C1b

-Fractions from fractional distillation aren't very useful because they are long chain hydrocarbons

-Fractions from crude oil are heated strongly to turn the hydrocarbons into gas

-This is then passed over a hot catalyst where thermal decompostion takes place, large hydrocarbon molecules are spilt into smaller, more useful ones 

-Cracking forms an alkane and alkene 

-Alkene->unsaturated, alkane->saturanted 

-To test is a hydrocarbon is saturated or not you can use bromine water, if a unsaturated hydrocarbon is present it will turn the bromine water from orange/brown to colourless,if a saturated hydrocarbon is present, the bromine water won't change colour 

-Plastics are made up of huge molecules from lots of small molecules that have joined together, the small molecules are called momomers 

-Lots of momomors joined together forms a polymer 

-Ethene is the smallest unsaturated hydrocarbon, we can turn it into a polymer known as polyethene

-Polyethene is a useful plastic, it is; easy to shape, strong and transparemt

-Examples of polyethene;plastic bags, plastic drinks bottles and clingfilm 

-Another alkene is propene which can be turned into the plastic ploypropene, which is strong, tough plastic, used to make crates and rope 

-When alkene molecules join together, the double bond between the carbon atoms in each molecule breaks,it is replaced by single bonds as thousands of molecules join together (this is an addition reaction/addition polymerisation)

Forces between molecules are called intermolecular forces, the size of this force between polymer molecules depends on;

• the monomer used 
• the conditions we choose to carry out polymersation 

-Thermosoftening plastics- plastics with weak intermolecular forces, when heated the intermolecular forces break making the plastic soft, when it cools the intermolecular forces bring the polymer molecules back together and the plastic hardens again 

-Polyethene and polypropene are examples of thermosoftening plastics

-Two types of polyethene;

• HDPE (high density)- using a catalyst at 50 degrees and a slightly raised pressure, made up of straight polyethene molecules, can pack closely together, stong intermolecular forces
• LDPE (low density)-high pressures and a trace of oxygen, polymer chains are branched and they can't pack closely together 

-Thermosetting plastics, where momomers make chemical bonds between the polymer chains when they are heated in order to shape them, these bonds are strong,and stop the plastic from softening when we heat it in the future

-Farmers plant crops like oilseed ****, once it has flowered and set seed,the farmer collects the seeds using a combine harvester 

-The seeds are then taken to a factory where they are crushed, then pressed to extract the oil in them 

-The impurities are removed from the oil

-We extract other vegetable oils using steam,e.g lavender oil is extracted from lavender plants by distillation 

-Plants are put into boiling water and the oil from the plant evapourates, and collected by condensing it

-All vegetable oils have molecules which contain chains of carbon atoms with hydrogen atoms attatched to it 

-Unsaturated oils contain and double bond between two carbon atoms 

-Farmers plant crops like oilseed ****, once it has flowered and set seed,the farmer collects the seeds using a combine harvester 

-The seeds are then taken to a factory where they are crushed, then pressed to extract the oil in them 

-The impurities are removed from the oil

-We extract other vegetable oils using steam,e.g lavender oil is extracted from lavender plants by distillation 

-Plants are put into boiling water and the oil from the plant evapourates, and collected by condensing it

-All vegetable oils have molecules which contain chains of carbon atoms with hydrogen atoms attatched to it 

-Unsaturated oils contain and double bond between two carbon atoms 

-The temperature that a liquid boils at depends on the size of the forces between its molecules,the bigger the forces,the higher the liwuid's boiling point 

-The molecules in vegtable oils are much bigger than water molecules,making the forces between the molecules in vegetable oils much larger

-When we cook food in vegetable oil the result is very different to when we cook it in water because vegetable oils can be used at a much higher temperature 

-Cooking foods in oil also means that the food absorbs some of the oil, vegetable oil contains a lot of energy

-Unsaturated vegetable oils are usually liquids at room temperature, because the double bond between the two carbon atoms stop the molecules fitting together well 

-The boiling and melting points of the oils can be increased by adding hydrogen to the molecules, the reaction replaces the double carbon-carbon bonds with single carbon-carbon bonds, allowing the molecules to fit nex to each other better

-This turns the oils to a soild,this process is known as hardening 

-Emulsion-> A mixture of tiny droplets of one liquid in another liquid 

-Emulsifier-> A substance which stops the two liquids in an emulsion seperating

-e.g egg yolk is an emulsifier for the water and oil in mayonnaise 

-An emulsifier has a head and a tail, the head is attracted to water (hydrophillic) and the tail is attracted to the oil (hydrophobic)

-Food additive-> substance added to food to make it keep longer, improve its taste or appearance

-E numbers are used to identify these;

