AQA Chemistry Unit 1AQA Chemistry Unit 1
This PowerPoint supports section C1.4, C1.5, C1.6 and C1.7 sections of the AQA Chemistry Unit 1
module
Crude OilCrude Oil
Hydrocarbons and crude Hydrocarbons and crude oiloil
Longer chains
mean…
1. Less ability to
flow
2. Less flammable
3. Less volatile
4. Higher boiling
point
Incre
asin
g le
ng
th
Crude oil is a mixture of HYDROCARBONS (compounds made up of carbon and hydrogen). Some examples:
Ethane
C C
HH
H
HH
H
Butane
C C
HH H
HH
H C C H
H
HH
Distillation revisionDistillation revision
This apparatus can be used to separate water and ink because they have different _____ ______. The ______ will evaporate first, turn back into a _______ in the condenser and collect in the _______. The ink remains in the round flask, as long as the _______ does not exceed ink’s boiling point. This method can be used to separate crude oil.
Words – temperature, boiling points, water, beaker, liquid
Fractional distillationFractional distillationCrude oil can be separated by fractional distillation. The oil is evaporated and the hydrocarbon chains of different lengths condense at different temperatures:
Fractions with low boiling points condense at the top
Fractions with high boiling points condense at the bottom
AlkanesAlkanesAlkanes are SATURATED HYDROCARBONS. What does this mean?
HYDROCARBONS are molecules that are made up of hydrogen and carbon atoms
SATURATED means that all of these atoms are held together by single COVALENT bonds, for example:
Ethane
Alkanes are fairly unreactive (but they do burn well). The general formula for an alkane is CnH2n+2
C C
HH
H
HH
H
Butane
C C
HH H
HH
H C C H
H
HH
General Formulae for General Formulae for AlkanesAlkanesInstead of circles, let’s use letters…
General formula for alkanes = CnH2n+2
Butane (n=4)
H
C C
H
HH
H
C C
H
HH
H H
Methane (n=1)
H
C H
H
H
Ethane (n=2)
H
H
C C
H
HH
H
Propane (n=3)
H
C H
H
H
C C
H
HH
H
Burning Fossil FuelsBurning Fossil FuelsBurning fossil fuels like oil and coal causes pollution.
Oil contains carbon:
C
H
H
H
HO
O
OO
OH H
OH H
CO
O
Carbon dioxide is a “greenhouse gas” – it helps cause global warming
Coal contains carbon, sulfur and other particles:
sulfur + oxygen sulfur dioxide
Sulfur dioxide causes acid rain. Other particles can cause “global dimming” – sunlight is absorbed by the particles in the atmosphere.
Removing SulfurRemoving SulfurSulfur dioxide is clearly bad for the environment so it’s a good idea to remove as much sulfur as possible:
Vehicles can remove sulfur from fuels before they are burned.
Power stations can remove sulfur dioxide from waste gases after combustion.
Other fuel sourcesOther fuel sources
Task: Identify two other fuel sources (“biofuels”) currently being developed and find out the following:
1) What is the source called and what is it made of?
2) Why is the fuel better than coal?
3) What are the disadvantages of this fuel?
Using Crude OilUsing Crude Oil
Crude Oil
Benefits Drawbacks
Cheap to extract
Wide range of uses as fuel
Used to make plastics
Plastics don’t
biodegradeBurning
fossil fuels causes
pollution
Disposal of materials uses up land fill
sites
It’s going to run out
Disposal of plasticsDisposal of plastics1) Landfill sites - most plastics do not _________ which means that landfill sites are quickly filled up. Research is being carried out on __________ plastics.
2) Burning – this releases carbon dioxide which causes the ________ effect, as well as other ________ gases.
3) _______ – the best option, but difficult because of the different types of plastic
Words – recycling, greenhouse, decompose, biodegradable, poisonous
EthanolEthanolEthanol is an important chemical. Many countries are increasing the amount of ethanol put into their petrol supplies:
Ethanol is a “clean burning” energy source and produces little or no greenhouse gases. How is it made and what are the advantages and disadvanatges of each method?
