Organic Chemistry

Chapter 24Fuels and Crude oil24.1 Introduction - The need for fuel (Tb pg 421)A __________ is a substance that is burnt to produce heat energyToday the two main sources of fuels are ___________________ and ___________________.Coal, petroleum and natural gas are called ___________ _______ because they were formed from the remains of plants and animals that lived a long time ago.

fuelPetroleum /crude oilNatural gasFossil fuels24.2 Petroleum and natural gas (Tb pg 422-423)Petroleum also called ___________ ______ is a thick black liquid.__________ _______ is a colourless gas found together with petroleum in the Earth.

Crude oil Natural gasWhat is petroleum / crude oil?Is a fossil fuel derived from an ancient biomass found in rocksIs a mixtureRecap:A mixture consist of ______________________________________________________Mixtures can be separated by physical methods such as ____________, ___________________, ________________and for crude oil, _________________________two or more elements or compounds not chemically combined togetherfiltrationchromatographydistillationFractional distillationWhat is petroleum/ crude oil?Is a fossil fuel derived from an ancient biomass found in rocksIs a mixtureContain a very large number of compoundsConsist mainly HYDROCARBONS (Hydrocarbons are compounds made up of _____________ and ________ only.)Also contains sulfur or sulfur compounds

hydrogencarbonPetroleum / Crude oilHow was it formed?From organisms which lived millions of years agoTheir remains were covered by layers of sedimentary rocksHeat and pressure in the absence of air converted the remains into fossil fuels

Gas and oil is trapped underground They cannot pass through the non-porous layersCombustion of petroleum and natural gas________________ is the main constituents of natural gas.Petroleum and natural gas when burnt provides energy. When they are completely burnt in air, the products are __________ ___________ and ___________If insufficient air is present, combustion is incomplete and _________ ___________ and ________ are also obtained.

MethaneCarbon dioxidewaterCarbon monoxideCarbonPetroleum / Crude oilHow is it processed?Crude oil can be split into fractionsFractions group of compounds with similar boiling pointsThe process is called fractional distillation

24.3 Fractional distillation of petroleum (Tb pg 424-425)What is petroleum? Petroleum is a mixture of ________________ that has to be separated into useful fractions by _____________ ___________ before it can be used. The petroleum gas fraction that comes out of the top of the column has the _________ boiling point

hydrocarbonsFractional distillationlowest

Fractional distillationWhat happens?Crude oil is fed into the furnace and heated until it turns into gas.Inside the fractionating column the fractions condense and come out of the column at different heights depending on their boiling points. P

P

N

K

D

L

BPetroleum gas

Petrol

Naphtha

Kerosene

Diesel oil

Lubricating oil

BitumenAll the fractions are insoluble in ________ and burn in air.As boiling points increase, The molecules become _____________The liquid becomes more __________They burn less easily with a smoky flame.

waterbiggerviscousViscous = not very runny (a bit like syrup) Fractions and their uses

Petroleum gasPetrolNaphthakeroseneDiesel oilLubricating oilBitumenFuel for cookingFuel for motorcarsFuel for jet aircraftFuel for diesel enginesLubricant for machine, waxes and polishesRoads and roofsFractional distillationWhat happens to the fractions?Fractions are still mixturesDifferent fractions are put to different usesFractions can be distilled furtherSome fractions are more valuable than othersThe heavier fractions are less valuableLarger molecules can be broken down into smaller ones this is known as cracking CrackingWhy is it done?Larger hydrocarbon molecules are less usefulThey can be broken down into smaller moleculesSmaller molecules are more usefulCrackingWhat happens?Large hydrocarbons are vaporised (turned into gas)The vapors are passed over a hot catalystBonds are broken and smaller molecules are madeThermal decomposition (breaking up by heating) takes placeCatalysts help speed up reactions

CrackingWhat happens?Many different hydrocarbons are produced because the molecules can break down in different ways