Fuels Flashcards
Describe crude oil
- A complex mixture of hydrocarbons
- The carbon atoms can each form 4 covalent bonds, so they can join together in different ways, forming chains and rings
What are the uses for crude oil?
- Fuels for vehicles, aircraft, ships, heating and power stations
- Feedstock
- Petrochemicals
What are petrochemicals?
Substances made from crude oil e.g. poly(ethene) and other polymers
Is crude oil renewable?
No, it is a finite resource - they are being used faster than they are formed
Where does the distillation of crude oil happen?
Fractionating Column
Explain the distillation of crude oil
- The crude oil is heated strongly to evaporate it, and the hot vapours are piped into the bottom of the column
- Fractionating column is hottest at the bottom and coldest at the top, so as the vapours rise, they condense when they reach the part of the column below their boiling point
- The liquid falls into a tray and is piped away
What are the products/fractions of the distillation of crude oil?
FROM TOP TO BOTTOM
Gases - Domestic heating and cooking
Petrol - Fuel for cars
Kerosene - fuel for aircrafts
Diesel oil - fuel for some cars and trains
Fuel oil - fuel for large ships and power stations
Bitumen - surfacing roads and roofs
Explain the trend in the number of atoms different fractions of crude oil
Gases have the smallest number of atoms in molecules (1-4 carbons), so they have the lowest boiling points
Bitumen has the greatest number of atoms in molecules (over 35 carbon atoms), so they have the highest boiling points
The rest are in between in that order
Explain the trend in the viscosity and ease of ignition different fractions of crude oil
Gases - lowest viscosity
Bitumen - highest viscosity
–
Gases - easy to ignite
Bitumen - difficult to ignite
How is bitumen suited to its purpose?
It is a solid at room temperature and waterproof, so it’s good at surfacing roads and roofs
Explain how incomplete combustion can cause problems in appliances that use hydrocarbon fuels
Poor ventilation can cause boilers to release carbon monoxide
Soot can block pipes carrying away waste gases from an appliance, it also blackens buildings and can cause breathing problems if it collects in the lungs
Explain the cause of acid rain
- Hydrocarbon fuels may contain sulfur compounds as impurities
- When the fuel is burnt, the sulfur reacts with the oxygen to form sulfur dioxide gas
- Sulfur dioxide dissolves in the water in clouds to form a mixture of acids e.g. Sulfurous acid
- Mixture of sulfurous acid and sulfuric acid falls as acid rain
What are the problems caused by acid rain?
- Increases rate of weathering of buildings made of limestone or marble, breaking down their structures
- Increases rate of corrosion in metals such as the iron in steel which weakens them
Explain what happens when fuels are burned in engines
- Fuel is mixed with air and ignited inside the engine
- This causes temperatures to be high enough for nitrogen and oxygen in the air to react together
- The reactions produce oxides of nitrogen which are atmospheric pollutants
What does cracking do?
Breaks covalent bonds in hydrocarbon molecules to form a smaller, more useful alkane and an alkene