Ford Escape E85 – runs on 85% ethanol
The “fossil fuel” way
The “renewable” way
Ethene + steam ethanol
Ethene is produced by “cracking” oil
Sugar ethanol + carbon dioxide
Sugar is produced from standard crops like sugar cane and corn
Making ethanol from Making ethanol from etheneethene
Ethene
Reaction vessel with high temperature and pressure
and a catalystEthanol
Unused ethene recycled
Ethene + water ethanol
C2H + H20 C2H5OH
CrackingCrackingShorter chain hydrocarbons are in greater demand because they burn easier. They can be made from long chain hydrocarbons by “cracking”:
Butane
Ethane
For example, this bond can be “cracked” to give these:
Ethene
CrackingCracking
This is a THERMAL DECOMPOSITION reaction, with clay used as a catalyst
1) Carbon dioxide causes the _________ effect
2) Sulfur dioxide causes _____ _____
3) Plastics are not _____________
Cracking is used to produce plastics such as polymers and polyethanes. The waste products from this reaction include carbon dioxide, sulfur dioxide and water vapour. There are three main environmental problems here:
Long chain hydrocarbon
Heated catalyst
Gaseous hydrocarbon
Liquid hydrocarbon
AlkenesAlkenesAlkenes are different to alkanes; they contain DOUBLE COVALENT bonds. For example:
Ethane Ethene
Butane Butene
This double bond means that alkenes have the potential to join with other molecules – this make them REACTIVE. Alkenes turn bromine water colourless.
ALK
AN
ES
ALK
EN
ES
Testing for alkenesTesting for alkenes
Oil Bromine goes colourless
Bromine water
General Formulae for General Formulae for AlkenesAlkenes
General formula for alkenes = CnH2n
Propene (n=3)
H
C H
H
H
C C
H
H
Ethene (n=2)
H
H
C C
H
H
Butene (n=4)
H
C C
H
HH
H
C C
H
H H
Monomers and PolymersMonomers and Polymers
C CHH
HH
Ethene
Here’s ethene again. Ethene is called a MONOMER because it is just one small molecule. We can use ethene to make plastics…
Step 1: Break the double bond
Step 2: Add the molecules together:
This molecule is called POLYETHENE, and the process that made it is called POLYMERISATION
Another way of drawing it…Another way of drawing it…Instead of circles, let’s use letters…
Ethene
C C
HH
HH
C C
HH
HH
Ethene
H
C C
H
HH
H
C C
H
HH
Poly(e)thene
General formula for addition polymerisation:
C Cn C C
n
e.g. C Cn
H CH3
HH
C Cn
H CH3
HH
Some examplesSome examples
C Cn
H H
HH
C Cn
H H
HCl
C CnH H
HH
C CnH H
HCl
C CnH Cl
HBr
C Cn
H Cl
HBr
Uses of addition polymersUses of addition polymersPoly(ethene) Poly(propene)
Poly(chloroethene), PVC
Poly(styrene)
Biodegradable carrier bagsBiodegradable carrier bags
This carrier bag has been made with flax fibre from industrial waste.
Measuring Energy in FoodMeasuring Energy in Food
The energy content in foods is measured in Joules and calories
Foods with large carbohydrate and fat contents have lots of energy, but too much energy and too little exercise could lead to obesity.
Vegetable OilsVegetable Oils
Use of oil Benefits Drawbacks
Oily foods
Fuel
When plants photosynthesise they produce glucose. They can also produce vegetable oils and we can use these for food and fuel:
Extracting OilExtracting Oil
Step 1: Crush the plant
Step 2: Remove oil by pressing
OR step 3: Remove oil by distillation
Why use oil for cooking?Why use oil for cooking?1) Why do we use oil for cooking and not just water?
2) What are the problems associated with using oil in cooking?
Healthy and Unhealthy OilsHealthy and Unhealthy OilsUnhealthy oils:
Healthy oils:
“Saturated”
“Unsaturated”
Saturated vs. Unsaturated Saturated vs. Unsaturated FatsFats
Some oils are more healthy than others. Fish oils contain the nutrients Omega-3 and Omega-6. These oils are “unsaturated” like ethene:
C CHH
HH
Ethene
Testing for double bonds:
Clearly, it is important for scientists to be able to test if a food contains “healthy” unsaturated fats or “unhealthy” saturated fats. Here’s how it’s done:
Oil (in ethanol)Bromine goes colourless
Bromine water
Turning unsaturates into Turning unsaturates into saturatessaturates
The unsaturated fat is hardened by “hydrogenation”. Hydrogenated oils have a higher melting point and so are solid at room temperature, making them useful for spreads and pastries.
