium chloride differ from a metal as an electrical conductor?

Ions and electrodes At the cathode (-) metal ions gain electrons (reduction) Na + + e -  Na Al e -  Al Cu e -  Cu At the anode (+) non-metal ions lose electrons (oxidation) 2 Br -  Br e - 2 O 2-  O e - 2 Cl -  Cl e -

Extraction of aluminium Watch the video and animation of the extraction of aluminium from its oxide .  Label the diagram and answer the questions

Electrolysis of aluminium oxide Why is the aluminium oxide (Al 2 O 3 ) dissolved in cryolite? Why does the electrolyte remain molten? Cathode: Al e -  Al Anode: 2 O 2-  O e - What happens to the anodes?

Metallic bonding Watch the animation showing bonding in aluminium Using this and the information on pages describe metallic bonding – use words and diagrams

Properties of metals strong in tension strong in compression can be hammered or pressed into shape without breaking; they are malleable have high melting points conduct electricity Structure of metals Metals have a giant structure of atoms. The metal atoms give up electrons to form a ‘sea’ of negative electrons shared between them. The attraction between the positive charge on the metal atoms and negative charge on the electrons holds the atoms together strongly. The bonding electrons are free to move.

The life cycle of metals Annotate the sheet during the slideshow

2Iron is the most abundant metal in the lithosphere. 3All the really valuable ores come from underground mining. Metal ores – true or false? 1All metals are found in the Earth as compounds.   

A vein of gold in quartz rock

The mineral ore haematite (iron oxide) is mined as the principal source of the metallic element iron.

A disused tin mine in Cornwall

A crane filling railroad cars in an open cast copper mine

1The removal of oxygen from a metal compound is called reduction. 2Carbon is oxidized in a blast furnace. 3Aluminium oxide conducts electricity when solid and when liquid. Metal extraction – true or false? 

A blast furnace runs continuously, making hundreds of thousands of tons of iron per year.

carbon anodes solid crust of electrolyte insulation molten aluminium oxidemolten aluminium tapping hole carbon lining of cell (cathode) + - Making aluminium by electrolysis

2All metals conduct electricity when solid and when liquid. 3All metals corrode in moist air. Metal properties and uses – true or false? 1All metals are strong in tension.  

Which properties of metals does this illustrate?

2The bonding between metal atoms is strong. 3An electric current in a metal is a flow of electrons. Metal structure and bonding – true or false? 1Metals are made up of molecules. 

In a metal crystal the atoms are packed as close together as possible. This is a giant structure.

Metallic bonding is strong bonding. Each metal atom contributes one or two electrons to a shared ‘sea’ of electrons. The shared bonding electrons can move through the whole metal structure.

2Recycling rates are higher for metals than most other materials. 3Recycled steel is not as strong as new steel. Metal waste and recycling – true or false? 1Iron is the only metal that can be recycled economically.  

What are the economic and environmental benefits of recycling iron?

What are the economic and environmental benefits of recycling aluminium?

Haematite dug from ground High quality ore does not need purifying Blast furnace Casting/Steel manufacture e.g. steel girders and ‘tin’ cans Magnetic

Bauxite dug from ground Dissolving in sodium hydroxide; filter; acidify Electrolysis Casting/Alloying e.g. drinks cans 31% Al from recycled scrap – up to 95% less energy used