Hydrogen & Fossil Fuels

Specification Point 8.14:

• Evaluate the advantages and disadvantages of using hydrogen, rather than petrol, as a fuel in cars

• Hydrogen is used in rocket engines and in fuel cells to power some cars.
• It reacts with oxygen in an exothermic reaction:

2H₂ + O₂ →2H₂O

• Hydrogen has a series of advantages and disadvantages regarding its use as a fuel:

• Advantages:
  • It releases more energy per kilogram than any other fuel (except for nuclear fuels).
  • It does not pollute as it only produces water on combustion, no other product is formed.
  • It is a renewable source and is extracted from water by electrolysis.
  • Modern fuel cells are equipped to extract hydrogen from the same water they produce.

• Disadvantages:
  • Expensive to produce and requires energy for the production process.
  • Difficult and dangerous to store and move around (usually stored as liquid hydrogen in highly pressurised containers).

Specification Point 8.15:

• Recall that petrol, kerosene and diesel oil are non-renewable fossil fuels obtained from crude oil and methane is a non-renewable fossil fuel found in natural gas

• Non-renewable fossil fuels are obtained from crude oil by fractional distillation.
• Petrol is used as a fuel in cars, kerosene is used to fuel aircraft and diesel oil is used as a fuel in some cars, trucks and heavy vehicles such as tanks and trains.
• There are finite amounts of all three and they all contribute to pollution and global warming.
• Natural gas consists mainly of methane, CH₄
• This is also a non-renewable fuel as there are finite reserves available.