chemistry unit 1 - new syllabus revision notes GCSE

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  • Created by: xxSonia
  • Created on: 21-12-12 17:12
Chapter 1...
fundamental ideas
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atoms are neutral
do not have a charge
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protons are in the nucleus and
have a positive charge
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neutrons are in the nucleus and
have a no charge
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electrons orbit the nucleus and
have a negative charge
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mass number =
number of protons + number of neutrons in an atom
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atomic number =
number of protons
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number of protons in an atom =
number of electrons
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to workout the number of neutrons
minus the atomic number from the mass number
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electrons in an atom are arranged in ...
shells ( energy levels)
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in the 1st shell ...
a maximum of 2 electrons can fit
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in the 2nd shell ...
a maximum of 8 electrons can fit
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in the 3rd shell
a maximum of 8 shells can fit
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the periodic table
is arranged in groups
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atoms in group 1
have 1 electron in their outermost shell
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atoms in group 2
have 2 electrons in their outermost shell
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atoms in group 3
have 3 electrons in their outermost shell
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atom in group 0
have full outermost shell
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they are known as ...
the noble gases
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examples -
helium has 2 electrons in its outermost shell, neon has 8 electrons in its outermost shell e.t.c
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the noble gases
are totally nonreactive
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in other groups
the atoms in it have similar properties
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atoms in group 1 ...
are very reactive, soft and shiny when freshly cut. as you go down group 1 the elements gets less reactive
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atoms that are not the noble gases ( not in group 0) like to have
full outer most shells.
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they do this by
either gaining or losing an electron
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as a result they become
charged
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an atom which has a charge is called
a ion
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metal atoms ( sodium , magnesium , potassium) form
positive ions
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because they
lose 1 or more electrons
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non metal atoms ( fluorine , oxygen , nitrogen ) form
negative ions
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because they
gain 1 or more electrons
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as a result the oppositely charged ions will
attract each other ( similar to how magnets work )
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this called
ionic bonding
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however there is another form of bonding known as
covalent bonding
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this occurs ONLY with
non metals
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examples -
water , carbon dioxide ...
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here electrons are
SHARED
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as a result
non metal atoms have full outermost shells
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chapter 2 ...
rocks and building materials
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the scientific name for lime stone is
calcium carbonate
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it contains -
- calcium atoms - carbon atoms - oxygen atoms
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the formula is
CaCO3 ( there is actually a small 3 )
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limestone is used as a building material , it is used for many things such as
cement , concrete , tiles and glass
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when we heat limestone strongly
the calcium carbonate breaks down to form calcium oxide , carbon dioxide is also produced in this reaction
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breaking down a chemical while heating is called
thermal decomposition
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the word equation for heating limestone is
calcium carbonate ==> (heat) calcium oxide ( quick lime )+ carbon dioxide
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Calcium oxide +water =>
calcium hydroxide ( slaked lime )
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calcium hydroxide + carbon dioxide =>
calcium carbonate - in a solution + water
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calcium hydroxide ( slaked lime ) is used for
- neutralizing soils - neutralize acidic lakes - make lime mortar stick bricks together
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cement is made from
calcium oxide + clay + water
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we make cement in a
rotary klin
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disadvantages of cement
the making of it contributes at least 5% of carbon dioxide in the atmosphere which is a greenhouse gas- can crack along weak spots of the wall
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modern day mortar is made from
cement + water + sand
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lime mortar is made of
slatelime + sand + water
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advantages of lime mortar are
offers more flexibility and unlikely to arack
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disadvantages of lime mortar are
water prevents the lime from reacting with the carbon dioxide and does not harden quickly
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disadvantages of quarrying limestone are -
distruck habitats - visual pollution - dust pollution which can damage crops - quarrying produces alot of noise in quiet areas - limestone transpotation would create traffic and noise
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advantages of quarrying for limestone are -
- provides jobs for people - brings prosperity to whole community - provides country with valuable resources - the space provides houses and roads - limestone products is used to neutralize soils and acidic lakes - improve small business and economy
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carbonates react with acids to produce a
salt+ water + carbon dioxide
