Module 2

Rock Cycle

Metals

The Air

Uses of Metals

Iron is used for girders, transport and cutlery.

Copper is used in coinage, water pipes, electrical wiring and ornaments.

Aluminium is used for window frames, aircraft and pans.

Extracting Metals from Ores

The most reactive metals are most

difficult to extract from their ores.

The least reactive metals are the

easiest to extract from their ores.

REACTI VI TYSERI ES

METHOD OF EXTRACTI ON

SodiumCalcium

MagnesiumAluminium

Energy is required to extract them f romtheir ores, because they are veryreactive. ELECTROLYSI S is used. Metalsare f ormed at the cathode.

CarbonZincI ron

Copper

These metals are below carbon in thereactivity series and are extracted byheating with carbon/ carbon monoxide.

GoldPlatinum

These metals are unreactive and existNATURALLY. They are obtained byphysical processes, eg panning.

REDUCTION

• Reduction is the loss of oxygen from a compound.

Copper oxide + Carbon

heat Copper + Carbon dioxide

REDUCTION

Purification of copper and half-equations.

• The anode is made of impure copper and the cathode is made of pure copper.

• At the anode (+) copper ions pass into solution.

• At the cathode (-) copper atoms are deposited.

• The solution must contain copper ions and is usually copper (II) sulphate. Half Equations.

The reactions at the electrodes can be written as half-equations. This means that we write separate equations for what is happening at each of the electrodes during electrolysis.

For the purification of copper by electrolysis.

At the CATHODE (-): Cu2+ + 2e- REDUCTION CuBlue copper (II) solution gains two electrons pinky brown copper metal

At the ANODE (+): Cu OXIDATION Cu2+ + 2e-

Copper metal blue copper (II) solution loses two electronsThe solution of copper sulphate does not alter in concentration during the process,

if everything is working as it should. The copper atoms change to copper(II) ions and leave the anode to go into solution at just the same rate that copper (II) ions arrive at the cathode and change into copper atoms.

TRANSITION METALS

TRANSITION METALS

In general the transition metals…

• have high melting points

• have high densities

• are good conductors of electricity and heat

• often form coloured compounds

Some of them are in common use eg.

Wires, pans,girders, ornaments, cars,

jewellery.

Rocks and the Rock Cycle

IGNEOUS

SEDIMENTARYMETAMORPHIC

Rocks, classify the following rocks;

GRANITE

LIMESTONE

SLATE

BASALT

MARBLE

SANDSTONE

1 2

3

6

4 5

Process 1 & 5 - the rock melts to form MAGMA, which wells up from the MANTLE and COOLS DOWN either ABOVE or WITHIN the Earth’s crust.

Features;

a hard rock consisting of interlocking crystals

which are large if the rock has cooled slowly

and small if it has cooled quickly.

Process 2 & 6 - made from layers of SEDIMENT whose weight squeezes out WATER causing particles to become CEMENTED together, YOUNGER rocks therefore are usually on top.

Features;

a grainy and crumbly rock which sometimes

contains fossils by which the rock can be

dated

Process 3 & 4 - the rock is formed by extreme TEMPERATURE and PRESSURE caused by MOUNTAIN BUILDING processes which force SEDIMENTARY rocks deep underground near to MAGMA where they are COMPRESSED and HEATED changing their TEXTURE and STRUCTURE. They can be formed from any rock type.

Features;

usually hard rocks containing tiny crystals

on cooling, could contain distorted fossils. They are

chemically identical to the rocks they are

formed from.

The Earth’s Atmosphere.

N2

O2

CO2

Rest

CO2

O2RestCO2

N2

4 billion years ago

Present day

2.5 billion years ago

Volcanic activity releases

• mainly CARBON DIOXIDE, and

• smaller amounts of hydrogen, carbon monoxide and nitrogen with

• WATER VAPOUR which condenses as the Earth cools to form the oceans.

Primitive green plants evolve and

•CARBON DIOXIDE is reduced as plants take it in and release OXYGEN

• microorganisms which can’t tolerate OXYGEN die off

• carbon from CARBON DIOXIDE is locked up in sedimentary rocks as carbonates and fossil fuels. Carbonates are formed as a result of carbon dioxide dissolving in the oceans.

• More NITROGEN is added to the atmosphere as a result of DENITRIFYING BACTERIA on nitrates from decaying plant materials.

• The oxygen in the atmosphere is now much increased

• Some of it is converted to OZONE which protects animals from the full extent of the Sun’s UV radiation. New species evolve.

• There is a state of balance because

• PHOTOSYNTHESIS produces oxygen in sunlight.

• RESPIRATION and BURNING FUELS use oxygen and produce carbon dioxide.

• Carbon dioxide is absorbed by the SEAS and OCEANS

Limestone, Thermal Decomposition and limewater

Calcium Carbonate CaCO3

Calcium Oxide CaO

Calcium hydroxide Ca(OH)2

It can be used as a neutralising agent.

It is used in glass making, cement making and in

the Blast furnace

It is decomposed by heat to form calcium oxide,

also known as quicklime.

When water is added to quicklime, slaked lime is

produced.

Both these products can be used to neutralise acid in soils.

When slaked lime is dissolved in water,

limewater is produced.

Limewater reacts with carbon dioxide to

form Calcium carbonate.

This is the test for Carbon dioxide.

Carbon dioxide CO2

Limestone is mainly Calcium Carbonate.

• Limestone is a sedimentary rock.

• It comes from the shells of sea creatures or from solids formed in the oceans long ago.

• It is mostly made of calcium carbonate - CaCO3.

• It is an important raw material for both the chemical and the construction industries.

Limestone

Limestone for soil

• Acidity can build up in soils.

• This can inhibit the growth of many crops. Consequently farmers need to adjust the pH back towards neutral.

• Limestone provides a cheap way of neutralising soil acidity.

Limestone is used in agriculture.

765pH

Limestone - extraction of iron

• Limestone is one of three major raw materials used to extract iron from its ores.

• It reacts with acidic impurities changing them into a slag that separates from the iron.

In the blast furnace limestone removes acidic earthy impurities that would ruin the quality of iron.

CaCO3 + SiO2 CaSiO3 + CO2

Quicklime - the lime kiln

• Limestone is heated in huge ovens known as lime kilns.

• The calcium carbonate decomposes into calcium oxide (quicklime) and carbon dioxide.

• Quicklime is a vital ingredient of cement, concrete and of most types of glass.

CaCO3 CaO + CO2

Slaked lime

• If water is added to quicklime the calcium oxide changes into calcium hydroxide (slaked lime).

• Slaked lime is a vital ingredient of various building materials.

CaO + H2O Ca(OH)2

• A solution of calcium hydroxide (limewater) is also used to test for carbon dioxide gas (it goes cloudy).

Manufacture of cement

• The main raw materials for cement are limestone and clay.

• A small amount of gypsum is also added to help the cement set at the right speed.

Clay or shale

Limestoneor chalk

Gypsum(calcium sulphate)

heatCement

Cement, concrete and mortar

• To make concrete cement is mixed with small stones or gravel.

• Mortar consists of cement mixed with calcium hydroxide. This makes a smooth slow setting mixture suitable for bricklaying

Cement, concrete and mortar all set when interlocking crystals grow between cement particles joining them together.

Manufacture of glass

Limestone, sand and sodium carbonate are the raw materials used to make most glass.

Limestone

Lime(calcium

hydroxide)

Sand (silicondioxide)

Sodiumcarbonate

heat

water

Glass

heat

Match it up