Topic 8 - Fuels and Earth Science
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Hydocarbons are
Compounds that only contain carbon and hydrogen
Crude oil is
A complex mixture of hydrocarbons. The hydrocarbons have their carbons arranged in chains or rings Important source of substances called a feedstock for petrochemical industry) A finite resource
Crude oil is seperated by
Fractional distillation
Fractional distillation is
When the oil is heated to a gas then enter the fractionating column where there is a temp gradient. It is hot at the bottom and cooler at the top. The longer hydrocarbons have higher boiling points, so condensate at the bottom. Creates 6 different fractions
The 6 fractions in fractional distillation(top to bottom)
Gases Petrol Kerosene Diesel oil Fuel oil Bitumen
Use of gases fraction
Used in domestic heating and cooking
Petrol fraction use
Fuel for cars
Kerosene fraction use
Fuel in aircraft
Diesel oil fraction use
Fuel in some cars, larger vehicles and trains
Fuel oil fraction use
Fuel for large ships and soem power stations
Bitumen fraction use
Used to surface roads and roofs
The lower the fraction in fractional distillation,
The number of hydrogen and carbon atoms in molecules increase Boiling point increases Ease of ignition decreases Viscocity increases
The hydrocarbons in crude oil are mainly
part of the alkane homologous series
A homologous series is
A family of molecules which have the same general formula and share similar chemical properties. They differ from neighbouring compounds by a CH2 Gradual variation in physical properties
two homologous series’ of hydrocarbons
Alkanes and alkenes
Hydrocarbons are good fuels because
The combustion reactions give out lots of energy. Very exothermic.
When hydrocarbons are burned in plenty of oxygen
Complete combustion occurs, and the only products formed are carbon dioxide and water. Release lots of energy
When hydrocarbons are burned in insufficient oxygen
Incomplete combustion occurs. This produces carbon dioxide and water, but also carbon and carbon monoxide(CO)
Why is carbon monoxide bad
It is toxic as it combines with red blood cells and stops blood carryign oxygen. This can lead to death
Why is carbon bad
Tiny particles of it are relased into the atomsphere, and when they fall they form balck dust called soot. Reduces air quality and makes builidings look dirty
Incomplete combustion occurs in
Some appliances that use carbon compounds as fuels
Sulfur dioxide can be produced by fossil fuels if
They contain sulfur impurities
Sulfur dioxide is bad because
It mixes with the clouds and forms dilute sulfuric acid. This falls as aicd rain
Acid rain is bad because
It causes lakes to become acidic, and many plants and animals die Kills trees, damages limestone buildings and stone statues, and causes metal corrosion