Chemistry Study Notes Igcse Edexcel

8/17/2019 Chemistry Study Notes Igcse Edexcel

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CHEMISTRY STUDY NOTES IGCSE EDEXCEL;

SECTION A: Particles

Particlearrangement

Movement Forces of attraction

Solid Closely, regularlypacked

Vibration in a xedposition

Strong

Li uid !ouc"ing #it"some gaps

Can be pus"edaside and slideover eac" ot"er

$ot as strong ore%ective

&as Furt"er apart Move randomly inall directions

'xtremely #eakconsidered as non(existent

)"en a solid is "eated, t"e particles vibrate faster and faster until t"ey are fastenoug" t"at t"e forces of attraction are no longer able to "old t"em in a solid* !"esolid t"en melts into a li uid* )"en it is cooled, t"e li uid particles #ill move aroundmuc" slo#er enoug" t"at t"e forces of attraction bet#een t"em "old t"em into asolid, it is t"en fro+en*

n li uids or gases, t"e speed of t"e particles varies #it" t"e temperature "o#everat eac" temperature some particles #ill move faster t"an ot"ers* !"ose fasterparticles #ill "ave enoug" energy to break a#ay from t"e surface of t"e li uid* $obubbling is seen and t"e li uid slo#ly disappears if t"e li uid is open to t"e air*-oiling is #"en t"e li uid is "eated so strongly t"at t"e particles are moving fastenoug" to break all t"e forces of attraction in t"e li uid*

S"o#ing t"at gases di%use very easily. Put t#o /ars on top of eac" ot"er, onecontaining bromine and t"e ot"er containing air* 0emove t"e lid blocking t"em fromeac" ot"er and you s"ould observe t"at bot" /ars become a very uniform bro#n*

!"is is due to t"e bromine particles bouncing around at random to give an evenmixture*

S"o#ing t"at particles in di%erent gases travel at di%erent speeds. place a piece ofcotton #ool soaked in concentrated ammonia at one end of a glass tube andanot"er piece of cotton #ool soaked in concentrated "ydroc"loric acid* 1 #"iteprecipitate of ammonium c"loride #ould form in bet#een bot" ends. "o#ever it#ould be closer to t"e "ydroc"loric acid* !"is is due to t"e fact t"at ammoniaparticles are lig"ter t"an "ydrogen c"loride particles*

2i%usion in li uids is extremely slo# due to t"e fact t"at t"ere are only small gapsbet#een t"e li uid particles for ot"er particles to di%use into*

0elative c"arge 0elative mass )"ere it is foundProton 34 positive 4 nside t"e nucleus


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'lectron (4 negative 454677 8utside t"enucleus

$eutron 9 5no c"arge5neutral

4 nside t"e nucleus

!"e number of protons in an atom is called t"e atomic number or t"e protonnumber* !"e mass number or t"e nucleon number counts t"e total numbers ofprotons and neutrons in t"e nucleus of t"e atom* sotopes are atoms t"at "ave t"esame atomic number but di%erent mass numbers due to t"em "aving a di%erentnumber of neutrons #"ilst "aving t"e same number of protons and electron:s*

1toms are electrically neutral and t"e positiveness of t"e protons is balance by t"enegativeness of t"e electrons* 1toms are arranged in t"e periodic table in order ofincreasing atomic number*

!"e electrons are found at considerable distance from t"e nucleus in a series oflevels called energy levels or s"ells* &roups contain elements #it" similarproperties* !"eir similarity depends on t"e fact t"at elements in t"e same group"ave t"e same number of electrons in t"eir outer levels*

&roup 6 are considered as being ;full: levels*


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electrons* )"en t"e electron "as been transferred, a sodium ion is left be"ind* !"eattraction of eac" positive ion to t"e delocali+ed electrons "olds t"e structuretoget"er* !"e more electrons being delocali+ed t"e stronger t"e attractions bet#eent"e positive ions and t"e sea of electrons and t"erefore t"e stronger t"e metal*

Forces of attraction bet#een separate molecules are called intermolecular forces* !"ey are muc" #eaker in comparison to covalent or ionic bonds* ntermolecularforces arise from slig"t electrical distortions in molecules* 2uring melting some oft"e intermolecular forces are broken "o#ever in boiling t"e attractions are totallydisrupted and t"e molecules become free to move around as a gas*

&iant metallic structures. t"ey consist of a regular array of positive ions in a sea ofelectrons* !"ey tend to "ave "ig" melting and boiling points due to t"e po#erfulattractions involved* !"ey tend to conduct electricity due to t"e delocali+edelectrons being able to mode t"roug"out t"e structure* !"ey are good conductors of "eat* Metals are easy s"aped due to eit"er regular packing #"ic" allo#s t"em to

slide over eac" ot"er* !"ey are said to be malleable >beaten into s"ape? and ductile>pulled into #ires?* n alloy, t"e di%erent metals "ave di%erent si+ed atoms* !"isbreaks up t"e regular arrangement and makes it more di@cult for t"e layers to slideand t"erefore making t"em stronger*