• E1- colours, improve apperance
• E2- preservaties, help food keep longer
• E3- antioxidants,help to stop food reacting with oxygen 
• E4- emulsifiers,stabilisers and thickeners, help improve the texture of food
• E5-acidity regulators, helps control the pH
• E6-flavouring

-Biodiesel-> fuel mae from vegetable oils 

-Most modern biodisel is made by treating vegetable oils to remove some unwanted chemicals 

-Advantages of using biodiesel;

• clean fuel
• if it's spilt it breaks down 5x faster than 'normal' diesel 
• burns more clearly 
• makes little sulfur dioxide and other pollutants
• the crops used to make biodiesel absorb carbon dioxide gas as they grow, biodiesel is carbon-neutral (the amount of carbon dioxide given off is nearly balanced by the amount absorbed 

-Another biofuel is ethanol, made by fermentation of sugar from sugar beet or sugar cane 

-The ethanol gives off carbon dioxide when burnt,sugar cane absorbs it during photosynthesis 

-Ethanol can also be made from the ethene we get by cracking the heavier fractions of crude oil 

-The Earth is made up of 4 layers; inner core, outer core, mantle and crust 

-The crust is very thin (5km-70km)

-The mantle is nearly 3000km, it behaves like a solid,but can flow in parts very slowly

-The core is made of a mixture of iron and nickel, the outer core is liquid and the inner core is solid 

-Scientists thought that features like mountain ranes on the surface of the Earth were caused by the crust shrinking as the early molten Earth cooled down 

-The original supercontinent was known as Pangaea

-Over the years the techtonic plates on the Earth's crust have moved away from each other 

-In the mantle radioactive decay produces heat which creates convection currents in the mantle which is what causes the techtonic plates to move 

-Evidence for continents such as Africa and South America once being next to each other are;

• similar fossils found in each area 
• similar rock type found in each area 
• fit together like a jigsaw puzzle 

-Where the plate boundaries meet, huge forces are exerted. These can cause earthquakes if they have a sudden movement between them 

-If earthquakes happen under sea they can cause tsunamis 

-He thought that a huge southern continent had sunk

-He suggested that this has left beind land bridges between Africa and South America, which animals could cross

-The idea of continenta drift was first put forward by Alfred Wegener in 1915

-However, no one accepted his ideas, could explain how, no evidence 

-Scientists think the earth was formed about 4.5 million years ago 

-To begin with it was a molten ball of rock and minerals 

-The Earth's surface was covered with volcanoes belching fire and smoke into the atmosphere 

-The volcanoes released carbon dioxide,water vapour and nitrogen gas, which formed the Earth's early atmosphere 

-Water vapour in the atmosphere condensed as the Earth gradually cooled, and fell as rain creating the first oceans 

-The Earth's early atmosphere was mainly carbon dioxide, some water vapour, nitrogen and traces of methane and ammonia, with no or little oxygen 

-Carbon dioxide was removed by trees and plants using it for photosynthesis giving us oxygen 

-Carbon dioxide levels have decreased due to plants taking it in for photosynthesis and is 'locked up' in sedimentary rocks, and dissolved into the oceans 

-Ammonia and methane reacted with the oxygen in the air which got rid of them but increases carbon dioxide and nitrogen levels;

CH4 +2O2->CO2 +2H2O

4NH3+ 3O2->2N2 +6H20 

-Nirtogen-> 78%

-Oxygen->21%

-Argon->0.9%

-Carbon dioxide->0.04%

-The Earth's atmosphere contains tiny amounts of noble gases

-They are unreactive, and exist as single atoms

-Because they are unreactive we use them in situations where they are useful due to their lack of reactivity;

-Helium-> used in airships and party balloons, low denisty so it floats, safe because it doesn't catch fire

-Neaon-> neon lights, when an electrical current is passed through neon gas it gives out a bright light

-Argon-> used for the filament inside a light bulb, because it doesn't react 

(PICTURE OF CARBON CYCLE)

-More fossil fuels being burnt has increased the levels of carbon dioxide 

-When we burn fossil fuels, carbon which has been locked up for hundereds of years in the bodies of living animals, is released as carbon dioxide into the atmosphere e.g;

propane + oxygen -> carbon dixoide + water 

-As carbon dioxide levels in the atmosphere go up, the reaction between carbon dioxide and sea water increases 

-This reaction makes insoluble carbonates (mainly calcium carbonate), which are deposited as sediment on the bottom of the ocean 

-It also produces soluble hydrocarbonates, mainly calcium and magnesium, which remain dissolved in the sea water 

-In this way seas and oceans act as a buffer,absorbing excess carbon dioxide but releasing it if necessary, however this buffing system probably cannot cope with the additional carbon dioxide being produced