600C, Nickel catalyst
EmulsionsEmulsionsWhat’s an emulsion?
It’s a mixture of oil and water, like in salad dressing…
Paint is an emulsion. Other examples:
Milk Cream Butter
Butterfat
Watery liquid
Why use emulsions?Why use emulsions?Emulsions can have varying textures and this makes them useful. Some examples:
Different thicknesses
of cream
Paint and mayonnaise
EmulsifiersEmulsifiersAn emulsifier is an additive that will stop oil and water from seperating, like in mayonnaise.How they work:
Water Oil
I’m an emulsifier – I’ll sort this out with my hydrophobic end and my hydrophilic end!
I don’t want to mix with you!
The water and oil drops become “coated” and insulated from one another, which prevents them from separating.
Uses of emulsifiers in foodUses of emulsifiers in food
Emulsifiers are used:
1) In bread, to stop large _____ developing when it bakes
2) In low fat spreads, to allow the oil and water to be _____
3) In ice cream and spray cream, to ______ the foam
4) In sponge cakes, to make tiny pockets of ____
5) In chocolate, to stop melted chocolate forming _______
Words – crystals, air, holes, mixed, stabilise
The Structure of the EarthThe Structure of the EarthA thin crust - 10-100km thick
A mantle – has the properties of a solid but it can also flow
A core – made of molten nickel and iron. Outer part is liquid and inner part is solid
The average density of the Earth is much higher than the crust, so the inner core must be very dense
Movement of the Movement of the LithosphereLithosphereThe Earth’s LITHOSPHERE (i.e. the _______) is split up
into different sections called ________ plates:
These plates are moving apart from each other a few centimetres every _______ due to the ________ currents in the mantle caused by the ________ decay of rocks inside the core.
Words – radioactive, crust, convection, tectonic, year
Plate MovementsPlate Movements
Oceanic Crust
Mantle
Magma
Convection Currents
Earthquakes and volcanic eruptions can be common
here
The EarthThe Earth’’s Atmospheres Atmosphere
Carbon dioxide, water vapour
Oxygen Nitrogen Noble gases
For the last 200 million years the atmosphere has remained roughly the same – it contains 78% nitrogen, 21% oxygen, 1% noble gases and about 0.03% CO2
4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day
Evolution of the EarthEvolution of the Earth’’s s AtmosphereAtmosphere
Carbondioxide
Methane Ammonia Oxygen Nitrogen Others
Present day atmosphere contains 78% nitrogen, 21% oxygen, 1% noble gases and about 0.03% CO2
4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day
Evolution of the EarthEvolution of the Earth’’s s AtmosphereAtmosphere
Volcanic activity releases CO2, methane, ammonia and water vapour into the atmosphere. The water vapour condenses to form oceans.
Some of the oxygen is converted into ozone. The ozone layer blocks out harmful ultra-violet rays which allows for the development of new life.
Green plants evolve which take in CO2 and give out oxygen. Carbon from CO2 becomes locked up in sedimentary rocks as carbonates and fossil fuels. Methane and ammonia react with the oxygen and nitrogen is released.
One theory about how life was One theory about how life was formed…formed…The “Primordial Soup” theory:
A collection of simple molecules
like methane
Amino acids
Dr Stanley Miller 1930-
2007
In 1953 I conducted an experiment that proved that an electrical discharge can turn methane into amino acids! This is called the “Miller-Urey experiment”.
Carbon dioxide in the Carbon dioxide in the atmosphereatmosphereThe amount of CO2 in the atmosphere is affected by 3
things: 1) Geological activity moves carbonate rocks deep into the Earth and they release ______ _______ into the atmosphere during volcanic activity.
2) When fossil fuels are burned the carbon contained in them reacts with _____ to form CO2.
3) Increased CO2 in the atmosphere causes a reaction between it and _______. These reactions do not remove ALL of the new CO2 so the greenhouse effect is still getting _______!
Words – oxygen, seawater, carbon dioxide, worse
Separating airSeparating airAir can be separated into the different gases that make it up. To do this you first have to cool air down to -2000C and turn it into a liquid:
Liquid air
(-200OC)
Fractional distillation
In this chamber the air is gradually heated up again and the different parts of air “distil” off at different
temperatures according to their boiling points
Nitrogen
Argon
Oxygen
Remove CO2 and
H2O vapour
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