Highfields School 1 RED 2013

C1 - Carbon chemistry

Highfields School

Highfields School 2 RED 2013

1 Fossil fuels1.1 Fossil fuels

Fossil fuels are coal, oil and gas

Fossil fuels are non-renewable - they are nolonger being made or are being made muchmore slowly than they are being used up

� Fossil fuels are finite resources - there is only somuch available�� Factors to consider when selecting a fuel;-

1) energy value (how much energy per kg)2) availability3) storage4) cost5) toxicity (is it harmful)6) pollution (acid rain, greenhouse effect)7) ease of use

HT More fossil fuels being burnt as:- a) population increasing

b) growth of developing countries

1.2 Crude oil

Crude oil is a mixture of hydrocarbons

Mixture in crude oil is separated intofractions by fractional distillation

Each fraction contains many substances withsimilar boiling pointsHydrocarbons

are molecules with carbon and hydrogenatoms only

1.3 How fractional distillationworks

1. crude oil is heated

2. the fractionating column gets cooler as you go up

3. lower the boiling point - higher up the column thefractions come out

4. higher the boiling point - lower down the columnthe fractions come out

HT only

� Large molecules have high boiling points as theyhave stronger intermolecular forces holding onemolecule to another

When a substance boils, the forces betweenmolecules (intermolecular forces) are broken

but the covalent bonds within each molecule(intramolecular bonds) are not broken

1.4 Problems with crude oil

� Crude oil can spill when being transportede.g. by oil tanker or if an oil rig leaks

� Crude oil damages bird feathers causingdeath

Detergents usedto clean up oilslicks damageswildlife

HT only

UK depends on importing oil frompolitically unstable countries - could bedifficulties getting supplies in future

Eventually all the readily extractable crudeoil will be used up so replacements will beneeded

Crude oil is not only a fuel - also used tomake many petrochemicals

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1.5 Cracking large hydrocarbon molecules

� Cracking breaks large alkane molecules into smaller alkane and alkenemolecules

Alkanes - hydrocarbons with single C-C bonds only

Alkenes - hydrocarbons with a double C=C bond

Cracking in the laboratory

large alkane molecule

smaller alkenemolecule

smaller alkanemolecule

Cracking

allows oil refineries to

match the supply of useful

products with demand

Alkenemolecules can be used to

make polymers (plastics)

1.6 Burning fuels

Burning a hydrocarbon fuel in a plentiful supply of oxygen produces heat energy, carbon dioxideand water e.g.

propane + oxygen water + carbon dioxide + heat energy

HT only: C3H8 + 5O2 4H2O + 3CO2 + heat energy

� Complete combustion - plenty of oxygenpresent so water and carbon dioxide formed

� Experiment to show water and carbon dioxideformed:-

cobalt chloride paper turns from blue to pink if water is present

limewater turns cloudy if carbon dioxide is present

Cracking needs a catalyst and ahigh temperature

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1.7 Incomplete combustion

� Incomplete combustion - there is not enoughoxygen to burn the fuel completely.

� Less energy is released compared to completecombustion

� Instead of carbon dioxide, carbon monoxide isformed e.g.

methane + oxygen water + carbon monoxide

CH4 + 1.5 O2 2 H2O + CO

Carbon monoxide is a poisonous gas

Blue (hotter) bunsen flame is completecombustion. Yellow bunsen flame isincomplete combustion

� If there is even less oxygen, carbon (soot) isproduced e.g

methane + oxygen water + carbon

CH4 + O2 2H2O + C

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2 Clean air2.1 The atmosphere

�

2.2 History of the atmosphere

Original atmosphere came from gasesescaping from the interior of the Earth

� Photosynthesis by plants increased thepercentage of oxygen to today’s level

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Degassing of early volcanoes producedatmosphere rich in water and carbondioxide

Water condensed into oceans

� Carbon dioxide dissolved in the oceans

As water and carbon dioxide removed,nitrogen became bigger percentage

Photosynthesis resulted in increased oxygen

2.3 Atmospheric pollution

Important that air pollution is controlled- damages our surroundings and health

� Carbon monoxide - poisonous gas, fromincomplete combustion petrol/diesel�

Oxides of nitrogen - high temperature ininternal combustion engine allows nitrogen toreact with oxygen. Causes photochemicalsmog and acid rain.

