Core Chemistry Revision Flash Cards Produced by Mr P Scutt
Core Chemistry Revision Flash Cards
Produced by Mr P Scutt
What is the difference between:- element
- compound- molecule- mixture
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1.1 Atoms, elements & compoundsThe Periodic table Contains about 100 different types of atomsfound naturally on Earth. The elements have been given chemical symbols that are Internationally recognised.
molecules:A group of atoms bonded together
compound:Two of more different atoms bonded together.
element:A substance that is made up of one kind of atom only.
mixture:Contains more than one substance, but they are not bonded together.
Na = sodium
Cl = chlorine
NaCl = sodium chloride
NaCl
O2 = oxygen molecule
Air contains:
O2 N2 CO2 water vapour, trace gases (e.g. Ar)
What are the sub-atomic particles and where are they found?
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How are electrons arranged in an atom?
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1.2 Atomic Structure
ProtonNeutron
Electron shell or orbital
Nucleus
Electron
A helium atom
Sub atomic particle Charge Mass
Proton +1 1
Neutron 0 1
Electron -1 0 (almost)
He4
2
Atomic mass (Ar)
Atomic number
Proton number
In an atom the number of protons equal the number of electronsAtoms: Have no charge
1.3 The arrangement of electrons in atoms
Electronic structure for K is: 2,8,8,1
First shell holds up to 2 electronsSecond shell holds up to 8 electrons
Third shell holds up to 8 electrons
Forth shell holds up to 18 electrons
nucleus
Energy levels increase as you move away from the nucleus
potassium
K
Electrons and the periodic table:Elements in the same group have the same number of electrons in its outermost shell, therefore the way they react is similar.
2,1lithium
2,8,1
sodium
2,8,8,1potassium
lithium + water lithium hydroxide + hydrogen
sodium + water sodium hydroxide + hydrogen
potassium + water potassium hydroxide + hydrogen
Balance the equation for:
H2 + O2 H2O
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How is calcium carbonate formed and what happens to it when it is
heated?
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1.5 Chemical equationsLaw of conservation of mass: States that the whatever mass is present on the reactants side will be present on the products side.
Balanced symbol equation: shows the same number of each type of atom on both
the reactant and product side
Step 1: Write a shopping list of atoms on both reactants and products side.
hydrogen + oxygen water
reactants products
H = 2
O = 2
H = 2
O = 1
H2 + O2 H2O
X
hydrogen + oxygen water
reactants products
H = 2 4
O = 2
H = 2 4
O = 1 2
2H2 + O2 2H2O
XX
X
hydrogen + oxygen water
reactants products
xH = 2
O = 2
H = 2 4
O = 1 2
X
X
Step 2: To balance the number of oxygen atoms on the product side we need to double the number of water molecules
H2 + O2 2H2O
Step 3: To balance the number of hydrogen atoms on the reactants side we need to
double the hydrogen molecules
2.1 Limestone and its uses
calcium carbonate calcium oxide + carbon dioxide CaCO3 CaO + CO2
Thermal decomposition (HEAT BREAKDOWN)
sediment layers built up over millions of years
dead shelled marine organisms
As sediment layers build up on top of the dead marine
organisms water is squeezed out ,it cements together and
limestone is formed
Formation of calcium carbonate
(limestone)
Rotary lime kilnHeats calcium carbonate strongly
to make calcium oxide. Energy costs are high & produces 5% of total CO2 caused by human activity. This contributes to global
warming and climate change.
What is produced when a metal carbonate is heated and how can
you test for the products?
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Draw the limestone reaction cycle
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2.2 Reactions of carbonates
All metal carbonates decompose, however the more reactive the metal carbonate is the more heat energy is required
Testing for CO2 Lime
water
metal carbonate
HEATcalcium hydroxide + carbon dioxide calcium carbonate + water
(limewater) (insoluble precipitate)
Ca(OH)2 + CO2 CaCO3 + H2O
LimewaterFrom: clear/colourlessTo: white precipitate
metal carbonate + acid salt + water + carbon dioxide
calcium + hydrochloric calcium + water + carbon carbonate acid chloride dioxide
CaCO3 + HCl CaCl2 + H2O + CO2
2.3 The “limestone reaction cycle”
1….