&iant ionic structures. all ionic compounds consist of "uge lattices of positive andnegative ions packed toget"er in a regular #ay* 1 lattice is a regular array ofparticles* !"ey tend to "ave "ig" melting and boiling points because of t"e strongforces "olding t"e lattices toget"er* !"ey tend to be crystalline* !"ey tend to bebrittle because #"en any force is applied to t"e crystal, t"e crystal #ill be pus"edalong and #ill meet #it" an iron #it" a like c"arge* onic substances tend to besoluble in #ater t"is is because oxygen is slig"tly negative due to electrons beingattracted to#ards it* !"is means t"at #ater is a polar molecule* !"e slig"tly positive"ydrogen cluster around t"e negative ions and t"e negative oxygen are attracted tot"e positive ions* onic compounds tend to be insoluble in organic solvents* !"is isbecause t"e molecules in organic solvents are less polar t"an #ater and t"ereforearen:t strong enoug" to break t"e lattice* onic compounds don:t conduct electricity#"en solid because t"ey don:t "ave any mobile electrons* )"en t"ey are meltedt"ey are able to as t"e ions are free to move*

&iant covalent structures. diamondA in diamond eac" electron is bonded strongly tofour ot"er carbon atoms in a tetra"edral arrangement* t is very "ard #it" "ig"melting and boiling point because of t"e strong carbon to carbon covalent bonds*2iamond doesn:t conduct electricity because all of t"e electrons in t"e outer levelsof t"e carbon atoms are tig"tly "eld in covalent bonds and t"erefore means t"att"ey aren:t able to move* 2iamond doesn:t dissolve in #ater or any ot"er solventbecause t"e carbon to carbon bonding is too strong and can:t be broken by anysolvent*


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&rap"iteA t is a soft material #it" a slimy feel because t"e attractions bet#een t"elayers are muc" #eaker and can t"erefore be Baked o% and t"erefore is used inpencils* t "as a "ig" melting and boiling point and is insoluble in any solventsbecause it "as very strong covalent bonds* &rap"ite is less dense t"an diamondbecause t"e layers in grap"ite are relatively far apart and t"is means t"at grap"ite

crystals "ave a lot of #asted space in comparison to diamond crystals* &rap"iteconducts electricity because grap"ite "as an extra delocali+ed electron #"ic" isable to conduct electricity*

Simple molecular structuresA !"ey tend to be li uids, gases ore solids #it" lo#melting points due to t"eir #eak intermolecular attractions* !"ey tend to beinsoluble in #ater unless t"ey react #it" it because t"e intermolecular forcesbet#een #ater are too strong and can:t be broken t"at easily* Molecular substancesare often soluble in organic substances* Molecular substances don:t conductelectricity*

For a c"emical reaction to occur, t"e reactant particles must collide* Collisions #it"too little energy do not produce a reaction* !"e collision must "ave enoug" energyfor t"e particles to react* !"e minimum energy needed for particles to react is calledt"e activation energy*

C"anging concentration or pressure

f t"e concentration of a dissolved reactant is increased, or t"e pressure of areacting gas is increasedA

!"ere are more reactant particles in t"e same volume* !"ere is a greater c"ance oft"e particles colliding* !"e rate of reaction increases*

C"anging particle si+e

f a solid reactant is broken into small pieces or ground into a po#derA

ts surface area is increased* More particles are exposed to t"e ot"er reactant* !"ereis a greater c"ance of t"e particles colliding* !"e rate of reaction increases*

C"anging t"e temperature

f t"e temperature is increasedA

!"e reactant particles move more uickly* More particles "ave t"e activation energyor greater* !"e particles collide more often, and more of t"e collisions result in areaction* !"e rate of reaction increases*

sing a catalyst


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Catalysts increase t"e rate of reaction #it"out being used up* !"ey do t"is bylo#ering t"e activation energy needed* )it" a catalyst, more collisions result in areaction, so t"e rate of reaction increases* 2i%erent reactions need di%erentcatalysts*

SECTION B: So e esse!tial "ac#$ro%!& c'e istr(

S"o#ing t"at air contains about one( ft" oxygen. use copperA 1dd 499cmD of air in

t"e gas syringe* Pus" it for#ards and back#ards over t"e "eated copper* Stop t"ereaction #"en t"e volume starts becoming constant and #"en t"e copper turnsblack* Eou must cool because t"e air molecules #ould be too "ot* !o nd t"epercentage, subtract t"e volume of air left by t"e initial volume of air and multiplyby 499*

se iron rustingA Put a tube upside do#n lled #it" damn iron #ool and air over abeaker full of #ater* !"e #ater level rises in t"e tube as t"e oxygen is used up* !o

nd t"e percentage, subtract t"e nal volume of #ater by t"e initial volume andmultiply by 499*

8xygen is made in t"e lab by decomposing "ydrogen peroxide using manganese> V? oxide to make #ater and "ydrogen* Eou #ould test for "ydrogen by t"erelig"ting a glo#ing splint*

-urning elements in oxygen. magnesiumA magnesium burns in air #it" a brig"t#"ite Bame to give a #"ite po#der, po#dery as" of magnesium oxide* !"e Bame isextremely brig"t in pure oxygen*


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SulfurA sulfur burns in air #it" a tiny almost invisible, blue Bame* n oxygen it burnsmuc" more strongly, giving a brig"t blue Bame* Poisonous, colorless sulfur dioxidegas is produced*

-urning carbonA carbon burns if it is "eated very strongly in air or oxygen to give

colorless carbon dioxide gas* !"e carbon may produce a small yello#(orange Bameand per"aps some sparks*

Most metal oxides don:t eit"er react #it", or dissolve in, #ater( t"ose t"at do tendto form alkaline solutions* $on(metal oxides often react #it" #ater to form acidicsolutions( common exceptions are #ater and carbon monoxide*

1cid rain is caused #"en #ater and oxygen in t"e atmosp"ere react #it" sulfurdioxide to produce sulfuric acid or #it" various oxides of nitrogen to give nitric acid*