Sulfur dioxide - sulfur imputities in fossilfuels react with oxygen. Causes acid rain(kills plants and aquatic life, erodes

stonework and corrodes metals)

2.4 Catalytic converters

Catalytic converters in cars- changecarbon monoxide into carbon dioxide

2CO + 2NO N2 + CO2

HT only - 2.5 Human influence on the air

� Deforestation - less photosynthesis and wood burning, both result in increase carbon dioxide

Increased human population - more pollutants and more carbon dioxide released

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2.6 The carbon cycle

Carbon cycles between the atmosphere and living things through photosynthesis,respiration and combustion

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3.1 Polymers

Polymers are large molecules made when many monomers (small molecules) join together (in apolymerisation reaction)

Polymer is named by putting ‘poly’ in front of the monomer name and putting the monomer inbrackets e.g. ethene makes poly(ethene), propene makes poly(propene)

3 Polymers

3.2 Alkanes

Displayed formula - shows atoms andbonds

� Molecular formula - shows atoms

Alkanes - saturated compounds (singlecovalent bonds only), general formulaCnH2n+2

3.3 Alkenes

Alkenes - unsaturated compounds(have a double bond), general formula

CnH2n

Double bond contains 2 shared pairs ofelectrons

Bromine water - test for double bonds. Ifdouble bond present, bromine water changesfrom orange to colourless

HT only

Alkene + bromine is an addition reactionas the bromine adds to the double bond toform a dibromo compound (compound

with 2 bromine atoms)

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3.4 Making polymers(polymerisation)

� High pressure and a catalyst are needed toforce monomers to join together to make apolymer

� To make poly(ethene):-

�

� The polymerisation can also be shown by using nfor a large number and putting the repeating unit inbrackets

3.5 Polymerisation (HT only)

� If you know the displayed formula of themonomer, you can draw the displayed formulaof the polymer:-

(remember, the double bond disappears)

� You can also draw the monomer from thepolymer:-

(remember to put the double bond in the monomer)

3.6 Properties of polymers

Different polymers have different properties, making them suitable for different jobs

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The atoms within a polymer chain are held together by strong covalent bonds

The intermolecular forces between polymer chains can be strong or weak:-

Weak intermolecular forces Strong intermolecular forces

Lowmelting point, stretched easily

(as chains can slide)

Highmelting point, cannot bestretched, rigid (as chains

can’t slide)

Strong intermolecular attraction

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3.7 Nylon and Goretex

Nylon is used in clothes

Nylon is tough, lightweight and keeps waterand UV light out

� Nylon does not ‘breathe’ - it doesn’t let watervapour out

Goretex has the same advantages as nylon but isalso breathable (lets perspiration out)

� Breathable materials help prevent active outdoorpeople being soaked with condensed perspiration

HT only

Goretex is nylon laminated with a PTFEmembrane - the membrane has holes which aretoo small to let water drops through but largeenough to let water molecules through

3.8 More designer polymers

� Chemists are developing new polymers

Soluble polymers - polymers that dissolve inwater. Used as wrapper for dishwasher tabletsand for bags for hospital bedding as theworkers don’t have to handle the bedding whenputting it in the washing machine - less risk ofinfection. Also make disposal easy.

� Biodegradable polymers - polymers thatbacteria can break down, helps to reduce litterand reduces the problem of how to dispose ofplastics

3.9 Disposal of plastics

� Many different types of plastic - most arenon-biodegradable so will not rot.