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examples include -
calcium carbonate + hydrochloric acid ==> calcium chloride + water + carbon dioxide
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concrete is made out of
small stones/ aggregate + water + cement + sand
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advantages of concrete
strong, cannot errode and cheap
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disadvantages of concrete
visually unattractive
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chapter 3
metal and their uses
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metals are found in the
earths crust
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a metal ore is
a rock which has enough metal or metal compound in a rock that makes it worth extracting the metal
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metals can be separated by
electrolysis or can be extracted using carbon
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however metals such as gold and silver are found
native ( pure) meaning they do not need to be extracted by electrolysis or carbon
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we extract a metal either by using electrolysis or by carbon according to
how reactive they are
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we know how reactive they are by using the
reactivity series
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the order of the reactivity series is
Potassium , Sodium , Calcium , Magnesium , Aluminium - these metals are only extracted by electrolysis
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continuing form the reactivity series
the following metals can only be extracted by using carbon ( except copper , silver and gold) Zinc , Iron , Lead , Copper , Silver , Gold
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metals under carbon in the reactivity series
can be extracted from their compound using carbon
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the extracting a metal using carbon is done by a metal oxide + carbon ==>
metal + Carbon dioxide
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examples include
lead oxide + carbon ==> lead + carbon dioxide
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the oxygen is removed from the metal . this is called a
Reduction Reaction
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we can extract iron from iron oxide by using
carbon and placing them in a blast furnace
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Iron oxide + carbon ==> (heat)
Iron + Carbon dioxide
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when we extract iron we get pure iron however it is
very soft and not very useful. Therefore we add more metals + elements to make it harder
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a metal that contains other elements is called an
alloy
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iron that has been alloyed with other elements is called
steel
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pure iron is soft but flexible ( malleable) the more impurities it has the
harder and more brittle it is
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carbon steels :
are the simplest steels - made up of iron and a little bit of carbon - this is the cheapest type of steel - used to make car bodies , knifes, machinery, ships and buildings
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stainless steel :
these are chromium steel - used to make cooking utensils, cutlery- very hard and strong - good at resisting corrosion ( don't rust)
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low carbon steel
soft , not easily shattered
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high carbon steel
very strong but brittel
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low alloy nickle steel :
resistant to stretching force
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low alloy tungsten steel:
works well in high temperatures
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high alloy chromium steel :
strong and chemically
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stainless steel :
hard , strong and corrosion resistant
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even though aluminum is reactive it does not corrode ( rust|)
this is because the surface atoms reacts with oxygen to forms a thin layer of aluminium oxide on the surface this forms a protective barrier which prevents rusting
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properties of aluminium are
- low density ( light) - excellent conductor of heat and electricity - can be shaped easily - quite strong - can be made stronger by alloying it with other metals
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the uses of aluminium include :
- drink cans - cooking foil - sauce pans
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aluminium can only be extracted by
electrolysis
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however there are disadvantages such as
- electrolysis is expensive - non environmentally friendly - uses up fossil fuels since it releases harmful / polluting gases
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the properties of titanium are
- silvery white metal - strong - resistant to corrosion ( has an oxide layer )like aluminium - low density - high melting point
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the uses of titanium include :
- make jets - high performance aircraft - racing bikes - nuclear reactors - used to make hip replacements since its strong and resists corrosion
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there are some disadvantages
- expensive to extract - bad for the environment
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why do we bother recycling metals like aluminium and titanium?
- better for the environment since it reduces the amount metals which involve using electricity and producing polluting gases - prevents us using limited resources
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other reasons why we bother recycling metals are :
- prevents accumulation of landfill sites - cheaper to recycle as we save extraction costs and cost of mining the metal
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one way of extracting copper is
melting the copper rich ore in a furnace , this is called smelting - the copper is then extracted by using electricity ( electrolysis)
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however the problems of this are
- its expensive - uses lot of energy - bad for the environment - copper rich ores are being depleted
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there are new ways of extracting copper these include
phytomining and bio-bleaching - these methods are used to extract copper from low grade ores
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phytomining is when you use plants to absorb metal compounds and the plants are then burned
then the metal can be extracted from the ash. The copper ions can be 'leached' (dissolved) by adding sulfuric acid . This makes copper sulphate. Then displacement is used with scrap iron and electrolysis is used to produce pure copper
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bio- bleaching when bacteria feeds on low grade ores.
