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Unit 2

Everyday Chemistry

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Menu

To work through a topic click onthe title.

Metals

Personal Needs

Fuels

Plastics

End

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Metals

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Finding Metals

Most metals are found combinedwith other elements.

These compounds are called ores. Some metals, including gold, silver

and copper, are found uncombined

in the Earth's crust. This meansthat we can find the element on itsown.

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Extracting Metals

We get somemetals, including

iron, from theirores by heatingthe ore withcarbon.

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We get somemetals, including

aluminium, fromtheir ores usingelectricity.

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Using Metals

The propertiesof metals are thethings it can do and the way it

acts. Metals are chosen for certain uses

because of their properties.

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Densityof a metal is a measure ofhow heavy it is, compared to its

volume. That is why lead weights are used

for fishing lines.

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All metals are good conductors ofheat i.e. they have a high thermal

conductivity. That is why metals are used for

making pots and pans, radiators

etc.

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All metals are good conductors ofelectricity i.e. they have a high

electrical conductivity. That is why metals are used for

making electrical wiring etc.

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Metals are malleable. This meansthat they are easily made into new

shapes. This property is used when metals

are made into a variety of objects,

such as fencing, horse shoes etc.

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Metals are strong.

Metals are used to make many

things because of this strength e.g.car bodies, girders, tools etc.

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Alloys

An alloy is a mixture of metals, orof metals with non-metals.

Many alloys have important uses.

Examples of alloys are:

brass

solder

'stainless' steel

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Reactions of Metals

Metals react with many differentmaterials.

By comparing reactions and seeingthe differences between them wecan recognise the reactivity of

different metals.

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Metals react with oxygen toproduce metal oxides.

Magnesium + Oxygen Magnesium oxide

Aluminium + Oxygen Aluminium oxide

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Some metals react with water toproduce hydrogen.

Sodium + Water Sodium hydroxide + Hydrogen

Potassium + Water Potassium hydroxide + Hydrogen

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Many metals react with dilute acidto produce hydrogen.

Some metals, including copper,silverand gold, do not react withdilute acid.

Zinc + Hydrochloric acid Zinc chloride + Hydrogen

Iron + Sulphuric acid Iron sulphate + Hydrogen

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Test for hydrogen

The test for hydrogen is that itburns with a 'pop'.

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Corrosion

Corrosionis a chemical reaction.

In corrosion the surface of a metal

changing from an element to acompound.

For corrosion to take place the

metal must react with somethingin its surroundings.

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Rusting

Rustingis the corrosion of iron.

Rusting results the iron object

becoming weaker.

Both oxygen(from the air) andwaterare required for rusting.

Rust indicatorcan be used to showthe extent of the rusting process.

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Acid rainincreases the rate ofcorrosion.

Salt spread on roads increases therate of corrosion on car bodywork.

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Preventing Corrosion

Physical protectionpreventscorrosion by making a surface

barrier to air and water.

Now the metal cannot corrodebecause air and/or water cannot

get at the metal.

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Physical protection

Physical protection can be provided by:

Painting

Greasing Electroplating

Galvanising

Tin-plating Coating with plastic

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Chemical protectionpreventscorrosion by using chemicals.

Air and water can still get at themetal, but the chemicals preventcorrosion taking place.

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Chemical protection

Chemical protection can be provided by:

Iron does not rust when attached to

more reactive metals so zinc(galvanising) and scrap magnesium areused to protect iron.

Anodising is a process which increases

the thickness of the oxide layer onaluminium to provide protection againstcorrosion.

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Batteries

In a battery, electricity comes froma chemical reaction.

Batteries require to be replaceddue to the chemicals being used upin the reaction.

Examples of rechargeable batteriesinclude the lead-acid battery andthe nickel-cadmium battery.

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Cells

Electricity can be produced byconnecting different metals together,with a solution containing ions, to forma cell.

The ion solution completes the circuit.

The voltage between different pairs ofmetals varies.

The size of the voltage depends on thedifference in reactivity of the metals.

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Metals

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Personal Needs

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Keeping clean

When cleaning hair, skin andclothes the main problem isoiland

grease. This is because oil and grease do

not dissolve in water.

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Cleaning chemicals are required tobreak up the oil and grease into

tiny droplets These droplets can then mix with

water

This happens because cleaningchemicals dissolve in both waterand oil and grease.

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Some manufactured productscontain cleaning chemicals.

Some are :

Soaps

Detergents

Shampoos

Washing-up liquids and powders.

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Some soaps form a scumwith hardwater.

Soapless detergentsare used toform a lather with hard water.

Dry-cleaning uses special solvents

which are particularly good atdissolving oil and grease stains.

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Clothing

Clothing fabrics are made fromthin strands called fibres.

Fibres are made up of long chainmolecules called polymers.

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Natural fibrescome from plantsand animals.

Some natural fibres are:

silk

wool

cotton

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Synthetic fibresare made by thechemical industry.