3….
4....
Thermal decomposition
Add waterAdd more
water & filter
Add carbon dioxide
2….
Calcium carbonate
Calcium oxide
Calcium hydroxide
Calcium hydroxide solution (limewater)
CaCO3 (s) CaO(s) + CO2(g)
CaO(s)+ H2O(l) Ca(OH)2(s)Ca(OH)2 (aq)
Ca(OH)2 (aq)+ CO2 (g) CaCO3 (s)+ H2O(l)
If you carry on blowing CO2 through, calcium hydrogen carbonate Ca(HCO3)2 forms; this does dissolve in limewater so
it changes back to clear and colourless
What is the difference between cement and concrete?
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Discuss the issues surrounding limestone quarrying.
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2.4 Cement and concrete
Problems with lime mortar:
Doesn’t set underwater (stops CO2 reacting) Too little sand = mortar shrinksToo much sand = brittle
Cement: Limestone is heated to form calcium oxide this is then mixed with powdered clay
Lime mortar: Calcium hydroxide mixed withsand & water. This then slowly reacts with CO2 in the air to form calcium carbonate (rock!)
calcium hydroxide + carbon dioxide calcium carbonate + water
Ca(OH)2 + CO2 CaCO3 + H2O
Concrete: Aggregates (crushed stones/gravel)are mixed with water, cement and sand.Resists crushing or squashing forces.Can be strengthened by adding steel rods(reinforced concrete) which resist pulling forces.
2.5 Limestone issuesLimestone Quarrying Usually blasted from the quarry using explosives.Dumped into large lorries to be processed.Much of it is processed nearby into cement.
Developments in concreteConcrete can be reinforced with: glass fibres, Kevlar, polypropene.Mixed with recycled paper = resists cracking, impact and cracking.Using reinforced concrete is cheaper than using steel although Steel is much more stronger (more resistant to snapping).
For quarrying• Local jobs (directly and indirectly)• local economy improves. • Limestone is supplied to industry (added to bread, cosmetics, paper).• Improve road links/by-pass.• Site can be re-beautified and used for leisure activities (lakes). = revenue/jobs after quarry closes.
Against quarrying• Many sites in National Parks.• Areas of habitat are destroyed.• Sites have unique/rare wildlife.• Blasting scares off wildlife (sheep!)• Increased traffic noise & jams.• Increased air pollution from lorries.• Increased risk of road accidents.• Dust lays on crops affecting yield.
Give an example of how electrolysis can be used to extract a
metal.
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Give an example of how carbon can be used to extract metal.
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3.1 Extracting metalsMost metals in the Earth’s crust are found as compounds, usually as an oxide or a carbonate. If a rock contains a high amount of a metal compound it becomes economical to extract. We call this rock an ore.
Haematite (Fe2O3) iron ore Bauxite (Al2O3) aluminium orePotassium
SodiumCalcium
MagnesiumAluminiumCARBON
ZincIronLead
CopperSilverGold
In
crea
sin
g r
eact
ivit
y
Carbon is more reactive than copper so it displaces it from its oxide
Reduction
Native Found naked, on its own!
Use electric to break down to separate the metal from the oxygen
Copper oxide + carbon copper + carbon dioxide CuO + C Cu + CO2
Electrolysis
Panning for gold!
reductionREDUCING AGENT
3.2 Iron and steelsTo remove iron from its ore(iron(III) oxide) we reduce
it in a blast furnace.
iron oxide + carbon iron + carbon dioxide 2Fe2O3 + 3C 4Fe + 3CO2
reductionREDUCING AGENT
Cast iron: 96% iron + impuritiesMakes it hard but brittle.
If we remove the impurities we get pure iron; although it is easily
shaped its too soft to use.
So we mix it with other elementsto form alloys of steel.
Pure iron: atom layers roll over each other making it easy to shape (malleable).
Elements such as carbon, nickel and chromium, disrupt the uniform pattern, so the atoms don’t roll over each other making it is harder to shape.
The higher the % of other element added the harder it is.
Examples:•Carbon steels•Low alloy steels•High alloy steels•Stainless steel
Does not rust, resists corrosionv. hard, strong
What are the main properties of aluminium and titanium? Why do
these properties mean that the metals have to extracted in
different ways.