then by a combination of biological and chemical processes we get a solution of copper ions. Once again we use scrap iron and electrolysis to produce pure copper
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the advantages of phytomining and bio - bleaching are
its greener , cheaper and you can get a decent amount of copper from low grade ores
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transitional metals are found in the central block of the
periodic table . like pure iron and copper it is too soft to be useful therefore we can make the copper harder by alloying it with tin to make bronze and zinc ti make brass
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transitional are very useful. examples include
copper can conduct water and electricity such for pipes and wires also to make coins
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some benefits of using metals in construction
lead can be bent easily so is used to seal joints , steel is strong for girders and scaffolding and aluminium alloys are corrosion resistant
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some drawbacks of using metals in construction
iron and steel can rust which can weaken structures e.f if iron rods are used to inside reinforced concrete it can rist and collapse structures - exploitation of metal ores to extract causes pollution and uses limited resources - more expensive
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chapter 4
crude oil and fuels
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crude oil is a mixture of
hydrocarbons. It is very valuable as we use it to make Petrol, Vaseline , Kerosine , Bitumen
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the hydrocarbons in crude oil are called
alkanes
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Alkanes have the general formula
CnH2n+2
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CH4 is
Methane ( natural gas)
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C2H6 is
Ethane
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C3H8 is
Propane
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we use fractional distillation is used to
separate the compounds in crude oil
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how does it work ?Firstly crude oil is heated to a very high temperature until it has been vapourised then the hot vapour passes into the fractionating (cooling)
tower. The different fractions that make up crude oil condense at different temperatures at different levels of the cooling tower. Short hydrocarbons condense at the top and the long hydrocarbons condense at a higher temperature at the bottom
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short hydrocarbon are
gases or thin liquids ( very runny - low viscosity) , Very flammable , Volatile ( tendency to turn into gas) and have a short boiling point
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long hydrocarbons are
thick ( high viscosity) , less flammable , not volatile and have a high boiling point
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a fuel is something that we
can burn and only do so with oxygen. when burnt it produces carbon dioxide and water vapour.As a result a fuel gives of heat energy
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complete combustion is when a
fuel + oxygen ===> Heat energy + Carbon dioxide + water vapour
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incomplete combustion is when a
fuel + limited oxygen ===> heat energy + carbon dioxide + water vapour + carbon monoxide
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particulates are solid particles containing
carbon and unburnt hydrocarbons. They can travel in the air and scientists think they damage cells in our lungs and can also cause cancer. They also create global dimming
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Catalytic Converters are devices that you fit into cars that break down
some of the polluting gases that are produces when the car engine burns the petrol fuel
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catalytic converts break down
carbon monoxide + nitrogen oxide ==> carbon dioxide + nitrogen
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the main disadvantage of catalytic converters is that
it produces carbon dioxide which is a greenhouse gas
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bio-fuels are a renewable e source of energy that
could be used to replace some fossil fuels e.g bio-diesel is made from oils extracted from plants
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another biofuel is ethanol
which we make by fermenting sugar from sugar beet /cane . This will save money as well our resource of crude oil.
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chapter 5
Product from oil
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Cracking is a process where by we heat the
hydrocarbon with a catalyst and the hydrocarbon will break down into 2 or more smaller hydrocarbons.
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A catalyst is substance that speed up
the rate of a chemical reaction
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Eg - C10H22 (Decane) =====> ( 800'C + catalyst)
C5H12 ( Pentane) + C3H6 ( Propene ) + C2H4 ( Ethene)
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alkANES have
the general formula CnH2n+2 , C ---- C ( single bonded ) and all bonds are single saturated
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alkENES have
the general formula CnH2n , C=C ( double bonded) and has unsaturated bonds
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To know we have a unsaturated hydrocarbon by doing a test which is known as the
Bromine test , where we react alkenes with bromine water to see if they are unsaturated
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Positive test = unsaturated hydrocarbon + bromine water ( orange - yellow ) ===>
products ( colorless)
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Negative test = saturated hydrocarbon + bromine water ( orange ) ===>
no reaction ( orange )
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Ploymer is a molecule made from
repeating units
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Monomer is a
small molecule
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Alkenes such as ethene cab become polymers this is done when the
alkene molecule join together , the double bond between the carbon atoms in each molecule 'open up'. it iis replaced by single bonds as thoussands of molecules join together. This reaction is called POLYMERISATION
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we can also write it more simply as : n C=C - many single ethene monomers ===>
( C---C ) n - long chain of polyethene ( where n is a large number )
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ethene ( C2H4) is the smallest unsatuated hydocabon molecule. We can tun into a polymer known as polyethene. Polyethene is a really useful plastic. It is
easy to shape, strong and transparent( unless we add coloring to it) plastic bags , plastic drink bottles, dustbins and clingfilm are all examples of polyethene
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Propene (C3H6) is another alkene. We can also make polymers with propene as a monomer. The polymer formed is called
polypropene. It forms a very strong, tough plastic. We can use it to make many things , including carpets, milk crates and ropes.
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new polymers are being developed all the time. They are designed to have
properties that make them specially suited for certain uses.
