Answers toLaboratory Practical BookExperimental skills and abilitiesSkills for scientific enquiry1 (a)measuring cylinder(e)stopwatch(b)digital balance(③digital timer(c)metre ruler(g)ruler(d)liquid in glass thermometer2 (a)Time at least 10oscillations with a stopwatch and divide the result by 10to obtain the average time for one oscillation.(b)Weigh at least 20 pins on a balance and divide the result by 20 to obtain the average mass of one pin.3DeviceAccuracymetre ruler1mmvernier scale0.1mmstopwatchdigital timer1msdigital balancetypically 1g or 0.1gliquid in glass thermometer1.0℃100cm3 measuring cylinder1cm34a)9.75(b9.85 (a)(i)Effect of temperature on rate(ii)Light intensity,concentrations of solutions(i)Manipulated variableFixed variableResponding variabletemperaturelight,concentrationrate of reaction25Y2000246810Rate of reaction(c)Increase in temperature will result in increase in rate of reaction.1 The particulate nature of matter1.1 Rate of diffusion of ammonia and hydrogen chlorideMethod1 To ensure that it is a fair test.2 It would be too difficult to deal with the gases.The gases would begin to diffuse beforethe experiment started.3 Ammonia is toxic.Concentrated hydrochloric acid is corrosive.Results and calculationsStudents should be able to show that the ammonia particles(molecules)have moved along the tube at a faster ratethan the hydrogen chloride particles(molecules).Conclusions1 The longer the tube,the longer the time taken for the white cloud of ammonium chloride to form.This is becausethe rate of diffusion will be slower for both gases.2 The greater the diameter of the tube,the longer the time taken for the white cloud to form.3 Temperature of the laboratory-the higher the temperature the faster the time;concentration of the gases used-the higher their concentration the faster the time;pressure-the higher the room pressure the slower the time.4 Hydrogen chloride end.5 The hydrogen chloride molecules are heavier and therefore have the slower rate of diffusion,so do not travel as faralong the tube as the ammonia particles.EvaluationThe experiment could be repeated to gain an average times and rates.ExtensionThe rate of diffusion is not the same as the speed of the particles.The speed of the particles will be much greater thanthe rate of diffusion.The reason is that the rate of diffusion is lower due to the random collisions between the particleswhich prevent the particles from travelling in straight lines.1.2 Reaction of potassium iodide with lead(II)nitrateMethod1 Because the particles in both solids are vibrating about a fixed point.For the reaction to occur their particlesneed to be forced to collide with one another.Shaking causes this to happen.2 In case,when you are shaking the tube,you hit a bench or other solid object.3 So that there was no contamination of each chemical.ResultsA yellow tinge should be visible on the solid particles,which takes a long time to form.When the two colourless solutions are mixed,a yellow precipitate(solid)forms.If left,the yellow precipitate sinks to thebottom of the tube and a colourless solution is visible above it.2Cambridge IGCSE Chemistry Laboratory Practical Book Doug Wilford Bryan Earl 2015Conclusions1 A yellow tinge on the solid particles.ANSWERS2 Two colourless solutions reacted to give another colourless solution and a yellow precipitate.3 The reaction between the solutions.4 The reaction in Procedure 2 occurred faster because,in solutions,the particles are able to move relative toone another.This allows them to collide more frequently with one another,causing the reaction to occurmore rapidly.5 Colourless.EvaluationIn Procedure 1,the same mass,or,better,the same number of moles of each were used.In Procedure 2,the samevolume of each solution,of the same concentration,could have been used.ExtensionAny one of:1 The shaking could have been more vigorous,resulting in more collisions,and more successful collisions.2 The solids could have been more finely crushed.With a larger surface area,more collisions and more successfulcollisions would occur.3 The experiment could have been carried out at a higher temperature,so particles have more kinetic energy.More collisions and more successful collisions would occur.1.3 Sublimation of iodineMethod1 lodine is harmful.Its fumes are dangerous for the environment.2 To prevent the majority of the iodine vapour from escaping.The iodine vapour returns to a solid on the large,coolsurface area given by the glass wool.3 No.The pressure build up in the tube when the iodine solid changed to iodine vapour would have caused it to beblown off.ResultsMuch of the iodine will have moved from the bottom of the tube to the top.The black/violet solid iodine sublimed on heating to give violet iodine vapour.The iodine vapour returned to its solid form when it reached the cooler parts of the tube.Conclusions1 Black/violet.2 Violet.3 At the top of the tube.The top of the tube is cooler than the bottom and so the iodine vapour sublimes toiodine solid.EvaluationA longer tube could have been usedExtensionAny two from:arsenic,carbon and phosphorus (red).3