IGCSE›Cambridge IGCSE Chemistry›Mind mapsDiffusionCambridge IGCSE Chemistry: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsWhat is it?Net movement from high to low concentrationMoves down the concentration gradientContinues until particles are evenly spreadNeeds no stirring or outside forceWhy it happensParticles in constant random motionExplained by kinetic particle theoryAcross statesGases: fastest, particles far apart and freeLiquids: much slower, particles close togetherSolids: no diffusion, particles only vibrateDiffusionparticles spreading outNH₃HClMass effectSame temperature → same average kinetic energyLighter particles move faster, diffuse fasterHeavier particles diffuse more slowlyNHX3\ce{NH3}NHX3 (Mr 17) beats HCl\ce{HCl}HCl (Mr 36.5)White ring forms nearer the HCl endTemp and pressureHigher temperature → particles hit walls harder, more oftenHigher pressure → volume decreasesEffects work in both directionsExam tipsExplain with particle motion and collision frequencyNot faster because 'lighter': far apart, free, high energy