Some synthetic fibres are

Nylon

Polyesters(e.g. Terylene)

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Synthetic fibres can be used tomake fabrics which have particular

uses. Dyesare coloured compounds,

which are used to give bright

colours to clothing.

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Chemists have developed ways oftreating fabrics to improve their

properties. Some fibres form strong bonds with

water molecules

These fibres are hard to drip-dry but

they do not feel 'sweaty' to wearbecause they soak-up perspiration.

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Personal Needs

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Fuels

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Fire

A fuelis achemical, which isburned to

produce energy.

When a substanceburns it reactswith oxygen.

Combustionisanother word forburning.

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A fire needs:

Fuel

Oxygen (usuallyfrom the air)

A temperature highenough to start thefire and keep it going

Take away anyone ofthe three and the firegoes out.

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Putting out fire

Fire-fighting methods in the laband the home include using

Fire blanket Sand

Water

Carbon dioxide gas

Foam.

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Different methodsof putting out the

fire are used indifferentsituations.

Water must not

be used with oil,petrol andelectrical fires.

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Fossil fuels

Fossil fuelsareformed from animaland plant remains

over a very longperiod of time.

Fossil fuels include

Coal

Natural gas

Oil

Peat.

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Finite Resources

Fossil fuels are finiteresources, i.e. theycannot be replaced.

If we use too muchof the fossil fuels afuel crisis will result,when most of the

fossil fuels havebeen used up.

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Hydrocarbons

The compounds, which are found infossil fuels are mainly hydrocarbons.

A hydrocarbon is a compound whichcontains hydrogen and carbon only.

Hydrocarbons burn in a plentiful supplyof air to produce carbon dioxide and

water. Hydrocarbon + Oxygen Carbon Dioxide + Water

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Renewable resources

Renewable resources are energyresources which can be replaced.

Some renewable sources of energyare:

Methane

Ethanol

Hydrogen

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Methaneis found in biogas, whichis made by the breaking down of

waste plant material. Ethanolis made from sugar cane

and can be mixed with petrol tomake a fuel for cars,

Hydrogen, which can be made fromwater, is a likely fuel for the future.

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Fractional Distillation

Crude oilis a mixture ofhydrocarbons.

A fractionis a group ofhydrocarbons with boiling pointswithin a given range.

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Fractionaldistillationis theprocess whichseparates crudeoil into differentfractions

according to theirboiling points.

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Fractions

Hydrocarbonsmade of smallmolecules boil

more easily thanhydrocarbonsmade of largemolecules.

Different fractionsare used asdifferent fuels.

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The uses of the fractions is decidedby their properties.

How easy it is to make them turninto a gas (evaporate)

Their thickness (viscosity)

How easy they are to burn(flammability)

Their boiling point range

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Cracking

Fractional distillation of crude oilgives more long chain

hydrocarbons than are needed. Crackingis an industrial method

for producing a mixture of smaller,

more useful molecules.

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Water Pollution

Oil spillages cancause greatdamage to marinelife and theenvironment.

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Air Pollution

Soot(carbon) and carbonmonoxide, a poisonous gas, can be

produced when hydrocarbons burnin a low supply of oxygen.

The burning of some fuels releases

sulphur dioxide, a poisonous gas,into the atmosphere.

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Nitrogen and oxygen from the aircan react inside a car engine to

form nitrogen dioxidewhich is apoisonous gas.

Leadcompounds which used to beadded to petrol cause pollution.

Benzenefumes in unleaded petrolare toxic.

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Fuels

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Plastics

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Plastics

Plastics are synthetic materials, i.e.made by the chemical industry.

Most plastics are made from oil. Examples of plastics include polythene,

polystyrene, perspex, PVC, nylon,Kevlar, bakelite, formica and silicones.

The properties of plastic help to decidewhat they are used for.

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Advantages and

disadvantages of plastics

For some uses, plastics haveadvantages over natural materials

and vice versa.

Biodegradablematerials arebroken down by bacteria in the soil

and rot away.

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Most plastics are notbiodegradable and their durability

and lightness can causeenvironmental problems.

Some degradable plastics have

been developed by chemists toease the problems of plastic waste.

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Recycling plastics

Since oil is a finite resource,recyclingis to be encouraged and

chemists are looking for renewablesources of plastics.

Recycling can be difficult because

of the many different kinds ofplastic in common use.

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Different plastics

Plastics can be either thermoplasticorthermosetting.

A thermoplastic is one which can bereshaped on heating.

A thermosetting plastic cannot bereshaped by heating.

The uses of thermosetting plastics aredecided by their heat and electricalinsulation properties.

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Making plastics

Plastics are madeup of polymers.

These are verylong molecules,made by joiningtogether many

small molecules.

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Polymer molecules are made from manysmall molecules called monomers.

The process of making a polymer byjoining many monomers together iscalled polymerisation.

Ethene monomers form poly(ethene),

also called polythene; the styrenemonomers form poly(styrene).

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Plastics

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The End

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