IGCSE›Cambridge IGCSE Chemistry›Mind mapsPhysical and Chemical ChangesCambridge IGCSE Chemistry: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsPhysical changeNo new substance formedSame substance, e.g. melting ice is still HX2O\ce{H2O}HX2OUsually easily reversibleUsually a small energy changeChemical changeAtoms rearranged into new substancesNew substances have different propertiesUsually hard or impossible to reverseBurning magnesium makes magnesium oxideOften gives heat or lightMeasuring rateTrack change in mass as gas escapesOr measure gas volume with a gas syringePlot amount against timeSteep gradient means fast reactionFlat line means finishedChangesphysical and chemicalRate factorsHigher concentration speeds it upHigher pressure of gases speeds it upLarger surface area speeds it upHigher temperature speeds it upCatalystsIncreases rate, unchanged at the endSame mass before and afterSame amount of product, formed fasterMnOX2\ce{MnO2}MnOX2 catalyses HX2OX2\ce{H2O2}HX2OX2 decompositionExam tipsA catalyst is not used upCatalysts change the rate, not the yield