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Discuss the steps to extract copper.
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3.3 Aluminium and titanium
Properties of aluminium:• High electrical & heat conductivity• Ductile (shape into wires)
Aluminium is ALLOYED to improve strength.Used to make: drinks cans, saucepans, cooking foil, aircraft & bike frames.
Aluminium at the surface reacts withoxygen, (in the air) forming a thin layer of aluminium oxide around it. This protects it from further corrosion.
Properties of titanium:• High melting point
Properties of both: >Silvery and shiny >Low density > Strong > Resistant to corrosion
layer of aluminium oxide
aluminium
Titanium is used to make: bike and air frames (low density & strength)Parts of jet engines (maintains its strength even at high temps)
Replacement hip joints (low density, strength and corrosion resistance)
Aluminium is extracted by ELECTROLYSIS. High energy costs to melt & electrolyse the Al ore.
Titanium is extracted by DISPLACEMENT using sodium (it’s more reactive) Na itself needs electrolysing from its ore + time consuming + energy costs
3.4 Extracting copper
Copper is purified using electrolysis
Copper rich ore e.g. chalcocite (Cu2S)
Waste SO2 gas is collected as it causes acid rain.
(environmental reason) It’s recovered to make sulfuric acid for extraction process (1)
(economic reason)
Two main extraction methods are used:1. React with sulfuric acid, to make copper sulfate solution.
Then iron is added to displace the copper from its sulfate.
2. Smelting (roasting): by heating the ore in air it is reduced.
copper sulfate + iron iron sulfate + copper
copper(I) sulfide + oxygen copper + sulfur dioxide
copper ore + sulfuric acid copper sulfate
Anode mud
TOXIC!
+ - XImpure copper Pure
copper
Cu2+ used for electrical
wiring
Discuss uses of different metals.
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Discuss the issues surrounding metals and their uses.
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3.5 Useful metals
CopperWater pipes (doesn’t react with water, can be bent)Wires (good electrical conductivity)Saucepans (good thermal conductivity, maintains shininess)
An alloy is (usually) a mixture of
metals. This makes the
metal harder.
Properties of transition metals: •Good conductors of heat & electricity•Strong•Bent or hammered into shapes
Transition metals
Copper alloys e.g. Bronze (copper + tin) Brass (copper + zinc) Brass harder than bronze used for making musical instruments.
Aluminium alloysMagnox = used in the building of nuclear power plants e.g. Sizewell A Duralumin = aircraft and bike frames (lightweight, strong)
Gold alloys Red gold (gold + copper) White gold (gold + nickel) Used in jewellery because it is hardwearing, shiny and colourful.
3.6 Metallic issuesOpen cast miningScar the landscapeCreate noise and dustDestroys habitatsLeave heaps of waste rock Phytomining
Plants absorb small quantities of metalions through their roots. Plants are then Burnt (possible production of electricity).If the metal is copper, sulfuric acid is added to make copper sulfate.
It is then reacted with iron in a displacement reaction.Finally electrolysis is used to get pure copper metal.
As rain water drains through exposed rock & slag heaps the groundwater becomes acidic. This then runs into rivers causing damage to the wildlife.
Recycling•Saves energy (& money)•Reduces the need to mine more ore•Conserves the Earth’s resources•Prevents pollution problems associated with extraction of metals from its ore ( see above)
BioleachingBacteria to feed on low concentration of metal ions. A chemical process then forms a leachate.
Iron in steel rusts weakeningit. Even protecting it with paint or grease costs money
What is meant by hydrocarbon and what are the properties of alkanes?
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Discuss the process of fractional distillation.
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4.1 Fuels from crude oil
Alkanes• Saturated hydrocarbons (contains maximum number of hydrogen atoms possible)• Contain single bonds• Has the general formula
Crude oilA mixture containing many different compoundsHydrocarbon
A compound containing hydrogen and carbon atoms ONLY.
