Topic 8.1-8.17 - Fuels

Compounds which only contain carbon and hydrogen

Crude oil is a complex mixture of hydrocarbons, that contain molecules in which carbon atoms are in chains or rings. They are an important source of useful substances (fuels and feedstock for the petrochemical industry) but a finite resource.

-The different hydrocarbons in crude oil each have different boiling points. -Crude oil is heated until it vaporises and enters the fractionating column -The hydrocarbon vapours rise up the column until they condense, doing so at different heights based on their boiling point. -The shortest chain hydrocarbons exit at the cooler top of the column (e.g. gases) and the longest chain hydrocarbons exit at the hot bottom of the fractionating column (e.g. bitumen).

-Gases for domestic heating and cooking -Petrol as fuel for cars -Kerosene as fuel for aircrafts

-Diesel oil as fuel for some cars and trains -Fuel oil as fuel for large ships and in some power stations -Bitumen to surface roads and roofs

As the carbon chain length increases: -Melting and boiling points increase -Viscosity (measure of a fluid’s resistance to flow) increases -The less flammable it is so it is harder to ignite

A series of compounds which have the same general formula but differ by CH₂ in molecular formulae from neighbouring compounds. They have similar chemical properties but show a gradual variation in physical properties, as is displayed by their boiling points — which generally increase as the the number of carbon atoms increase.

A reaction in which carbon dioxide and water are produced and energy is given out. Fuel + O₂ –> CO₂ +H₂O

If there’s not enough oxygen, some of the fuel doesn’t burn. Solid particles of soot (carbons) and unburnt fuel are released. Carbon monoxide is also released when there isn’t enough oxygen to produce CO₂

Carbon monoxide is colourless and odourless. If treated in, it prevents red blood cells from carrying oxygen around the body, which leads to death

-Carbon monoxide is a very toxic gas that causes health problems that lead to death if untreated and is hard to detect. -Soot contributes to global dimming

Sulfur dioxide is a pollutant produced from the combustion of a fuel which contains sulfur impurities with oxygen.

By sulfur dioxide and nitrogen oxides dissolving in rain water

-It damages buildings and statues made with limestone -It reduces the growth of or kills trees and crops -It lowers the pH of water in lakes, killing fish

-High temperatures are reached when fuels are burned in engines. At these temperatures, nitrogen and oxygen from the air can react to produce nitrogen monoxide -This nitrogen monoxide can combine with oxygen in the air to form nitrogen dioxide -Both are oxides of nitrogen and both are pollutants

-Hydrogen only produces water as waste when combusted. No CO² is produced, which contributes to global warming, or other pollutants produced -Hydrogen releases more energy per kg of fuel than petrol -Petrol is from crude oil, a finite resource - hydrogen isn’t a finite resource

-Storage can be dangerous as hydrogen needs to be stored in highly pressurised containers -The manufacture of hydrogen uses large amounts of energy that could release carbon dioxide into the atmosphere

-Petrol, kerosene and diesel oil are non-renewable fossil fuels obtained from crude oil -Methane is a non-renewable fossil fuel found in natural gas

Cracking is a thermal decomposition reaction where larger alkanes are broken down into more useful smaller saturated alkanes and unsaturated alkenes

Smaller hydrocarbons are useful as fuels because they’re more volatile, have lower boiling points and are more flammable than longer chain hydrocarbons