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The units in this module are:

C2a – Paints and Pigments

C2b – Construction Materials

C2c – Does the Earth move?

C2d – Metals and Alloys

C2e – Cars for Scrap

C2f – Clean Air

C2g – Faster or Slower 1

C2h – Faster or Slower 2

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What’s in a paint?

How paints dry

What is a colloid?

Thermochromic paints

Phosphorescent paints Main menu

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What’s in a paint?What’s in a paint?

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Paints have different ingredientsingredients in them to do different jobs

Reason Reason

Pigment To provide colour

Binding agent Keeps the paint attached to the surface

solvent Dissolves the pigment and binding agent

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How paints dryHow paints dry

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Water basedWater based paints such as emulsion paints dry because the solvent evaporatessolvent evaporates and forms a film

Oil basedOil based paints dry because the solvent evaporatessolvent evaporates and the binding agent reacts with oxygenoxygen and harden to form a film of paint

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What is a Colloid?What is a Colloid?

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Paint is a mixture called a colloidcolloid

A colloid is where solidsolid particles are mixed with liquidliquid particles but do not dissolvedo not dissolve.

The solid particles are disperseddispersed in the liquid.

They are so small that they do not settle on the bottom and stay mixed.

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Thermochromic paintsThermochromic paints

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There are some specialspecial types of paints available.

Some paints contain pigmentspigments that change colour as temperaturetemperature changes

These are called thermochromicthermochromic paints

Uses of these paints include: thermometers

cups

kettles

baby spoons

eggs

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Phosphorescent paintsPhosphorescent paints

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Some paints can glow in the darkglow in the dark.

They contain phosphorescent pigmentsphosphorescent pigments.

These pigments absorb and store lightlight energy.

Uses : dash boards

warning signs

Before phosphorescent pigment were used, radioactiveradioactive materials were used on watch faceswatch faces to make them glow

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For a paint you need a pigmentBlend the powder with an oil

Thin it with a little solventStir it well but do not boil

 Paint it on, this is your colloid

Let the solvent blow awayIt’s the same with an emulsion

Of two liquids, one will stay 

Left behind the binding mediumSticks the colour to the wall

Forms a smooth protective layerDoesn’t look too bad at all

 Dyes and paints can make a statement

Dress up as a ghost or spriteUse some paint that’s phosphorescent

Lit by day, it glows by night 

Choose a colour that’s syntheticIf you want to paint the town

Or wear the latest thermochromicHeat – or cold – will change it round

 

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Which materials are used?

Products from rocks

Using limestone

Making concrete

Problems with rocksMain menu

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Which materials are used?Which materials are used?

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Lots of materialsmaterials can be used in buildings

Some examples are : glass

bricks

steel

aluminium

wood

iron

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Products from rocksProducts from rocks

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Limestone, granite and marbleLimestone, granite and marble are three rocks which can be used as construction materials.

LimestoneLimestone Sedimentary rockMade by sea creatures sinking to the bottom of the sea and buried

GraniteGranite Igneous rockFormed when molten rock cools down

Marble Marble Metamorphic rockMade by action of heat and pressure on limestone

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Heating limestoneHeating limestone

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Limestone is calcium carbonate, CaCOcalcium carbonate, CaCO33

Heating limestone is a thermal decompositionthermal decomposition reaction.

Two new substance are made in this reaction

Calcium carbonate Calcium carbonate Calcium oxide + Carbon Calcium oxide + Carbon dioxidedioxide

CaCOCaCO33 CaO + CO CaO + CO22

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Making concreteMaking concrete

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A lot of limestone is made into cementcement. Limestone and clayclay are heated together.

ConcreteConcrete is a useful construction material. It is made from cement, sand, gravel and watercement, sand, gravel and water.

Concrete is not very strong unless it is reinforcedreinforced.

Putting steel rodssteel rods in concrete reinforces it.

This makes the beams strongerstronger and prevents its from crackingcracking.

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Problems with rocksProblems with rocks

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Obtaining rocks from a quarryquarry can cause environmentalenvironmental problems

They take up valuable land valuable land spacespace

They destroy landscapeslandscapes

Destroy the environmentenvironment of plants and animals

Increase dustdust and noisenoise levels

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Structure of the Earth

Plate tectonics

Evidence for plate tectonics

Subduction

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Structure of the EarthStructure of the Earth

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Crust is solid rocksolid rock

Mantle is molten rockmolten rock

Outer core is liquid iron and liquid iron and nickelnickel. It is very dense.