!"ey bot" come from po#er stations and factories burning fossil fuels or from motorve"icles* 1cid rain is #orrying due to its devastating e%ect on trees and on life in#ater* 1cid rain also reacts #it" metals and limestone in nature* !o stop acid rain,you must use catalytic converters to "elp convert oxides of nitrogen into "armlessnitrogen gas* 1 disadvantage of t"is is t"e fact t"at it "as no e%ect on sulfur oxidesand it only #orks #"en it is really "ot*

Making carbon dioxide in t"e lab. react dilute "ydroc"loric acid #it" calciumcarbonate* !o test for carbon dioxide, react t"e carbon dioxide #it" limestone togive you a #"ite precipitate of calcium carbonate* f t"ere is an excess of carbondioxide, t"en t"e precipitate dissolves to give a colorless solution of calcium"ydrogencarbonate*

1 displacement reaction is #"en a more reactive ;metal: displaces or replaces a lessreactive ;metal: from a compound* !"e reactivity series is as follo#s. potassium,sodium, lit"ium, calcium, magnesium, aluminum, carbon, +inc, iron, "ydrogen,copper, silver and gold*

8xidation is t"e gain of oxygen and t"e loss of electrons* 0eduction is t"e loss ofoxygen and t"e gain of electrons* 1 redox reaction is one #"ic" bot" reduction andoxidation are occurring at t"e same time* 1 reducing agent is a substance #"ic"reduces somet"ing else and an oxidi+ing agent is a substance #"ic" oxidessomet"ing else*

Metals above "ydrogen in t"e reactivity series react #it" #ater to produce"ydrogen* f t"e metal reacts #it" cold #ater, t"en metal oxide is formed "o#ever if it is reacted #it" "ot #ater t"en metal "ydroxide is formed* Metals belo# "ydrogenin t"e reactivity series don:t react #it" #ater or steam and t"erefore sometimesused in #ater pipes. copper*

Calcium reacts gently #it" cold #ater to create a #"ite precipitate of calcium"ydroxide #it" "eat* Magnesium doesn:t react #it" cold #ater because as soon as


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t"e reaction starts, magnesium "ydroxide is formed* Since it is insoluble, t"e #atercan:t come into contact #it" t"e magnesium and t"e reaction immediately stops*Magnesium reacts #it" steam to make a brig"t #"ite Bame and produce "ydrogen*

inc and iron react #it" steam to create a yello# solid #"en "ot #"ic" turns into#"ite #"en it is cooled or it reacts to form a slig"tly darker grey to create an oxide

called triiron oxide*

Metals above "ydrogen react #it" acids to form a salt and "ydrogen* Potassium,sodium, lit"ium and calcium "ave very vigorous reactions #it" acids* Magnesiumreacts vigorously #it" cold dilute acids and t"e reaction gets very "ot and forms acolorless solution* 1luminum reacts very slo#ly but after #arming it, t"e reactiongets muc" faster* !"is is because t"e strong insoluble layer of aluminum oxideprevents t"e acid from entering, t"e "eating removes t"is layer* inc and iron reactslo#ly #it" cold acids but more rapidly on "eating*

Finding t"e approximate position of a metal in t"e reactivity series. add a small

piece of metal to cold #ater, if t"ere is any rapid reaction t"en t"e metal must beabove magnesium in t"e reactivity series* f t"ere isn:t any reaction, t"en add asmall amount of metal to some dilute "ydroc"loric acid or sulfuric acid* f t"ere is noreaction t"en it is belo# "ydrogen in t"e reactivity series, "o#ever if t"ere is areaction t"en it is bet#een magnesium and "ydrogen in t"e reactivity series*

niversal indicator is made from a mixture of dyes #"ic" c"ange color in a gradual#ay over a range of P


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1ll acid5metal oxide reactions "ave t"e same ionic e uation. 8=( 3 =


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sulfate crystals* nstead it #ould produce a #"ite po#der of an"ydrous magnesiumsulfate*

Eou al#ays react carbonates and magnesium #it" cold dilute acids and everyt"ingelse s"ould be reacted #it" "ot dilute acids*

For making sodium, potassium and ammonium salts /ust read t"e earlierprocedures* For making sodium c"loride crystals, you don:t leave it to crystalli+e asit "as no #ater of crystalli+ation* For ammonium sulfate crystals you still crystalli+et"em rat"er t"an "eat t"em as "eating #ould break t"e ammonium salts*

For making insoluble salts you use t"e precipitate reaction* t is #"en you react t#osolutions once containing t"e correct positive ion and t"e ot"er correct negative ion*

2o#n#ards p#ards 8ver#ater8xygen $o $o Ees


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litmus paper blue

!esting for carbonates. if you add dilute acid to a solid carbonate t"en carbondioxide is formed in t"e cold* t is best to use nitric acid as some acid(carbonatecombinations can produce an insoluble salt t"at coats t"e solid carbonate and stopt"e reaction* !"e ionic e uation #ould be C8D=( 3 =


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to produce t"e single electrons t"at an atom needs if it is to form simple covalentbonds* !"is is #"y t"ese gases are relatively unreactive*

!"e alkali metals. t"eir melting and boiling points decrease as you go do#n t"egroup* !"eir densities tend to increase and also get softer as you go do#n t"e group

but tarnis" as soon as t"ey are exposed to air* 1ll t"ese metals are extremelyreactive and all react uickly #it" air to form oxides, and react #it" air to formoxides and react #it" #ater to form strongly alkaline solutions of metal "ydroxides*

