Fuels and Earth Science (2)

a complex mixture of many different hydrocarbons that is also a finite resource

compounds that contain only hydrogen and carbon

it is formed at high temperatures and pressures from the remains of animals and plants that died millions of years ago

simpler, more useful mixtures than crude oil these contain groups of hydrocarbons of similar lengths

The crude oil is split into separate fractions. 1. The crude oil is heated so that most of it evaporates. 2. It is then pumped into the bottom of a piece of equipment known as a fractionating column. (This fractionating column has a temperature gradient running through it - hottest at the bottom and coldest at the top.) 3. The liquid part (bitumen) is drained off. 4. The gas rises up the column and gradually cools. 5. Different compounds in the mixture have different boiling points, so they condense at different temperatures. This means that they condense at different levels in the fractionating column. 6. The various fractions are constantly tapped off from the column at the different levels where they condense. Hydrocarbons that have a similar number of carbon atoms have similar boiling points, so they condense at similar levels in the column.

surfacing roads and the roofs of buildings

as fuel for large ships and in some power stations

as a fuel in some cars and larger vehicles, such as trains

as fuel in aircraft

as fuel in cars

domestic heating appliances and cooking

a family of molecules which have the same general formula and share similar chemical properties

As chain length increases, so does boiling point. This is because the intermolecular forces of attraction break a lot more easily in small molecules than they do in bigger molecules. A large molecule contains many points along its length where it can be attracted to another molecule. So, even if it can overcome these forces at a few points along its length, it’s still got lots of other places where the force is still strong enough to hold it in place.

As chain length increases, ease of ignition decreases. This is because shorter hydrocarbons have lower boiling points and tend to be gases at room temperature. These gas molecules mix with oxygen in the air to produce a gas mixture that will burts into flames if it comes into contact with a spark.

how easily a substance flows

As chain length increases, viscosity decreases. This is because the stronger the intermolecular forces between hydrocarbon molecules, the harder it is for the liquid to flow.

hydrocarbon + oxygen -> carbon dioxide + water

when they are burned with insufficient oxygen in the air

carbon monoxide and sometimes carbon (in the form of soot)

It binds to the haemoglobin in your red blood cells that normally carry oxygen - so less oxygen is able to be transported around your body. A lack of oxygen in the blood supply to the brain can lead to fainting, a coma or even death.

• makes buildings look dirty • reduces air quality • can cause or worsen respiratory problems appliances that produce soot are inefficient as well as dangerous

• carbon dioxide gas • sulfur dioxide • various nitrogen oxides

It mixes with water in the clouds and reacts with them to form dilute sulfuric acid. This then falls as acid rain. this comes from the burning of sulfur impurities

• causes lakes to become acidic (causing many plants and animals to die) • kills trees • damages limestone buildings • ruins stone statues • can make metals corrode