09/03/2016 chemistry 1. 09/03/2016 the structure of the atom electrons in shells proton in nucleus...
DESCRIPTION
09/03/2016 Mass and atomic number ParticleRelative MassRelative Charge Proton1+1 Neutron10 ElectronAlmost 0 MASS NUMBER = number of protons + number of neutrons SYMBOL PROTON (ATOMIC) NUMBER = number of protons (or electrons)TRANSCRIPT
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14/05/23
Chemistry 1Chemistry 1
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14/05/23The structure of the atomThe structure of the atom
Electrons in shells
Proton in nucleus
Neutron in nucleus
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14/05/23Mass and atomic numberMass and atomic numberParticle Relative Mass Relative ChargeProton 1 +1
Neutron 1 0Electron Almost 0 -1
MASS NUMBER = number of protons + number of neutrons
SYMBOL
PROTON (ATOMIC) NUMBER = number of protons (or
electrons)
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14/05/23Symbols Symbols Elements are represented by symbols
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Elements, compounds & Elements, compounds & mixturesmixtures
14/05/23
Elements – contain one type of atoms
Mixtures – two or more elements not chemically joined
Compounds – two or more elements chemically joined
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14/05/23
Mendeleev
Periodic tablePeriodic table
He
Reactive metalsTransition metals
Other metals
Non-metalsNoble gases
Separates metals and non-metals
Columns called groups
Rows called periods
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14/05/23Electron structureElectron structure
Potassium has 19 electrons. These electrons occupy specific energy levels “shells”…
Nucleus
The inner shell has 2 electronsThe next shell has 8 electronsThe next shell has 8 electronsThe next shell has the remaining 1 electronElectron configuration = 2.8.8.1
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14/05/23CompoundsCompoundsCompounds are formed when two or more elements are chemically combined. Some examples:
Glucose
MethaneSodium
chloride (salt)
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14/05/23Covalent bondingCovalent bonding
Hydrogen has just 1 electron in its outer shell. A full (inner) shell would have 2 electrons, so two hydrogen atoms get together and “share ” their electrons:
Now they both have a full outer shell and are more stable. The formula for this molecule is H2.
Atoms sharing electrons is called covalent BONDING. This bonding occurs between non-metals atoms. Each atom make enough covalent bonds to fill it’s outer shell
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14/05/23Ionic bondingIonic bonding
Na
Na
+
This is where a metal bonds with a non-metal. Electrons are transferred between atoms. Metal atoms lose electrons to form positive ionsNon-metals gain electrons to form negative ions
Sodium in Group 1 has 1 electron on its outer shellChlorine in Group 7 has 7 electrons in outer shell. Sodium transfers 1 electron – so both atoms have a full outer shell and are stable. Positive and negative charges attract
A positively charged sodium ion
A negatively charged chloride ion
Cl
Cl
-
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14/05/23LimestoneLimestoneLimestone is a sedimentary rock made up of mainly calcium carbonate. It’s cheap and easy to obtain by quarrying.
UsesBuilding materialsMaking cement. CaCO3 heated with clayMaking mortar. Cement mixed with sand and water Making concrete. Cement mixed with sand and aggregateNeutralising acidic soil & lakes - slaked lime
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LimestoneLimestonePositives of quarrying•Provides jobs•Provides materials•Provides neutralisation products
Negatives of quarrying•Destroys habitats•Produces noise and dust•Transportations makes pollution•Destroys landscape
14/05/23
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14/05/23The “Limestone Cycle”The “Limestone Cycle”Calcium Carbonate
(CaCO3)
calcium oxide + carbon dioxide CaO (quicklime) + CO2
calcium hydroxideCa(OH)2 (slaked lime)
Step 1: CaCO3 heated – thermal
decomposition
Step 2: add water to
quicklime
Step 3: add carbon
dioxide to slaked lime
+ water
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Metal extraction Metal extraction 14/05/23
Metals can either be found native in the ground (e.g. gold) or are found as metal ores (e.g. iron = haematite, aluminium = bauxite)
Metals above carbon extracted by electrolysisbelow carbon extracted by reductionsilver and gold found native
incr
easi
ng r
eact
ivit
y
potassiumsodiumcalcium
magnesium
aluminiumcarbon
zincironlead
coppersilvergold
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Reduction Reduction 14/05/23
Reduction is the removal of oxygen
The metal ore is reacted with carbon. The carbon is more reactive so removes the oxygen from the ore
iron oxide + carbon carbon dioxide + iron
carbonzincironlead
copper
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+ + + +
----
ElectrolysisElectrolysis 14/05/23
Electrolysis is breaking down a substance usingelectricityIt needs a liquid to conduct electricity. High temperatures are needed, which needs a lot of energy making it expensive
potassiumsodiumcalcium
magnesiumaluminium
carbon
Solution containing copper ions
Negative electrode made of pure copper
– gains Cu2+
ions = grows
Positive electrode made
of impure copper – loses
Cu2+ ions = shrinks
Cu2
+
Cu2
+
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Bioleaching & phytominingBioleaching & phytomining14/05/23
New mining techniques used to extract copper and decrease the effects of metal extraction on the environment. Bioleaching uses bacteria to separate copper from copper sulphide. The solution produced (leachate) contains copper which can be filtered.