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Smart polymers may have their properties
changed by light, temperature or other changes in their surroundings
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we are now recycling more plastics and finding
new uses for them.
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non-biodegradable plastics cause
unsightly rubbish , can harm the environment as well as wild life and take up space in landfill sites.
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biodegradable plastics are decomposed by the action of
micro-organisms in soil. Making plastics with starch granules in their structure help the micro-organisms break down a plastic
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however there are disadvantages such as the
use of food crop like corn to make plastics instead can cause problems to developing countries who use the crop. In addition food prices would rise as the demand is more than the supply , as result it would be harder to survive .
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Another problem is
the destruction of tropical forests to create more farmland , will destroy the habitats wildlife and could cause global warming.
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although biodegradable plastics help conserve
the amount of crude oil we have. As well as get broken down much more quickly compared to non biodegradable plastics
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some plastics can be recycled. Once sorted into different types they can be
meltes down and made into new products. They can save energy and resources
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Ethanol is the alcohol found in alcoholic drinks. Ethanol for drinks is made by the
fermentation of sugar from plants
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Enzymes in yeast break down the sugar into ethanol and carbon dioxide gas :
sugar ( glucose) ===>(yeast) ethanol + carbon dioxide
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the formula equation is
C6H12O6 ===> 2C2H5OH + 2CO2
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Making ethanol from ethene is done by ethene gas can react with steam to make ethanol
the word equation is - ethene + steam ===> ( catalyst) ethanol
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the formula equation is
C2H4 + H20 ===> C2H5OH
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The reaction is called
HYDRATION
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Chapter 6
Plant oils
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There are two methods of extracting the oil from plans
pressing ( squashing the oil from plants) or distillation
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extracting lavender oil by distillation is done by :
1. plant is put into boiling water 2. Oil from the plant evapourates 3. Oil is collected by condensing it 4. Water and other impurities are removed
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Vegetable oil as food :
- Provides nutrients ( eg. olive oil contains vitamin E) - containd energy ( can be used as bio - diesel ) - Improve taste and texture - Some oils are unsaturated - more crisper outsidde and softer inside
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fats can be saturated or
unsaturated
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saturated fats - bad
- Bacon fat - Lard - Butter - Cream
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Unsaturated - good
- Vegetable oil - Olive oil - Sunflower oil - Seaseme seed oil
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Why is it better to eat more unsaturated fat than less saturated fat?
- Because due to the fact that saturated fat is deposited , in arteries it leads to it being clogged up and as a result you could have the risk of getting strokes and heart attacks
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un saturated vegetable oil is liquid at room temperature this can be inconvenient as it is not very useful. Therefore we
harden the vegetable oil and it turn into a solid at room temperature. This can be achieved by reacting the vegetable oil with hydrogen gas. To make the reaction to happen we use a nickle catalyst , and carry it out at 60'C
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Oils that we have treated like this are sometimes called
hydrogenated oils. They are solids at room temperature meaning we can make it into spreads like butter. We can also use them to make cakes , biscuits and pastry
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However when we when we do this the unsaturated oil becomes
saturated meaning it is unhealthy
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an emulsifier stops oil and water from
seperating out into layers and allows substances to be mixed
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an example of an emulsifier is
egg yolk
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ice cream , mayonnaise and salad cream are known as
emulsions because they contain emulsifiers
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an emulsifier works because the hydrophobic
tail of the molecule will dissolve in the oil,making tiny droplets. The hydrophilic head dissolves in the surrounding water .The heads are negatively charged . This means each droplet will repel other droplets therefore the tiny droplets disperse.
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emulsifiers improve the texture of foods
enabling water and oil to mix. This makes fatty foods more palatable and tempting to eat
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we call a substance that is added to food to
preserve it or to improve its taste , texture or appearance a food additive
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additives that have been approved for use in
Europe are given E numbers. These can be used to identify them.