!o stop t"ese reactions, t"ey are stored under oil and rubidium and caesium "ave tobe stored in sealed glass to stop and oxygen from entering* 1ll t"ese metals react#it" #ater to produce a metal "ydroxide and "ydrogen* SodiumA it Boats due to it"aving a lo#er density t"an #ater and it melts due to it "aving a lo# melting point#"ic" is reac"ed by t"e amount of "eat reacted by t"is reaction* !"e sodium#"i++es as t"e "ydrogen isn:t symmetrically given o%* t also leaves a trail of #"itesodium "ydroxide #"ic" dissolves to make a strongly alkaline solution*

Lit"iumA its melting point is "ig"er compared to sodium and "eat isn:t produced asuickly and t"erefore t"e lit"ium doesn:t melt*

PotassiumA it is muc" faster and enoug" "eat is produced #"ic" t"en ignites t"e"ydrogen to burn #it" a lilac Bame*

0ubidium and caesiumA t"ey react more violently t"an potassium and can beexplosive*

n every single atom in t"is group, t"e outer electron #ill feel an overall attractiveforce of 43 form t"e nucleus, but t"e e%ect of t"e force falls very uickly asdistance increases* !"e bigger t"e atom, t"e more easily t"e outer electron is lost*

Predicting t"e properties of francium. it is very soft #it" a very lo# melting point, itsdensity is about = g5cmD, francium #ill be silvery and #ill tarnis" uickly, #ouldreact very violently #it" #ater to make francium "ydroxide and "ydrogen andfrancium compounds are #"ite and dissolve in #ater to give colorless solutions*


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1ll "alogens react #it" "ydrogen to form "ydrogen "alides* !"ey are soluble in#ater and react #it" it to make solutions of acids* !"e reactivity of t"e "alogensdecrease as you go do#n t"e group* !"e incoming electron is furt"er and furt"erfrom t"e nucleus as you go do#n t"e group, and so it is less strongly attracted* !"atmeans t"e ion is less easily formed and t"at means t"at t"e elements get less

reactive as you go do#n t"e group*

!ransition metals. t"ey are all good conductors of "eat and electricity. t"ey are#orkable, strong and "ave "ig" densities* !"ey are muc" less reactive and don:treact #it" #ater as rapidly* !"ey mostly make colored compounds* 'xample oftransition metals include. iron in t"e manufacture of ammonia, vanadium in t"emanufacture of sulfuric acid and manganese >V ? oxide in t"e decomposition if"ydrogen peroxide*

'lectrolysis is a c"emical c"ange caused by passing an electric current t"roug" acompound #"ic" is eit"er molten or a solution* 1n electrolyte is a substance t"at

undergoes electrolysis* !"ey all contain ions and t"e ions are responsible forconduction of electricity and t"e c"emical c"anges t"at take place* 'lectricity ispassed into and out of t"e electrolyte t"roug" t#o electrodes* Carbon and platinumare examples of electrodes* 1 positive electrode is called an anode and a negativeelectrode is called a cat"ode*

n an ionic compound, t"e solid consists of a giant structure of positive ions andnegative ions packed regularly in a crystal lattice* t doesn:t "ave any mobileelectrons and t"e ions are packed tig"tly in t"e lattice and aren:t free to move* 1ssoon as t"e solid melts, t"e ions become free to move around and t"at enables t"eelectrons to Bo# into t"e circuit* )"en a cation reac"es t"e anode or t"e anionreac"es t"e cat"ode, t"e ions are disc"arged*

$ot all ionic compounds can be electroly+ed molten as t"ey break up into simplersubstances before t"eir melting point* 8t"ers "ave suc" "ig" melting points, it:simpossible to be melted in a lab*

'lectrolysis of a ueous solutions. #ater is a very #eak electrolyte* t ioni+es veryslig"tly it give "ydrogen ions and "ydroxide ions* f t"e metal is "ig"er t"an"ydrogen in t"e reactivity series t"en "ydrogen #ill be made, if t"e metal is lo#ert"an "ydrogen in t"e reactivity series t"en t"e metal #ill be made instead and ifyou "ave a "alogen, t"e "alogen #ill be produced ot"er#ise it #illbe oxygen*

1 reaction t"at gives o% a lot of "eat is said to be exot"ermic*'xamples of exot"ermic reactions include combustion,reactions of metals #it" acids, neutrali+ation reactions andadding #ater to calcium oxide* Ca8 3 8


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n an exot"ermic reaction, t"e reactants "ave more energy t"an t"e products* 1st"e reaction "appens, energy is given out in t"e form of "eat*

1 reaction t"at absorbs energy is said to be endot"ermic* Most carbonates split upto give t"e metal oxide and carbon dioxide #"en you "eat

t"em* n an endot"ermic c"ange, t"e products "ave moreenergy t"an t"e reactants* 2uring c"emical reaction, bonds int"e reactants "ave to be broken and ne# ones formed to maket"e products* -reaking bonds needs energy and energy isreleased #"en ne# ones are made*

1 dynamic e uilibrium is #"en reactions are still continuingand t"ey are al#ays c"anging and never constant*

Le C"atelier:s principle. if a dynamic e uilibrium is disturbed by c"anging t"econditions, t"e reaction moves to counteract t"e c"ange*