Most plastics are made from crude oil which isrunning out - so plastics are a valuableresource

Landfill - puttingplastic into holesin the ground -uses up land andwastes resources

Burning plastics - produces air pollution andsome plastics produce toxic fumes. Alsowastes resources

Recycling - prevents waste of resources.Plastics need to be sorted - difficult and time-consuming so expensive

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4 Cooking and food additives4.1 Cooking

Cooking is a chemical change as:-

a new substance is formed

the process cannot be reversed

(an energy change also shows a chemical reaction has taken place)

Cooking proteins (eggs and meat) changes theshape of the protein molecules (calleddenaturing)

�

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� Cooked potato is easier to digest as:-

cell walls rupture (break) so no longer rigid, softer texture

starch grains swell up and spread out

4.2 Emulsifiers

Emulsifiers - substances that help oil andwater mix

Emulsifier molecules have a water loving(hydrophilic) part and an oil or fat loving(hydrophobic) part

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Hydrophilic end bonds to water molecules,hydrophobic end bonds to oil/fat molecules

� This stops the oil and water separating into 2layers

(protein is denatured)

heat

4.3 Baking soda - sodium hydrogen carbonate

When baking powder is heated, it breaks down to release carbon dioxide. The carbon dioxide gasmakes cakes rise

� The equation for the thermal decomposition of baking soda is:-

sodium hydrogen carbonate sodium carbonate + carbon dioxide + water

2NaHCO3 Na2CO3 + CO2 + H2O

Test forcarbon dioxide - bubble

gas through limewater,limewater goes cloudy

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5 Smells - perfumes and esters

4.4 Food additives

� Antoxidants stop food reacting with oxygen

� Food colours give food an improved colour

� Flavour enhancers improve the flavour

� Emulsifiers help oil and water to mix and not separate

5.1 Perfumes

Cosmetics can be natural or synthetic(man made)

Esters are perfumes that can be madesynthetically

� Esters are made by:-

alcohol + acid ester + water

A perfume needs to:-

1. evaporate easily (so perfume particlesreach the nose)

2. non-toxic (so doesn’t poison you)

3. not react with water (otherwise wouldreact with perspiration)

4. does not irritate the skin

5. insoluble in water (so doesn’t washoff)

HT only

� To evaporate, particles need enough energy toovercome the attraction to other particles

� Only weak attractions between perfume particles, so can evaporate easily

5.2 Solutions

Solvent - liquid in which the solute dissolvesto make a solution

� Solute - the substance that dissolves in thesolvent

� Solution - mixture of solvent and solute thatdoes not separate out

HT only

� Water will not dissolve nail varnish coloursas water molecules attract each other morethan they attract nail varnish particles

and

nail varnish particles attract each other more than they are attracted to water

5.3 Testing cosmetics

� Testing of cosmetics on animals is bannedin the EU - cruel to animals and animalsreact differently to humans

New cosmetics have to be thoroughly testedto make sure they don’t harm humans

HT only

� People have different opinions about testingcosmetics on animals - either it is cruel toanimals and there are better alternatives or it isnecessary to prevents humans being harmed

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6 Paint6.1 Paint

3 parts of a paint;-

1) Solvent - thins paint, easier to spread

2) Binding medium - sticks pigment to surface

3) Pigment - gives colour

Emulsion paints - water based paints that drywhen the water evaporates

Oil paints - pigmentdispersed (spread out) inoil and often have a solventthat dissolves oil

Paint is a colloid - solidpigment particles arespread out in a liquid but they are notdissolved

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� Oil paints dry as the solvent evaporatesand the oil is oxidised by atmosphericoxygen

Colloid particles must be very small sothey don’t settle to the bottom (collisions

with the liquid particles keep themfrom settling)

Topic

1 Fossil fuels L K J2 Clean air L K J3 Polymers L K J4 Cooking and foodadditives L K J5 Smells - perfumesand esters L K J6 Paints L K J

6.2 Thermochromic paints

Thermochromic pigments change colourwhen heated or cooled

� Useful to make sure liquids are not too hote.g. mugs, baby feeding spoons, bath toys

HT only - if a thermochromic pigment goescolourless at a particular temperature, can mixthe thermochromic pigment with acolouredacrylic paint.When thethermochromicpigment goescolourless, theacrylic paintcolour is seen

6.3 Phosphorescent paints

� Phosphorescent pigments - glow in the darkpigments. They store energy and release it aslight energy over a period of time

HT only - early glow in the dark paints wereradioactive - harmed workers who paintedwith them (e.g. caused cancer) so nowreplaced by the much safer phosphorescentpaints