Inner core is solid iron and solid iron and nickelnickel. It is very dense.

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Plate tectonicsPlate tectonics

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The crust and the upper mantle is called the lithospherelithosphere. The lithosphere is made up of large sections called tectonic platestectonic plates.

These plates floatfloat on top of the mantle. They move a few few cmcm each year.

The liquid in the mantle can move because of convection convection currentscurrents and carry the plates with it.

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Evidence for plate tectonicsEvidence for plate tectonics

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Africa and South America look like they fit togetherfit together suggesting they were once joined.

FossilsFossils and rocksrocks have been found on both continents.

EarthquakesEarthquakes and volcanoesvolcanoes occur where plates meet.

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SubductionSubduction

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When an oceanicoceanic plate and a continentalcontinental plate collide, the oceanic plate is forced underneathunderneath the continental plate.

The oceanic plate meltsmelts in the magma.

This is called subductionsubduction.

The continental plate forms fold mountainsfold mountains.

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VolcanoesVolcanoes

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VolcanoesVolcanoes are formed where there are weaknesses in the Earth’s crust. Molten rock can make its way to the surface.

GeologistsGeologists study volcanoes.

People choose to live near volcanoes because the land is fertilefertile and lots of cropscrops can be grown.

There are two types of volcanic rock

Extrusive igneousExtrusive igneous rocks form outside the Earth and have small crystals

Intrusive igneousIntrusive igneous rocks form in side the Earth’s crust and have large crystalslarge crystals

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Extracting copper

Purifying copper

Alloys

Smart alloys

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Extracting CopperExtracting Copper

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Copper is a useful metal used in wireswires and pipespipes

Copper is extracted from its ore using displacementdisplacement with carbon.

This is because carbon is more reactivereactive than carbon

Copper oxide + Carbon Copper oxide + Carbon Copper + Carbon dioxide Copper + Carbon dioxide

2 CuO + C 2 CuO + C 2 Cu + CO 2 Cu + CO22

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Purifying copperPurifying copper

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Copper can be purified using electrolysiselectrolysis. It must be 99.9%99.9% pure to be used in wires.

Rods called electrodeselectrodes are placed in an electrolyteelectrolyte (copper sulphate)

Copper metal forms on the cathodecathode

CuCu2+2+ + 2e + 2e-- Cu Cu

Copper from the anodeanode becomes ions in solution

Cu – 2eCu – 2e-- Cu Cu2+2+

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AlloysAlloys

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An alloyalloy is a mixture of elements where at least one is a metalmetal.

Metals are more usefuluseful as alloys.

AlloyAlloy Main MetalMain Metal Use Use

Amalgam Mercury Tooth fillings

Brass Copper & Zinc Hinges, screws, instruments

Bronze Copper & Tin Statues

Solder Tin & Lead Joining metals, circuits

Steel Iron Car bodies, ships

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Smart AlloysSmart Alloys

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Smart alloys are also known as shape memory alloysshape memory alloys.

Shape memory alloys can return to their original shapeoriginal shape when put in hot waterhot water or an electric currentelectric current is passed through it.Uses of shape memory alloys are:

originally for military uses

medical uses

spectacle frames

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Corrosion of iron

Corrosion of aluminium

Properties of iron and aluminium

Car bodies

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Corrosion of IronCorrosion of Iron

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Iron is the only metal that rustsrusts.

Iron needs oxygenoxygen and waterwater to rust. Rusting is speeded up by salt watersalt water or acid rainacid rain.

Iron + Oxygen + Water Iron + Oxygen + Water Hydrated Iron Oxide Hydrated Iron Oxide

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Corrosion of AluminiumCorrosion of Aluminium

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Aluminium does not corrodenot corrode even in damp conditions.

This is because it forms a layerlayer of aluminium oxidealuminium oxide.

This prevents the surface from corroding.