Phytomining uses plants grown in soil containing copper, which builds up in leaves. Leaves burnt and copper in ash can be collected.
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Recycling metals Recycling metals
Fossil fuels running out Recycling uses less energy than
mining Recycling saves money Recycling cuts down on landfill sites Recycling reduces amount of pollution
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14/05/23Properties of metalsProperties of metals• Strong• Can be bent• Can be hammered • Good conductors of heat and electricity
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14/05/23Copper, Aluminium and Copper, Aluminium and TitaniumTitanium
Metal Properties Uses
Copper
Good electrical conductor, hard,
strong, can be bent, doesn’t
react with water
Electrical wires, plumbing pipes
and tanks
AluminiumCorrosion
resistant, low density, forms
hard alloysAeroplanes
TitaniumLow density, very
strong, corrosion resistant
Hip replacements
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14/05/23AlloysAlloysAn “alloy” is a mixture of metals.Alloys are harder than pure metals
Gold mixed with copper
Aluminium mixed with magnesium and copper
Aluminiun mixed with chromium
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14/05/23Using IronUsing Iron Iron produced by the blast furnace contains about 96% iron and 4% impurities. These impurities make it very brittle and easy to break. Iron is alloyed to make steel.
Steel with a low carbon content is easily shaped
Steel with a high carbon content is strong but brittle
Steel with chromium and nickel is called stainless steel
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Crude oil Crude oil 14/05/23
Crude oil is a mixture of hydrocarbons (only contains elements hydrogen and carbon)
The separate parts – fractions – can be extracted by fractionating distillation
Crude oil piped in at bottom of fractionating column, heated, oil evaporates and rises. Fractions condense and are collected
Decreasing temperature
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14/05/23AlkanesAlkanesAlkanes are saturated hydrocarbons - all of the atoms are held together by single bonds.General formula is CnH2n+2 - twice as many hydrogen atoms as carbon atoms plus an extra two
Methane – CH4
Ethane – C2H6
Propane – C3H8
Butane – C4H10
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14/05/23PatternsPatterns
Longer chains mean…
1. More viscous
(gloopy)
2. Less flammable
3. Higher boiling pointIncreasing length
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14/05/23FuelsFuelsA fuel is burned to release energy
Coal, oil and gas are fossil fuels.
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14/05/23Burning Fossil FuelsBurning Fossil FuelsBurning fossil fuels (combustion) releases gases and particles
CH
H
H
HOO
OO
OH HOH H
CO
O
Complete combustion (plenty of oxygen) produces carbon dioxide and water
Carbon dioxide is a “greenhouse gas” – cause global warmingIncomplete combustion (not enough of oxygen) produces carbon monoxide and carbon
OOCH
H
H
H CO
Carbon monoxide is a poisonous gas
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Sulphur dioxideSulphur dioxide 14/05/23
Burning coal releases sulphur dioxide and nitrogen oxides Sulphur dioxide and nitrogen oxides cause acid rain and “global dimming” – sunlight is absorbed by the particles in the atmosphere.Acid rain kills trees, causes lakes to become acidic killing wildlife and damage limestone buildigns and statues
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Alternative fuels Alternative fuels 14/05/23
Fuel Pros ConsEthanol – made from plant material
Carbon neutral – CO2 used for plant to grow. Other waste product is water
Engines need to be converted. Isn’t widely available yet.
Biodiesel – made from vegetable oils
Carbon neutral. Engines don’t need to be converted. Produces less SO2
Expensive to make, would increase food prices
Hydrogen gas – made from water
Very clean – no pollution
Need special, expensive engines. Isn’t widely available. Need to use energy to make it.
