GCSE›Edexcel GCSE Chemistry›Mind mapsHydrocarbonsEdexcel GCSE Chemistry: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsAlkanesHydrocarbons: carbon and hydrogen onlySaturated: only C-C single bondsMethane, ethane, propane, butaneCHX4\ce{CH4}CHX4, CX2HX6\ce{C2H6}CX2HX6, CX3HX8\ce{C3H8}CX3HX8, CX4HX10\ce{C4H10}CX4HX10AlkenesContain a C=C double bondUnsaturated: could hold more hydrogenEthene, propene, but-1-ene, but-2-eneCX2HX4\ce{C2H4}CX2HX4, CX3HX6\ce{C3H6}CX3HX6, CX4HX8\ce{C4H8}CX4HX8Bromine reactionAddition: C=C opens, Br adds to each carbonCX2HX4+BrX2→CX2HX4BrX2\ce{C2H4 + Br2 -> C2H4Br2}CX2HX4+BrX2CX2HX4BrX2Product is saturated 1,2-dibromoethaneHydrocarbonsalkanes and alkenesCH4C2H6C2H4Bromine water testAlkene decolourises it: orange to colourlessAlkane: no change, stays orangeAlkane is saturated, cannot add bromineCombustionComplete: hydrocarbon + oxygen → CO2 + waterOxidation reaction that releases energySame products for alkanes and alkenesCX2HX4+3 OX2→2 COX2+2 HX2O\ce{C2H4 + 3O2 -> 2CO2 + 2H2O}CX2HX4+3OX22COX2+2HX2OExam tipsBromine test: state both outcomesBut-1-ene and but-2-ene: same formula, different double bond positionDraw structures showing every covalent bond