0emoving a substance as soon as it is formed #ill cause t"e system to generatemore products* ncreasing t"e pressure on t"e reactants #ill cause t"e system tocreate more products as it #ould #ant to reduce it* f you decrease t"e temperaturefor an exot"ermic reaction t"en t"e system #ill create more products as it #ants tocreate more "eat* 1 catalyst is only added to increase t"e rate at #"ic" e uilibriumis reac"ed*


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SECTION C: Lar$e scale i!or$a!ic c'e istr(

!"e


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acid is t"en made by making adding #ater to t"e sulfuric acid in double amounts*ses of sulfuric acid include making fertili+ers,

making paints and detergents*

!"e c"lor(alkali industry takes sodium c"loride

solution and creates c"lorine, "ydrogen and sodium"ydroxide* !"e cell is designed to keep t"e products apart* f t"e c"lorinecomes into contact #it" sodium "ydroxide solution, it reacts to makebleac"* 1t t"e titanium anode, c"loride ions are disc"arged to producec"lorine gas* 1t t"e steel cat"ode, it is too di@cult to disc"arge sodiumions, so "ydrogen ions from t"e #ater are disc"arged instead to produce"ydrogen gas* More and more #ater keeps splitting up to replace t"e"ydrogen ions as soon as t"ey are disc"arged* 'ac" time #ater molecules splits upit produces a "ydroxide ion as #ell* !"ere #ill t"en be a build(up of sodium ions and"ydroxide ions #"ic" make a solution of sodium "ydroxide* Most of t"e sodiumc"loride crystalli+es out as solid salt* !"is can be separated, redissolved in #aterand recycled back t"roug" t"e cell again*

Sodium "ydroxide is used to purify bauxite to make aluminum oxide and to makepaper by breaking t"e #ood do#n into pulp* t is also used int"e making of bleac" as it is made #"en sodium"ydroxide andc"lorine react toget"er in t"e cold* C"lorine is used tosterili+e #ater, make "ydroc"loric acid and to makebleac"*

Most metals are found in t"e 'art":s crust combined #it"ot"er elements* 1n ore contains enoug" of t"e mineral for it to be#ort"#"ile to be extracted* !"ere are only fe# unreactive metalssuc" as gold and silver #"ic" are found native*

Many ores are eit"er oxides or compounds t"at are easily converted into oxides* !"e"eating of compounds in air to make an oxide is called roasting* !o remove t"emetal from t"e oxide, you t"en "ave to remove t"e oxygen* !"e removal of t"eoxygen is called reduction* Metals exist as positive ions in t"eir ionic compoundsand to produce t"e metal you #ould "ave to add electrons to t"e positive ion, alsokno#n as reduction*


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be used as a source of "eat* 8res of metals "ig"er in t"e reactivity series t"an +inccan:t be reduced using carbon at reasonable temperatures, #"ic" t"erefore makesis extremely dangerous and expensive*

Metals above +inc are usually produced by electrolysis* !"e metal ions are given

electrons directly by t"e cat"ode* nfortunately, large sums of electricity areneeded in t"is expensive process and t"erefore needs muc" more money*

8t"er metals, titanium, need to be extracted by "eating t"e compound #it" a morereactive metal* !"is is more expensive as initially extracting t"e more reactivemetal costs muc" more money*

-ron+e is an alloy of copper tin, bot" of #"ic" are lo# in t"e reactivity series* !"eycan bot" be extracted by "eating t"em #it" carbon* !"ey are extracted #"enstones containing copper or tin ores react #it" res made from c"arcoal*

ron can be made from its ores by "eating t"em #it" carbon, "o#ever at muc""ig"er temperatures* !"e iron produced is also muc" more di@cult to purify*

1luminum is above carbon in t"e reactivity series, it can:t be made accidentally byburning it in air #it" carbon* t "as to be extracted using electrolysis #"ic" neededt"e invention of electricity*

'xtraction of aluminumA

1luminum is t"e most common metal in t"e 'art":s crust* !"e main ore is bauxite*-auxite is rst treated to produce pure aluminum oxide* Since aluminum is areactive metal, it "as to be extracted using electrolysis* Since aluminum "as a very

"ig" melting point, t"e aluminum oxide is dissolved in molten cryolite* Cryolite isanot"er aluminum compound t"at melts at a morereasonable temperature* !"e temperature neededto melt it is 4999 degrees Celsius*

!"e molten aluminum is sip"oned o% from time totime, and fres" aluminum oxide is added to t"e cell* !"e cell operatesat about K( volts, but #it" currents of up to about 499,999 amps*

!"e "eat generated by t"e "uge current keeps t"e electrolyte molten* !"is is

extremely expensive*

1luminum ions are attracted to t"e cat"ode and are reduced to aluminum bygaining electrons.

1lD3 3 De( (I 1l

!"e molten aluminum produced sinks to t"e bottom of t"e cell* !"e oxide ions areattracted to t"e anode and lose electrons to form oxygen gas.