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Chapter 7
Our changing planet
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the earth consists of a series of layers. Starting from the surface we have the
crust, the mantle then the core on the center. A thin layer of gases called the atmosphere surrounds the earth
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the earth's limited resources come from
its crust , the oceans and the atmosphre
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the earths' crust is cracked in several plates known as
tectonic plates
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tetonic plates on average move a few inches a year as a result they are
moving
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Deep within the earth , radioactive atoms decay producing vast amounts of energy.This heats up molten minerals in
the mantle which expand . They become less dense and rise towards the surface. Cooler material sinks to take their place.Forces created by these convection currents move the tetonic plates slowly over the surface of the earth. resuling in earthquakes
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earthquakes are hard to predict mainly because
we do not have a device which can sense them or tell when it is going to happen , we do not know what happens under the earths crust and earthquakes occur at random time periods meaning it is hard to predict them
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Alfred Wegner believed that all countries /contienets were once a massive contienent this is because he notices that
some continents had complementary shapes ( South America and Africa) as well as fossils show that the same reptiles and plants once lived ion both continents
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Wegners theory was known as continental drift however other scientist found in hard to except since
Wegner could not explain HOW the continents had moved
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his theory was finally shown right 50 years later when
scientists found that the sea floor is spreading apart in some places , where molten rock is spewing out between two continents. This led to the theory called plate tectonics
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in the 1st atmosphere ( 4.5 billion years ago) there was
- carbon dioxide - water vapour - ammonia and methane
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how did the atmosphere change?
firstly CO2 + water vapour + Ammonia + Methane had been released due to volcanoes erupting
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then water vapour condenses to form
oceans
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simple celled plant like organissms formed in the
seas. They photosynthesized converting CO2 ==>O2
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the oxygen meant that animals could
evolve
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then the ammonia reacted with the oxygen and formed
nitrogen and water
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aswell as the methane reacted with the oxygen and formed
carbon dioxide and water
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as a result present day
atmosphere is formed
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living organisms are made out of proteins. A protein is made up of a long chain of amino acids which contain
carbon,hydrogen,oxygen and nitrogen ( CHON)
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Miller and Urey tried to recreate the conditions that were apparent in the early atmosphere
to see if amino acids could be formed. If they could this could explain why life began
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They used a mixture of water, ammonia , methane and hydrogen to modal
the early atmosphere.
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Normally these gases wouldn't react however
they used a high voltage spark to provide the energy needed to cause the gases to react
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the spark represented
lightning storms which would have been apparent in the early atmosphere . The experiment ran for a week
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after a week , they analysed the mixture formed it looked like a brown
soup, In it they found 11 different amino acids
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this proved it was possible to make the molecules of life from gases that
may have been in our atmosphere. In other words biological materials could be made from non living material ( gases )
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however opponents argue that miller - urey experiment only worked in the absence of
oxygen.They believed oxygen would have been present. This would make any conclusions based on Miller - Urey or similar experimental results invalid
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other theories include
simple living organisms could have arrived in comets / meteorites. Their evolution started somewhere else as well as this it supports the theory of life in other planets
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another theory is that
in 1969 a meteorite fell from the sky above Australia and it contained amino acids
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Amino acide ==> proteins ==>
cells ==> living organisms
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what happened to all the CO2 in the 1st atmosphere ? - CO2 is very soluble + dissolves in our oceans
-plants photosynthesized - animal eat the plants so they contain carbon in them
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other reasons
-carbon is locked up carbonates as well as in fossil fuels
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the atmosphere today has
nitrogen - 78% , oxygen - 21% , carbon dioxide - 0.03 - 0.04% , argon - 0.9% and trace amounts of other gases
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carbon moves into and out of the atmosphere due
to plants, animals , the oceans and rocks
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the amount of carbon dioxide in the earths 's atmosphere has
risen in the recent past largely due to the amount of fossil fuels we now burn
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in the industry the gases are separated by
the fractional distillation of liquid air
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this is when liquids with different boiling points are
separated
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first we have to get air cold enough for it condense into a
liquid. It has to be cooled to a temperature of -200'C
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the carbon dioxide and water can be removed from the mixture
as they are solids at this temperature
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the different boiling points of the main substance left in the liquid air mixture are
Nitrogen : -196'C , Argon : - 186'C , Oxygen : - 183'C
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the liquid is then allowed to warm up at
-196'C nitrogen boils of first. It is collected at the top of the fractionating colum
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the air is then contiues to warm up until argon is removed and finally oxygen
is removed as a liquid at -185 , liquid oxygen is collected at the bottom of the fractionating column.
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liquid nitrogen is useful as it is used to store
sperm in hospitals to help in fertility treatment. Nitrogen gas is very nonreactive so we use it in sealed food packaging to stop food going off. nitrogen is used to make ammonia which we convert into fertilisers
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pure oxygen is used
to help people breathe often at an accident or at a hospital.
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THE END
PHEW :/ - hope u guys found this resource helpful !
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Comments

ellie

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this is amazing !

the real barack obama

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these are so helpful! thankyou so much

xxSonia

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glad they helped :)

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