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14/05/23CrackingCrackingUseful short chain hydrocarbons can be made from long chain hydrocarbons by “cracking”:
Long chain hydrocarbo
nHeated catalyst
Liquid hydrocarbon
Gaseous hydrocarbon
Long chain hydrocarbon heated to thermally decompose.Hydrocarbon vaporises, passes over a catalyst and splits into an alkane and an alkene
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14/05/23AlkenesAlkenesAlkenes are unsaturated hydrocarbons – there is a double bond between 2 carbon atoms. General formula is CnH2n - twice as many hydrogen atoms as carbon atoms
Ethene – C2H4
Propene – C3H6
Butene – C4H8
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Testing for alkenesTesting for alkenes 14/05/23
Unsaturated alkene
Colourless bromine water
Orange bromine water
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Making ethanol
1) Ethene reacted with steam in presence of catalyst. Ethene comes from crude oil – will eventually run out
2) Sugar fermented with yeast. Carbon dioxide also produced. Sugar grown - renewable
14/05/23
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14/05/23Monomers and PolymersAlkenes can be used to make polymers (plastics) Lots of small alkene molecules – monomers – are joined together to make very large molecules – polymersEthene poly(ethene)Propene poly(propene)
C Cn C Cn
Ethene Poly(ethene)
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14/05/23Properties & uses of polymers
• Light and stretchy – used for plastic bags
• Elastic – used to make Lycra• Waterproof – fabric coating• Non-biodegradable – don’t rot
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Extracting plant oils
• Extracted from fruits and seeds• Plant material is crushed, pressed and filtered
to remove impurities
14/05/23
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Emulsions 14/05/23
Emulsions are a mixture of oil and water. Droplets of one liquid are suspended in the other liquid.Emulsions are thicker and have lots of uses – mayonnaise, ice cream and paint are examples
Emulsifiers stop emulsions fromseparating – e.g. egg yolk
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Emulsifiers - HT 14/05/23
Emulsifiers have a
water
oil
emulsifierhydrophilic (likes water,
hates oil) part
hydrophobic (likes oil, hates water) part.
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Saturated and unsaturated oils
14/05/23
Vegetable oils are unsaturated. They have a carbon-carbon double bond.Tested for bromine water
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Hydrogenating oil- HTUnsaturated vegetable oil can be hardened by reacting them with hydrogen in the presence of a nickel catalyst at 60oC.
Hydrogen adds to the carbon-carbon double bond.
Hydrogenated oils have higher melting points = solid at room temperature. Useful for cakes and pastries
14/05/23
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14/05/23The Structure of the EarthThin crust - 10-100km thick
Mantle – has properties of a solid but it can also flow
Core – made of molten nickel and iron. Outer part is liquid and inner part is solid
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14/05/23Tectonic platesThe Earth’s crust is split up into tectonic plates:
These plates are moving apart from each other a few centimetres every year due to convection currents in the mantle caused by the radioactive decay of rocks inside the core.
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14/05/23Tectonic theoryIt was once thought that the oceans and the continents were formed by shrinkage from when the Earth cooled down after being formed.
Alfred Wegener proposed that there was once a single land mass, that has changed as tectonic plates moved - TECTONIC THEORY. The evidence he had wasthe continents look like they “fit” together. had similar rock patterns and fossil records.
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14/05/23
The Answer:1) Scientists discovered 50 years later that the Earth
generates massive amounts of heat through radioactive decay in the core. This heat generated convection currents in the mantle causing the crust to move
2) We also now know that the sea floor is spreading outwards from plate boundaries
Tectonic theory
Wegener couldn't explain how continental drift happened so
nobody believed him
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14/05/23Movement at boundariesMovement of plate boundaries can be sudden and
disastrous.
Earthquakes and volcanoes happen at the boundaries between
tectonic plates
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14/05/23
4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day
Evolution of the Earth’s AtmosphereCarbon
dioxideMethane Ammonia Oxygen Nitrogen Others
Present day atmosphere = 78% N, 21% O2, 1% noble gases and about 0.03% CO2
Phase 1 – volcanoes give out CO2, H2O, CH4 & NH4. Water vapour and carbon dioxide condensed to form oceans
Phase 2 – green plants evolved, using up CO2 and producing O2.