IGCSE Chemistry WorkbookAnswerso1 The particulate nature of matterCore1 aiii when a solid changes directly to a gas,orvice versa [1]9080iv when a gas changes into a liquid [1]10v when a liquid changes into a gas [1]60vi when a solute 'disappears'into a solvent to50form a solution [1]40b i condensation [1]30ii melting [1]20iii sublimation (1]100iv dissolving [1]-100203040506070Core/Extendedtime/min4 a Diffusion cannot occur in solids because[1 for scale,1 for axis labels and units,1 forthe particles are bonded to each other morepoints plotted correctly,1 for line]strongly than those in liquids and gases,which do diffuse.[1]This prevents them frombeing able to move relative to one another.[1]c82C1]b Gases can be compressed more than liquidsd The particles move around more as they gainbecause the particles in the gas are much morekinetic energy.[1]This breaks more of thespread out than those in a liquid.[1]Thisinter-particle bonds,allowing the particles tomove away from each other.[1]means that the gas particles can be squeezedtogether more than those in a liquid,which are2 In ice,I (the water molecule)am bonded to othermuch closer to one another.1water molecules and vibrating in a fixed position.[1]c Liquids can flow because their particles haveAs the temperature rises,there is enough energy formuch weaker bonds between them than thosesome of the bonds between us to weaken and beginin a solid.[1]This means that the particles in ato break due to the increase in vibrations.1/Thisliquid can move over one another.[1]allows me to move further from my neighbouringmolecules and I am able to move past them.[1]AsExtendedthe temperature continues to rise,more of the bonds5 aammonia[1]between us begin to break and I move away fromb point B[1]Both HCland NH,particles movemy neighbouring molecules and move much morequickly.[1]At 100CI have so little attraction torandomly along the tube,but the ammoniamy neighbouring molecules that I am able to breakpartides are lighter and so will move faster andfurther along the tube than the HCl partides.[1]away [1]and move a long way away from them.[1]3 a i when a substance changes from a solid to arandomly [1]liquid (1]Exam focusii when substances are changed into different1 a i Solid-any two of:cannot be compressed,substances by chemical reaction /1has a fixed shape,expands on heating [2]Liquid-any two of:will flow and takeCambridge IGCSE Chemistry Workbook Answers Hodder Stoughton Ltd 2015Answersup the shape of the container,can only beincreases when heated 2]Gas -any two of:compressed a small amount,its volumeis easily compressed,flows easily will fillthe whole volume of its container [2]iisolidliquidgas[1 for each]bi-39℃[1d Water vapour inside the house,causedii oxygen [1]by central heating,hot water and peopleiii phosphorus and iron [1]breathing [1],condenses onto the glass of thewindows,which is colder.1]iv bromine [1]e At the bottom of the ocean the bubble has a2 a Gas particles from the coffee are movinglarge amount of pressure all around it due torandomly from the coffee shop,colliding withthe depth of water,and has an equal interiorother particles in the air,until they reach you.pressure caused by methane molecules.[1][1]They are diffusing.[1]As the bubble rises,the external pressureb When the temperature rises,the steel tracksdecreases and the relative greater interiorwill expand.[1]The gaps allow the tracks topressure of the gas in the bubble causes theexpand without buckling the railway lines.[1]volume of the methane bubble to increase.[1]c The particles of tea move randomly andf i moving randomly around [1]collide with water molecules in the water.[1]ii The pollen grains would be movedThey diffuse from the tea bag until eventuallyrandomly by water molecules collidingall of the water in the cup changes colour aswith them.