Revision Checklist C1a Crude Oil (a)
Crude oil is a fossil fuel and is non-renewable resource. It is a finite resource as it will run out one day if we continue to use them.
It is a mixture of hydrocarbons, separated by fractional distillation.
Distillation uses differences in boiling points. Larger hydrocarbons have stronger intermolecular forces and higher boiling points.
Hydrocarbons with highest boling point leave at bottom of column- Hydrocarbons with lowest boiling point reach top without cooling enough to condense leaving as gases.
Crude oil vapours must be cooled and condensed so they leave the fractuionating column as a liquid.
Substances leaving column called fractions.
Intermolecular bonds break during boiling but covalent bonds do not.
Revision Checklist C1a Crude Oil (b)
Impermeable rock trap oil so it cannot escape to surface.
Oil wells drilled to pump oil to surface and then transported to refineries
Exploiting crude oil can cause environmental problems (oil slicks etc)and associated with political problems(Middle East largest producers - USA and Europe largest consumers)
OIl producers decide to reduse supplies or raise prices - oil consumers cannot prevent this from happening
Crude oil paid for internationall in US dollars- variations in curency exchange rates
Pertochemicals= chemical obtained from crude oil.
Cracking = chemical process converts large hydrocarbon molecules into smaller more useful ones by heating oil fractions to high temp and passing them over a catalyst- this breaks down long chain alkanes into smaller molecules, including alkenes.
Cracking helps to match supply of fractions to demand such as petrol.
Revision Checklist C1a Crude Oil (c)
Alkanes = Octane and hexane= Saturated hydrocarbons that contain only single bonds- no rings or double bonds in its molecule.
Alkene = Ethane = used to make polymers= unstaurated hydrocarbons that contains a double bond(2 shared pairs of electrons) between two carbon atoms. C=C
Alkenes used in polymerisation reactions. Many small monomer molecules join to form one large polymer molecule.
Uses of polymer depend on its properties. Disposal of non-biogradable polymers can cause environmental problems.
Alkanes in crude oils are used as fuels- Equation for complete combustion is
hydrocarbon + oxygen --carbon dioxide + water. Heat energy is relaesed.
Burning hydrocardbon fuels releases carbon dioxide (greenhouse effect) Carbon monoxide (toxcic) Sulfur oxides and nitrogen oxides (acid rain) and particulates (global dimming)
Revision Checklist C1b - Burning hydrocarbons/Carb
Fuel = substance reacts with oxygen to release useful energy- mostly heat energy.
Combustion= Process of burning fossil fuels which release carbon dioxide into the atmosphere and provide energy.
Complete combustion happens when hydrocarbon chemical contain only hydrogen and carbon atoms. Plenty of air
hydrocarbon + oxygen ----- Carbon dioxide + water
Incomplete combustion =shortage of air = burning of a hydrocarbon to produce substances that could be oxidised further , such as carbon (soot) and carbon monoxide.
hydrocarbon + oxygen ---- carbon monoxide + carbon + water
Limewater = solution of calcium hydroxide in water.
& factors to consider choosing a fossil fuel ACEPETS
Availabilty, Cost,Energy value,Pollution, Ease of use, Toxicity, Storage
Revision Checklist C1c Clean Air
Earth is about 4.5 billion years old- Early atmosphere came from gases released from inside Earth's crust by volcanoes.
The Earth's atmosphere has a stable composition of oxygen,nitrogen, water and carbon dioxide
78% nitrogen and 21% oxygen Carbon dioxide 0.035%
The composition of the Earth's atmosphere has developed and changed due to : volcanic eruption, condensing of water, dissolving of gases in seas and photosynthesis.
Oxygen and nitrogen in the atmosphere have increased over time. Carbon dioxide, ammonia and methane decreased.
Ammonia broken down by sunlight by its reation with oxygen forms Nitrogen. Nitrogen is an unreactive gas so leevels increase in atmosphere.
Carbon dioxide soluble gas - large amount dissolve in the oceans
Revision Checklist C1c Air pollution
Carbon dioxide levels gradually increasing - due to respiration and use of fossil fuels.
Global warming - Human activities release carbon dioxide faster than it can be removed. Greater demand.
Deforestation - big impact on carbon dioxide levels - less photsythesis and burning land releases more carbon dioxide.
Pollutants = substances released into environment that damage living things including us.
Atmospheric pollutants released into the air. Vehicles reease large amounts - Catalytic converts fitted to cars convert carbon monoixde into carbon dioxide.
carbon monoxide + nitrogen oxide ------- nitrogen + carbon dioxide
2CO + 2NO ______ N + 2CO
Fossil fuels contain small amounts of sulphur compouns - theses form sulfur dioxide when fuel is burnt. This gas dissolves in water in clouds forming acids creating acid rain. Erodes stonework and corrodes metals. Kill trees and living things in lakes and rivers.
