GCSE›AQA GCSE Chemistry›Mind mapsAlkanesAQA GCSE Chemistry: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsWhat are they?Saturated: only single C–C bondsGeneral formula CXnHX2n+2\ce{C_nH_{2n+2}}CXnHX2n+2Main hydrocarbons in crude oilFirst fourMethane CHX4\ce{CH4}CHX4Ethane CX2HX6\ce{C2H6}CX2HX6Propane CX3HX8\ce{C3H8}CX3HX8Butane CX4HX10\ce{C4H10}CX4HX10Getting themFractional distillation of crude oilSeparated by boiling pointSmall alkanes flow easily; large ones are viscousAlkanessaturated hydrocarbonsCHX4\ce{CH4}CHX4CX2HX6\ce{C2H6}CX2HX6CX3HX8\ce{C3H8}CX3HX8Longer chainsBoiling point increasesViscosity increasesFlammability decreasesStronger intermolecular forces to overcomeBurningPlenty of oxygen → complete combustionProducts: CO₂ and water onlyCHX4+2 OX2→COX2+2 HX2O\ce{CH4 + 2O2 -> CO2 + 2H2O}CHX4+2OX2COX2+2HX2OCX3HX8+5 OX2→3 COX2+4 HX2O\ce{C3H8 + 5O2 -> 3CO2 + 4H2O}CX3HX8+5OX23COX2+4HX2OExam tipsBalance C, H and O on both sidesChain length up: boiling point up, flammability downCracking makes large alkanes more useful