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=8=( (I 8= 3 Ge(

!"is creates a problem, because t"e "ig" temperatures cause t"e carbon anodes toburn #it" t"e oxygen to form carbon dioxide* !"e anodes t"erefore "ave to bereplaced regularly. t"is causes it to be even more expensive*

Pure aluminum isn:t very strong, so aluminum alloys are normally used instead* !"ealuminum can be strengt"ened by adding ot"er elements suc" as silicon, copper ormagnesium* 1luminum:s uses depend on its lo# density and strengt" #"enalloyed, its ability to conduct electricity and "eat, its appearance and its ability toresist corrosion*

'xtraction of ironA

!"e "ot #aste gases at t"e top of t"e furnace arepiped a#ay and used to "eat t"e air blast at t"e bottom* Coke isimpure carbon, and it burns in t"e "ot air blast to form carbon

dioxide* !"is is a strongly exot"ermic reaction*

C 3 9= (I C8=

1t "ig"er temperatures in t"e furnace, t"e carbondioxide us reduced by more carbon to give carbon monoxide*

C8= 3 C (I =C8

t is t"e carbon monoxide #"ic" is t"e mainreducing agent in t"e furnace especially in t"e

pooler parts*Fe=9D 3 DC8(I =Fe 3 DC8=

!"e iron melts and Bo#s to t"e bottom of t"e furnace, #"ere it can betapped o%* n t"e "otter parts of t"e furnace, some of t"e iron oxide is also reducedby carbon itself*

Fe=8D 3 DC (I =Fe 3 DC9=

!"e limestone is added to t"e furnace to remove impurities in t"e ore #"ic" #ouldot"er#ise clog t"e furnace* !"e furnace is "ot enoug" for t"e limestone to undergo

t"ermal decomposition* tsplits up into calcium oxide and carbon dioxide* !"is is anendot"ermic reaction and it is important not to add too muc" limestone to avoidcooling*

CaC8D (I Ca8 3 C8=

Calcium oxide is a basic oxide, and its function is to react #it" acidic oxides suc" assilicon dioxide* Silicon dioxide occurs naturally as uart+*


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Ca8 3 Si9= (I CaSi9D

!"e product is calcium silicate* !"is melts and trickles to t"e bottom of t"e furnaceas a molten slag, #"ic" Boats on top of t"e molten iron and can be tapped o%separately*

Molten iron straig"t from t"e furnace can be cooled rapidly and solidi ed by runningit into sand moulds* !"is is kno#n as pig iron* f t"e pig iron is remelted and cooledunder controlled conditions, cast iron is formed* !"is is very impure iron, containingabout G carbon* Cast iron is very Buid #"en it is molten and doesn:t s"rink muc"#"en it is solidi ed and t"at makes it ideal for casting*

Mild steel is iron containing up to about 9*=K of carbon* !"is small amount ofcarbon increases t"e "ardness and strengt" of t"e iron* t is used for #ires, nails, carbodies and bridges*

)roug"t iron is pure iron* t #as once used to make decorative gates and railings,but t"ey are no# being made by mild steel* !"e purity of t"e iron makes it veryeasy to #ork because it is fairly soft, but t"e softness and t"e lack of strengt"means t"at it isn:t useful for structural purposes*


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Preventing rusting by using barriersA

!"e most obvious #ay to prevent rusting is to keep #ater and oxygen a#ay fromt"e iron* Eou can do t"is by painting it, coating it in grease, covering it in plastic"o#ever as soon as it is broken t"e iron #ill rust* Coating t"e iron #it" a metal

belo# it in t"e reactivity series is /ust a barrier met"od*Preventing rusting by alloying t"e ironA

Eou can turn t"e iron in to stainless steel by alloying t"e iron #it" c"romium andnickel* !"e disadvantage of t"is is t"at it is expensive*

Preventing rusting by using sacri cial metalsA

&alvani+ed iron is iron t"at is coated #it" a layer of +inc* 'ven if t"e layer isscratc"ed, t"e iron is safe because t"e +inc is still more reactive t"an t"e iron andso corrodes instead of t"e iron* 2uring t"e process, t"e +inc loses electrons to form

+inc ionsA

n (I n=3 3 =e(

!"ose electrons Bo# into t"e iron* 1ny iron atom #"ic" "as lost electrons to form anion immediately regains t"em* f t"e iron can:t form ions, it can:t rust* ndergroundpipelines are also protected using sacri cial anodes* n t"is case, sacks containinglumps of magnesium are attac"ed at intervals along t"e pipe*

SECTION D: Or$a!ic c'e istr(

1 molecular formula simply counts t"e number of eac" sort of atom present in t"emolecule, but tells you not"ing about t"e #ay t"ey are /oined toget"er* For examplet"e molecular formula of et"ene is C=


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Prop D-ut GPent K

1lkanes are a family of similar "ydrocarbons in #"ic" all t"e carbons are /oined toeac" ot"er #it" single covalent bonds* Compounds like t"is are coded #it" t"eending ;ane: e*g* et"ane* !"ey are described as being saturated as t"ey contain t"emaximum possible number of "ydrogens for t"e number of carbons*

1lkenes are a family of "ydrocarbons #"ic" contain carbon(carbon double bonds* !"is is represented #it" t"e ending ;ene: e*g* et"ene* !"ey are described as beingunsaturated because t"ey "ave double bonds and t"erefore don:t "ave t"emaximum amount of "ydrogen as t"ere s"ould be*

$ame 2escription-ut(4(ene 1 four( carbon c"ain #it" a double bond

starting on t"e rst carbon-ut(=(ene 1 four( carbon c"ain #it" a double bond

starting on t"e second carbon

'xample of breaking do#n an organic compound nameA

=, D(dimet"ylbut(=(ene

!"e di indicates t"at t"ere are = C


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• Members of a "omologous series "ave similar c"emical properties*

!#o simple reactions of t"e alkanes.

CombustionA all alkanes: burn in air or oxygen* f t"ere is enoug" oxygen, it #ill burncompletely to give carbon dioxide and #ater e*g* C


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Sucrose is broken do#n into glucose and fructose by #ater* C4=


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1ll alco"ols burn to form carbon dioxide and#ater* For exampleA et"anol.