Carbon dioxide poisonous gas can cause sickness and death.
Revision Checklist C1d Alkanes and alkenes
Covalent bond is a shared pair of electrons
Alkanes = methane, ethane, propane, butane - carbon atoms joined by single covalent bonds
Saturated compound = compound contains no double bonds in its molecule = Alkanes
Alkenes = ethene, propene, butene = contain a double covalent bond between carbon atoms.
Unsaturated compound= Alkenes = compound that contains at least one dpouble bond in its molecules.
Bromine reacts with alkenes but NOT alkanes.
Bromite water is orange and turns colourless when mixed with alkenes but NOT when mixed with alkanes. Reaction between bromine and an alkene is an addition reaction used to test for unsaturation.
Revision Checklist C1 Making polymers
Polymer = Material whose molecules are made up of many repeated units = very large molecules in plastics
Monomer= Material whose molecules are the individual structural units of a polymer
Poly(ethene) polymer made from ethene monomers
Polymerisation = Reaction in which monomer molecules join together to make a polymer
Addition polymerisation= Polymerisation reaction that only involves addition reactions involving alkene monomers.
Addition reaction = Reaction in which two reactants combine to make one product.
Polymers poly(ethene), PVC and Teflon were all discovered by accident.
LEARN THE DISPLAYED FORMULA FOR A POLYMER
Revision Checklist C1e Designer polymers
Nylon used in clothing
Polymers are non-biodegradable (cannot be decomposed by bacterial action) and many are unreactive. KLandfill sites not popluar difficult to find new sites.
Cross-Link= Bond that links two polymer chains together- Plastics have high melting point, are rigid and cannot be easily stretched.
Laminated = Made up of layers joined together
Waterproof clothing stops water getting in but also stops sweat getting out.
Breathable clothes stops rain getting in and LETS sweat out
Polymers can be recycled eg PET used for drink bottles can be recycled to make fibres for clothes. Sorting difficult and expensive.
Chemists developing new types of biodegradable polymers, can be broken down by microorganisms. Some disolve in water eg dishwasher tablets covered in plastic.
Revision Checklist C1f Cooking
Chemical change happens if
a, new substance is made b,change is irrevesible c, energy change happens
Denatured = state of proteins that have had their structure altered by heating or by chemical treatment
Carbohydrate = compound , sugar or starch, that contains carbon hydrogen and oxygen with formula CH O
Starch = large carbohydrate molecules that are polymers of sugars
Chemical reactions during cooking produce new substances
Balanced equations describe what happens in reactions
Decomposition of sodium hydrogencarbonate.
2NaHCO -- Na CO + H O + CO
Sodium Sodium carbonate + Water + Carbon dioxide
Revision Checklist C1f Food Additives
Food Additives improve its properties. 4 main ones:
• Antioxidant stops food reacting with oxygen and going off i.e. Vitamin C
• Food colour = more attractive i.e. caramel
• Flavour enhancer = improves flavour i.e. monosodium glutamate
• Emulsifiers stop oil and water in food from separating i.e. egg yolk lecithin- improve texture of mayonnaise making it thicker.
Emulsifier molecules water loving part = hydrophilic end - oil loving part = hydrophobic end.
Revision Checklist C1g Smells
Ester = compound such as ethyl ethanoate (pear drop smell) made by treating organic acid with an alcohol
Alcohol + acid ----ester + water
Esters are used in perfumes, they evaporate easily and have pleasant smells and low boiling point.
Organic acid = Acid that has molecules containing a carbon chain
Synthetic = a substance that does not occur in nature made in lab.
Volatility = Ability of a substance to evaporate.
Revision Checklist C1g Nail varnish and testing
Solution = Mixture solvent (liquid) and solute (substance)
Solvent = Liquid that dissolves a substance to form a solution
Solute = Substance dissolved in liquid to form a solution.
Soluble = substance dissolves in liquid
Insoluble = substance will not dissolve in liquid.
For = Find new medicines and improve safety of medicines
Against = Expensive to look after animals and morally wrong.
Revision Checklist C1h Paints and pigments
Different solvents are used in paints and cosmetics to dissolve different solutes (varnish, pigment or oils)
Paint is a colloid (one substance dispersed in another) - Colloid different from solution as substances not dissolved they are dispersed evenly in another substance.
3 main ingredients = Pigment = gives paint colour - Binding medium + sticks pigments to surface - Solvent = thins paint so spreads more easily.
Pigments in paint can be made sensitive to light or heat
Phosphorescent = something that gives out light absorbed earlier- can glow in the dark
Thermochromic= substance that changes colour according to temperature - heat sensitive dyes mugs, bath toys, babies spoons
Radioactive= something that emits radiation from nucleus of an atom
Radiation = Transfer of energy across distance, sometimes in form of particles given off by the nuclei of radioactive atoms.
Radium is a radioactive metal - can damage cells and may cause cancer.