SHORT CHAIN
e.g. methane
butane (C4H10)
H HC
H
H
H CC
H
H H
HH
methane (CH4)
ethane (C2H6)
Cn H2n+2
VOLATILITYTendency to turn
into a gas
BOILING POINT
VOLATILITY
VISCOSITY
FLAMMABILITY
LONG CHAIN
e.g. decane
(C10H22)
VISCOSITYHow easy it flows
FLAMMABILITYHow easy it burns
BOILING POINTTemp at which liquid boils
or gas condenses
4.2 Fractional distillationFractionsHydrocarbons with similar boiling points
kerosine
refinery gasesgasoline(petrol)
dieselresidue
Crude oil vaporised
residue
refinery gases
kerosine
diesel
gasoline(petrol)
bottled gas
SHORT CHAIN
LONG CHAIN
LOW BOILING POINT
HIGH BOILING POINT
Fractional distillation column
car fuel
aircraft fuel
lorry & car fuel
e.g. bitumenmaking roads
& flat roofs
Crude oil is fed in at thebottom as a hot vapour.The temperature in the column decreases as
you reach the top. Gases condense when they reach their boiling
point . So different fractions are collected
as liquids at thedifferent levels.
What happens when hydrocarbons are burnt?
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How can the burning of fuels be cleaner?
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4.3 Burning fuels (burning hydrocarbons)
Pollution from fuels.• Carbon monoxide is a poisonous gas (RBC pick up CO rather than O2). • Particulates (PM10’s) =Tiny solid particles of unburnt HC’s & carbon (soot) (damage cell lining of lungs & could cause cancer. Soot makes things dirty).• Many hydrocarbon fuels contain sulfur. This reacts with oxygen and when dissolved in water it forms acid rain. (damages forests, acidify lakes & land).• High temperature in the car engine allows nitrogen to react with oxygen to form nitrogen oxides (triggers asthma attacks and causes acid rain).
LimewaterClear/colourless
milky precipitate
Captures gases
FUELpropane
anhydrous cobalt
chloride paper
Blue pink
propane + oxygen water + carbon dioxide C3H8 5O2 4H2O + 3CO2
To pump to suck gases
through
water + carbon dioxide carbon monoxide + carbon
Incomplete combustion
(low O2 supply)propane + oxygen
Complete combustion
(good O2 supply)
ice
4.4 Cleaner fuelsCatalytic converter
carbon monoxide + nitrogen oxides nitrogen + carbon dioxide 2CO + 2NO N2 + 3CO2
Contains expensive precious metalsCatalysts works best at high temps
(so needs time to warm up).
clean gases + CO2
Flue gas desulfurisation
calciumhydroxide
Calcium sulfate
waste gases(sulfur dioxide)
Scrubs SO2 from waste gases then Clean gases arereleased into air.
Global dimming
USESplaster boardsplaster of Paris
Particulates in the upper atmosphere reflect back
sunlight. Rainfall patterns are affected & it even cools
the Earth (masking the effects of global warming).
Global warming
What are the alternatives to fossil fuels?
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How can the products of fractional distillation be made more useful?
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4.5 Alternative fuels1. They are carbon neutral.2. It burns with a much cleaner flame (compared to fossil fuels).3. It comes from a renewable resource (crops).4. If it is spilled it breaks down faster than normal diesel.5. It produces little sulphur dioxide gas and other pollutants .
hydrogen + oxygen water 2H2 + O2 2H2O
Hydrogen as a fuel:Burns with a clean flame.No pollution so no env- effects
Problems: SAFETY: Hydrogen/oxygen mix is explosive when ignited. Possibility
of gas leaking, or accidents.
STORAGE: Hydrogen as a gas takes up more space than a liquid
Bio
fuels/ B
iod
iesel
Crops are grown to make biofuels requires land = habitat loss Biofuels generate money for the economy, however their will be less food crops = price increases = risk of famine.
How can the products of fractional distillation be made more useful?
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Some of the products are long-chained and therefore not very useful. They can be broken into smaller chains using the process of “cracking”.
This is carried out by heating the hydrocarbon to form a vapour. Passing it over a powdered catalyst. (Aluminium oxide)
At 400C
What is the structure of the first two alkenes?
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What is the structure of the first four alkanes?
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What is the structure of the first four alkenes?
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Remember:Alkenes have 1 double bond between two carbon atoms.
What is the structure of the first four alkenes?