[1]The dust particles wouldthe tea dissolves.[1]be moved randomly by colliding withmolecules and atoms in the air.1]O2 Elements,compounds and experimentaltechniquesCore1 a substances A and E [1 for each]b substances C and D[1foreach]iv false [1]c substance B 1]v true 1]d substances B and D [1 for each]vi false [1]e substance D [1]vii true 1]f substance B[1]3 a The elements in a compound,e.g.iron sulfideg substance E[1][1],cannot be separated by physical means2 a Accept any sensible answer with a reasonable[1],whilst a mixture of iron filings and sulfurexplanation,for example:powder can be separated using a magnet.[1]iC [1],C is a non-metal [1]b i carbon monoxide,sulfuric acid,methane,sodium hydroxide,limestone 1 for eachii iron [1],iron is a metal [1]ii stainless steel,lemonade,cement,beer,brassiii Na [1],its symbol is related to the Latin[1 for each]name[1]c Accept any sensible answer with a reasonableb i false [1]explanation,for example:ii true [1]Cambridge IGCSE Chemistry Workbook Answers Hodder Stoughton Ltd 2015Answersi water [1],water is a compound [1]b i 2Pb(s)+O,(g)2PbO(s)[1 for products,ii chromium [1],chromium is an element [1]1 for reactants]iii F,[1],F,is an element [1]4 a i Use safety spectacles [1]to protect eyes.[1]1 for reactants]ii A new substance is being produced.[1]iii C,H,(g)+30,(g)2CO,(g)+2H,O(1)[1 forproducts,1 for reactants]iii zinc oxide [1]iv 2Fe(s)+3Br,(1)>2FeBr (s)[1 for products,1 for reactants]Z☑n(s)+S(s)→ZnS(s)[1 for reactants,1 for products]v CuO(s)+2HCI(aq)CuCl,(aq)+H,O(1)[1 for products,1 for reactants]v Zinc and sulfur can be separated byphysical means(e.g.using an organicvi SnO,(s)+2H,(g)Sn(s)+2H,O(l)[1 forsolvent to dissolve the sulfur)[1]whereasproducts,1 for reactants]the compound zinc sulfide [1]needs6 a i 1 thermometer,2 cold water out,3 coldchemical means to separate the elements.[1]water in,4 fractionating column,5 heat,vi three (or more)from:food flavouring,de-6 distillate,7 mixture of liquids,8 Liebigicer on roads,in water softening,to makecondenser [1 for each]dyes fast,in soap manufacture,in curing ofii crude oil [1],the fractions within theanimal hides 3]mixture have different boiling points [1];b i copper,oxygen,carbon [1 foreac]air [1],the gases in the mixture that is air allhave different boiling points[1]ii copper sulfide,copper oxide,sulfur dioxide,carbon dioxide [1 for each]b 1 chromatography paper,2 beaker,3 pencilline,4 solvent,5 samples [1 for each]iii copper sulfide oxygen-copper oxidesulfur dioxide 1]c How close each measurement is to the true2CuS(s)+30,(g)2CuO(s)+2S0,(g)value.1/It depends on the quality of the[1 for reactants,1 for products,1 for correctmeasuring apparatus(e.g.the thermometerbalancing]or electronic balance)and on the skill of thescientists taking the measurement.[1]dioxide [1]d i Time:hours [1],minutes [1],seconds [1]2CuO(s)+C(s)2Cu(s)+CO,(g)ii Temperature:degrees Celsius [1][1 for reactants,1 for products,1 for correctiii Volume:cm3 [1],litres [1]balancing]iv Mass:grams [1],kilograms [1]5 ae i one hundredth of a second [1]Formula ofTotalsubstanceii one tenth of a degree [1]SymbolNameNumber ofnumberof atomsatomsiii one hundredth of a gram [1]LiNO,Lithium15iv one tenth of a cm3 1]NNitrogen10Oxygen3ExtendedCaCalcium157 a a reaction that involves the processes of bothcCarbon1oxidation 1]and reduction 1]03b i coke (carbon)[1]MgMagnesium35ii zinc oxide 1]NNitrogen2c i zinc oxide [1]AgSilver27ii coke (carbon)[1]CrChromium10d 2ZnO(s)+C(s)2Zn(s)+CO,(g)4[1 for reactants,1 for products]AlBr CsAlAluminium16e i carbon,hydrogen 1 for eachBrBromine4CsCaesium1ii lead oxide,tin(Iv)oxide [1 for each]iii lead oxide,tin(Iv)oxide [1 for each]Cambridge IGCSE Chemistry Workbook Answers Hodder Stoughton Ltd 20153