14/05/23

Chemistry 1Chemistry 1

14/05/23The structure of the atomThe structure of the atom

Electrons in shells

Proton in nucleus

Neutron in nucleus

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)

14/05/23Symbols Symbols Elements are represented by symbols

Elements, compounds & Elements, compounds & mixturesmixtures

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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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Mendeleev

Periodic tablePeriodic table

He

Reactive metalsTransition metals

Other metals

Non-metalsNoble gases

Separates metals and non-metals

Columns called groups

Rows called periods

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

14/05/23CompoundsCompoundsCompounds are formed when two or more elements are chemically combined. Some examples:

Glucose

MethaneSodium

chloride (salt)

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

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

-

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

LimestoneLimestonePositives of quarrying•Provides jobs•Provides materials•Provides neutralisation products

Negatives of quarrying•Destroys habitats•Produces noise and dust•Transportations makes pollution•Destroys landscape

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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

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

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

+ + + +

----

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

+

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.

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

14/05/23Properties of metalsProperties of metals• Strong• Can be bent• Can be hammered • Good conductors of heat and electricity

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

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

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

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

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

14/05/23PatternsPatterns

Longer chains mean…

1. More viscous

(gloopy)

2. Less flammable

3. Higher boiling pointIncreasing length

14/05/23FuelsFuelsA fuel is burned to release energy

Coal, oil and gas are fossil fuels.

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

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

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.

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

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

Testing for alkenesTesting for alkenes 14/05/23

Unsaturated alkene

Colourless bromine water

Orange bromine water

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

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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)

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

Extracting plant oils

• Extracted from fruits and seeds• Plant material is crushed, pressed and filtered

to remove impurities

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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

Emulsifiers - HT 14/05/23

Emulsifiers have a

water

oil

emulsifierhydrophilic (likes water,

hates oil) part

hydrophobic (likes oil, hates water) part.

Saturated and unsaturated oils

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Vegetable oils are unsaturated. They have a carbon-carbon double bond.Tested for bromine water

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

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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

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.

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.

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

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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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.