C=


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!"e temperature of t"e column isn:t "ot enoug" to boil some of t"e large"ydrocarbons found in t"e crude oil and t"ey remain as li uid and as removed as aresidue form t"e bottom of t"e column* t also makes -itumen #"ic" is used in roadmaking*

1ll "ydrocarbons burn in air to form carbon dioxide and #ater and also release a lotof "eat in t"e process* !"ey can t"erefore be used as fuels*

1n example is t"e burning of met"ane >natural gas? in airA

C


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Cracking is a useful process in #"ic" large "ydrocarbons are broken do#n intosmaller ones* !"e ma/ority of t"e "ydrocarbons found in crude oil "ave single bondsbet#een t"e carbon atoms* 2uring t"e cracking process, molecules are also formedt"at "ave double bonds bet#een carbon atoms* !"e ne# molecules are muc" morereactive and can be used to make many ot"er t"ings*

!"e gas oil fraction is "eated to give a gas and t"en passed over a catalyst of mixedsilicon dioxide and aluminum oxide at about 999(H999 degrees Celsius* Crackingcan also be carried out at "ig" temperatures #it"out a catalyst*

Cracking is an example of t"ermal decomposition i*e* a big molecule splitting upinto smaller ones on "eating* Cracking produces a mixture of alkanes and alkenes*1n example #ould include.

C4D


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C"loroet"ene is an et"ene molecule #"ere one of t"e "ydrogen atoms "as beenreplaced #it" a c"lorine atom* Polymeri+ing C"loroet"ene gives you poly>C"loroet"ene?*

Poly >C"loroet"ene? "as many uses* t is uite strong and rigid and is t"erefore used

for drainpipes or replacement #indo#s* t can also be mad Bexible by adding;plasticisers:* !"is t"en makes it useful for Boor coverings and even clot"ing*

$ylon is di%erent to addition polymeri+ation as instead of "aving one monomer. youoften "ave t#o, /oining toget"er alternately* 'ac" time t"e t#o monomers combine,a small molecule is lost* !"is is called a condensation reaction*

8ne of t"e monomers is a six(carbon organic acid #it" a NC88< group at eac" endcalled "exanedioic acid* !"e NC88< group is kno#n as carboxylic acid group* t ispart of a family of compounds called dicarboxylic acid* !"e formula is.


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SECTION E: C'e istr( calc%latio!s

1toms are extremely small* n order to get 4 gram of "ydrogen, you need *9=x49R=D atoms* t #ould be too "ard to measure t"e masses of atoms inconventional mass units suc" as grams. t"ey are instead measured in comparisonto t"e carbon(4= isotope* 8n t"is scale, one atom of t"e carbon(4= #eig"s exactly4= units*

!"e relative atomic mass of an element is given t"e symbol 1r or 01M* !"e relativeatomic mass of an element is t"e #eig"ted average mass of t"e isotopes of t"eelement* t is measured on a scale on #"ic" a carbon(4= atom "as a mass of exactly4= units*

!"e #eig"ted average is t"e percentage abundance of an atom in t"e #orldmultiplied by its atomic mass* For example for C"lorine DK "as HK abundance#"ilst C"lorine DH "as =K abundance.

>DK x HK5499? 3 >DH x =K5499? O DK*K

!"e abundance data mig"t also be given in grap" form*

0elative molecular mass is only used for substances #"ic" are actually molecules,basically covalent substances and t"erefore can:t be used for ionic substances*0elative formula mass is used for #"en talking about compounds*

0elative formula mass is given t"e symbol Mr*

!o nd t"e relative formula mass, you must add all of relative atomic masses of allof t"e di%erent elements* Eou get t"e relative atomic masses from t"e periodictable* For example for MgC8D.

Mg 3 C 3 >8 x D? O=G 3 4= 3 >4 x D? O 6G

!o nd t"e percentage composition of an element in a compound, you divide t"eatomic mass of t"e element you are looking for and divide it by t"e relative formulamass of t"e compound* For example t"e percentage by mass of copper in copper > ?oxide, Cu8.

0FM of Cu8 O G 3 4 O 69


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G569 x 499 O 69

!"e mole is a measure of amount of substance* 1 mole is a particular mass of t"atsubstance* !o nd t"e mass of 4 mol of a substance, you must #ork out t"e relativeformula mass and /ust attac" grams at t"e back* For example 4 mole of oxygen.

0elative atomic mass O 4

0elative formula mass O 4 x = O D=

4 mole of oxygen atoms O 4

4 mole of oxygen molecules O D=

$umber of moles O mass5 0FM

For example t"e mass of 9*= moles of calcium carbonate.

0FM of CaC8D O G9 3 4= 3 >D x 4 ? O 499g

4 mole of CaC8D O 499g

Mass O number of moles x 0FM O 9*= x 499 O =9 g

4 mole of anyt"ing contains t"e same number of particles, 1vogadro:s constant* Soevery mole contains *9= x 49R=D particles*

Suppose =*G g of magnesium combined #it" 4* g of oxygen* Finding t"e formula ofmagnesium oxideA

Magnesium 8xideCombining masses =*G 4*$umber of moles of atoms =*G5=G 4* 54O 9*4 9*40atio of moles 4 4Simplest formula5empirical formula

Mg 8

1not"er more complicated example.

