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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