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Remember:
MEPB
M – 1 carbonE – 2 carbonsP – 3 carbonsB – 4 carbons
How can you test to see if a material is a alkane or alkene?
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How can ethanol be produced?
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How can you test to see if a material is a alkane or alkene?
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You test for the presence of a double bond in the alkene
By adding to bromine water (orange)This will decolourise the water
How can ethanol be produced?
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Ethene + SteamProduces ethanolAs it is hydrated
Ferment sugar using yeastSugar carbon dioxide + ethanol
This happens at a low temperature and so is cheaperSugar is renewable and more can be grown
Although product is not as pure
How are polymers formed?
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Where are polymers used?
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How are polymers formed?
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Alkenes can under go a process called polymerisationThis is where small molecules join up to produce long chains of repeating units, called monomers.
Example:Ethene produces polyethene.
Propene produces polypropene.
Depending on the conditions (temperature and pressure) they were made in, their properties differ. They are cheaper than metals, however crude oil is being used up.
Where are polymers used?
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Bags – polyethene – as light and stretchy
Lyrca – elastic properties
Waterproof coatingsDental fillings
Medicine – wound dressings (hydrogel)Biodegradable packaging – cornstarch added to material
Memory foam – beds, pillows,
Where do plant oils come from and how are they used?
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Compare saturated and unsaturated fats/oils?
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Where do plant oils come from and how are they used?
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Fruits and seeds contain oilThese can be extracted and used as fuel
By crushing the seed/fruit in a pressUsing a centrifuge – which is like a large tumble drier and separates the oil from the other solid bits.
Distillation refines the oil by removing water.
Used in foods (high energy content), cooking (high temperatures and flavour), fuels (biodiesel)
Compare saturated and unsaturated fats/oils?
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Saturated – no double bondsUnsaturated – contains double bonds
Unsaturated oils can be hydrogenated – where extra hydrogen can be added to it. Process uses Nickel catalyst
At 60CThe product is a solid, high melting points, used from spreads
Margarine is partially hydrogenated – partly solid but still can flow and spread easily.
Saturated fats are bad for you as they increase your cholesterol in your blood.
What is an emulsion and how is it useful?
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What is Wegner’s Theory?
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What is an emulsion and how is it useful?
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Oils don’t dissolve in waterIf you mix with water they make an emulsion (droplets suspended in water)
Emulsions are thicker than oil and water
Examples: Mayonnaise, Ice-Cream,
What is Wegner’s Theory?
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He realised that there were similar fossils found on opposite sides of the Atlantic ocean – he asked how.
He proposed that idea that once all the land on Earth was as one – a huge super continent called Pangea. Overtime, the land has been pulled apart.
This is by tectonic plates moving. This can be seen now by the different land masses fitting together like a jigsaw – matching shape, rock types and fossils.
What is the Earth’s structure?
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Discuss the role of tectonic plates.
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What is the Earth’s structure?
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Inner core – solid – under huge pressure from the rock above to cause it to be solid as all the particles are forced together. Iron and Nickel found here to give magnetic properties.
Outer core – Liquid (very hot area where the heat is from the radioactive decay of elements)
Mantle – semi-liquid (where convection current occur to move tectonic plates).
Crust – solid
Discuss the role of tectonic plates.
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The crust of the Earth is split into different plates called tectonic plates.
These sit on top of the mantle. As the mantle is semi-liquid, convection currents cause the tectonic plates to move.
At the edge of the plates, where they meet (plate boundary), volcanoes and earthquakes occur. These though can not be predicted as they are random events.
What are the main stages in the evolution of the atmosphere on Earth?
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What are the main stages in the evolution of the atmosphere on Earth?
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1. Volcanic Earth – very hot, lots of Carbon Dioxide in the air. No water as too hot. 2. Earth cools and oceans begin to form, trapping some carbon dioxide in the water.
3. Plants and algae grow and begin to pollute the atmosphere with oxygen and remove carbon dioxide, by the process of photosynthesis.
4. Carbon is trapped in the formation of sedimentary rocks. 5. Oxygen forms the Ozone layer, a layer in the atmosphere that protects us from harmful rays. 6. Todays atmosphere is mainly Nitrogen 78% and Oxygen, which allows us to live on the Earth.