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Properties of Iron and AluminiumProperties of Iron and Aluminium

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Property Property Iron Iron Aluminium Aluminium

Density Denser than steel Lees dense than iron

Magnetism Magnetic Not magnetic

Corrosion Rusts easily Does not corrode easily

Malleability Malleable Malleable

Conductivity Good conductor Good conductor

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Car BodiesCar Bodies

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Steel is used to make car bodiescar bodies. It is harderharder and strongerstronger than iron. It is also less likely to corrode than iron.

Stainless steel was used to make a car body. It is more expensiveexpensive than steel but did not rust.

Aluminium can be used instead of steel.

Aluminium cars are lighterlighter and give better fuel economybetter fuel economy. An aluminium frame also corrodes less,

However, repair costs are approximately 25% moremore than steel.

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Composition of air

Evolution of the atmosphere

Air pollutants

Controlling air pollution

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Composition of AirComposition of Air

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Air is a mixture of gases.

It is:- 78% nitrogennitrogen

21% oxygenoxygen

1% other gasesother gases

The other gases include carboncarbon dioxide, water vapour dioxide, water vapour and argonand argon.

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Evolution of the AtmosphereEvolution of the Atmosphere

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The atmosphere has remained constantconstant for millions of years.

Atmosphere formed from volcanicvolcanic eruptions was made of carbon carbon dioxide, water vapour, methane dioxide, water vapour, methane and ammoniaand ammonia.

Water vapour cooledcooled and formed oceansoceans.

PlantsPlants form and convert carbon dioxide into carbon dioxide into oxygenoxygen

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Air PollutantsAir Pollutants

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PollutantPollutant How is it formed?How is it formed? ProblemProblem

Carbon Carbon monoxidemonoxide

Formed from incomplete

combustion in car engines

Is a poison and prevents oxygen transport around

body

Nitrogen Nitrogen oxidesoxides

In car engines from the reaction of

nitrogen with oxygen

Creates smog, acid rain and breathing

problems

Sulphur Sulphur dioxidedioxide

Combustion of fossil fuels containing sulphur e.g. coal

Acid rain

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Controlling Air PollutionControlling Air Pollution

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The balancebalance between carbon dioxide and oxygen can be changedchanged by humans

Increasing energyenergy use means more carbon dioxide

PopulationPopulation increase means more carbon dioxide

DeforestationDeforestation means more carbon dioxide

Catalytic convertersCatalytic converters can be fitted to car exhaust systems to change poisonous carbon monoxidecarbon monoxide and nitrogen nitrogen oxidesoxides into carbon dioxidecarbon dioxide and nitrogennitrogen.

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What are rates?

Measuring rates

Rates and graphs

Temperature and rates

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What are Rates?What are Rates?

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Chemical reactions are differentdifferent. The rate of reactionrate of reaction is the time it takes for a reaction to complete.

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Measuring RatesMeasuring Rates

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We can measuremeasure the rate of reaction by timing how longhow long it takes for a product to formproduct to form (e.g. a gas) or a reactant to reactant to be used upbe used up (e.g. a solid)

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Rates and GraphsRates and Graphs

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The graph starts steeplysteeply. This is when the reaction is fastest. When the line is flat, the reaction has stoppedstopped.

We can compare two reactions. The one with the steepest linesteepest line is the quickestquickest reaction.

We can calculate initial rateinitial rate of reaction by working out the gradient = volume of volume of gas(cmgas(cm33))

time(s)time(s)

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Temperature and RatesTemperature and Rates

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Particles of reactants must collidecollide for a reaction to occur.

As the temperature is increasedincreased the particles move fasterfaster because they have more energymore energy.

This means the particles collide more oftenmore often and with enough energyenergy. More collisions mean a faster reaction.

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Concentration and RatesConcentration and Rates

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As the concentration is increasedincreased there are more more particlesparticles in a given volume.

The particles are closercloser together

There will be more collisionsmore collisions and the reaction will be faster.

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Surface area and rates

Catalysts and rates

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Surface Area and RatesSurface Area and Rates

If we break up a solid reactantsolid reactant into smaller piecessmaller pieces, we increase the surface area.

Because more surface area is exposed, the particles collide more frequentlymore frequently.

More collisions mean a faster reaction.

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Catalysts and RatesCatalysts and Rates

Catalysts are chemicals which speed upspeed up a chemical reaction.

They are not used upnot used up during a reaction and do not change how much product is made, they just make it happen happen fasterfaster.

Catalyst are specificspecific – each catalyst only works for certain reactions

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