Mass of empty tube O K=*=g

Mass of tube 3 copper oxide O * g

Mass of tube 3 copper after O K*9g

Mass of oxygen O * N K*9 O 4* g

Mass of copper O K*9 N K=*= O 4=*6g


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Cu 8Combining masses 4=*6g 4* g$umber of moles of atoms 4=*65 D*K 4* 54O 9*= 9*40atio of moles = 4Simplest formula5empirical formula

Cu= 8

Converting empirical formulae into molecular formulae.

Find t"e ratio bet#een t"e elements in t"e empirical formulae* 2ivide t"e mass oft"e compound by 0FM* !"en multiply t"is number by t"e empirical formulae*

)ater of crystalli+ationA #"en some substances crystalli+e from solution, #aterbecomes c"emically bonded #it" t"e salt* !"is is called #ater of crystalli+ation* !"esalt is said to be "ydrated* 1n example is CuS8G*K


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Substitute t"e masses into t"e e uation* 4 mol of CaC8D O 499g produces 4 mol ofCa8 O K g* !"is is info is received from t"e periodic table*

fA 499 g makes K g t"en 4g of CaC8D makes K 5499 calcium oxide O 9*K * !o nd"o# muc" is produced by a certain amount, /ust multiply it by t"e mass being used*

=* Lead is extracted from, PbS* !"e ore is roasted in air to produce lead oxide,Pb8*

=PbS 3D8= (I =Pb8 3 =S8=

!"e lead is t"en reduced to lead by "eating it #it" carbon in a blast furnace*

Pb8 3 C (I Pb 3 C8

a( Calculate t"e mass of sulfur dioxide produced #"en 4 tonne o galena isroasted*

b( !"e mass of lead t"at #ould eventually be produced from t"at 4 tonne ofgalena*

Calculation for part aA

First #rite t"e e uationA

=PbS 3 D8= (I =Pb8 3 =S8=

nterpret t"e e uation in terms of moles* = moles of PbS produce = mol of S8=*

Substitute t"e masses into t"e e uationA =D7g of PbS make Gg of S8=*

f =D7 tonnes of PbS produces G moles of S8= t"en 4 tonne of PbS gives G5=D7 O9*= H tonnes of S8=

Calculation for part bA

First #rite t"e e uationA

=PbS 3 D8= (I =Pb8 3 =S8=

Pb8 3 C (I Pb 3 C8

nterpret t"e e uation in terms of molesA = mol of PbS produces = mol Pb8

= mol of Pb8 make = mol of Pb

So = mol of PbS make = mol of Pb

Substitute t"e masses into t"e e uationA = x =D7 PbS makes =x =9H Pb


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OGH6 PbS makes G4G Pb

f GH6 PbS makes G4G Pb t"en 4 tonne makes G4G5GH6 O 9*6 *

Calculations involving gas volumes

4 litre O 4 dmD O 4999 cmD

1vogadro:s la#A e ual volumes of gases at t"e same temperature and pressurecontain e ual numbers of molecules* !"is means t"at if you 499cmD of "ydrogen atsome temperature and pressure, it contains exactly t"e same number of moleculesas t"ere are in 499cmD of carbon dioxide under t"ose conditions*

4 mol of any gas contains t"e same number of molecules and so occupies t"e samevolume as 4 mole of any ot"er gas at t"e same temperature and pressure*

!"e volume occupied by 4 mole of a gas is called t"e molar volume* 1t room

temperature and pressure, t"e molar volume is approximately =G dmD*4 mol of any gas occupies =G dmD at rtp

Calculating t"e volume of a given mass of gasA

Calculate t"e volume of 9*94g of "ydrogen at rtp*

4 mol of


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!"en 4 g gives =G5499 O 9*=G dmD

So 4 g of CaC8D makes 9*=G dmD of C8=

Problem involving "ydrogenA

)"at is t"e maximum mass of aluminum t"at you could add to an excess of dilute"ydroc"loric acid so t"at you produce no more t"an 499cmD of "ydrogen at rtp*

=1l 3


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!"e percentage yield is t"e amount of product you actually make as a of t"eamount you s"ould t"eoretically make*

Percentage yield O actual yield5 predicted yield x 499

Percentage yields are never 499 , t"is is becauseA

• 0eversible reactions may not go to completion• Some products may be lost• Some reactants may react in an unexpected #ay and t"erefore produce

un#anted products• !"e ra# materials may not be pure and incorrect products #ill t"erefore be

made• Some of t"e products may be left be"ind in t"e apparatus* $ot all of t"e

products #ill be collected• !"e reaction mig"t not be fully completed and not all of t"e reactants "ave

been reacted*

!"e number of coulombs O current x time

4 faraday is t"e uantity of electricity #"ic" presents 4 mole of electrons passing aparticular point in t"e circuit*

4 faraday O 7 ,999 coulombs O 4 mole of electrons

1n example of electroly+ing copper > ? sulp"ate solutionA

)"at mass of copper is deposited on t"e cat"ode during t"e electrolysis of copper> ? sulp"ate if 9*4K amps Bo# for 49 minutesJ

!"e electrode e uation isA Cu=3 3 =e (I Cu

)ork out t"e number of coulombsA

$umber of coulombs O amps x time O 9*4K x 49 x 9 O 79

= moles of electrons give 4 mole of copper

= x 7 999 coulombs give G g of copper

47=,999 give Gg copper

79 coulombs O G547=999 x 79 O 9*9Dg

1n example involving gasesA

!"e electrode e uation isA =


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$umber of coulombs O amps x time O 4 x =9 x 9 O 4=999

Calculating t"e volume of "ydrogenA

=

Chemistry Study Notes Igcse Edexcel

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