SC20 Fuels Flashcards
Define hydrocarbon
A compound made of hydrogen and carbon and is used as a raw material
Why is crude oil finite?
It’s formed underground over millions of years from the buried remains of plants and animals
Top Fraction - Gases
used in domestic heating and cooking
2nd Fraction from top - Petrol
used as fuel in cars
3rd Fraction from top - Kerosene
used as a fuel in aircraft
4th Fraction from top - Diesel
used as a fuel in some cars and larger vehicles eg. trains
5th Fraction - Fuel oil
used as a fuel for larger ships and power stations
6th Fraction - Bitumen
used to surface roads and roofs
How does fractional distillation work?
Crude oil is heated until most of it has turned to gas. The gases enter a fractionating column with a temp. gradient. The longer hydrocarbons have high bps so turn into liquids and drain out the bottom
Why do properties of different fractions differ?
Each fraction has a different length of hydrocarbons, so they each have different properties because of this
Define homologous series
A family of molecules with the same general formula and share similar chemical properties
Why do alkanes form a homologous series?
They all share the same general formula, with a difference of CH2
Define complete combustion
Burning hydrocarbons with plenty of oxygen to produce CO2 and water
Define incomplete combustion
Occurs when a hydrocarbon is burnt with a limited supply of oxygen
Why is carbon monoxide toxic?
It combines with red blood cells and stops your blood from carrying oxygen around the body. This can cause fainting, a coma or even death
Problems with incomplete combustion
It produces carbon monoxide, and carbon in the form of soot
How are harmful products made in incomplete combustion?
Without enough oxygen, the products contain less oxygen, which forms toxic products
How is sulfur dioxide made?
When fossil fuels are burned, they release sulfur dioxide which comes from sulfur impurities in the fossil fuels.
What causes acid rain?
When sulfur dioxide mixes with the clouds, forming dilute sulfuric acid
Effects of acid rain
Causes lakes to become acidic and animals to die. Kills trees, damages limestone buildings and stone statues, and can also make metal corrode
Define oxides of nitrogen
Created from a reaction between the nitrogen and oxygen in the air, caused by the energy released by combustion reactions
What do oxides of nitrogen cause?
Contribute to acid rain, and cause photochemical smog that causes air pollution
Advantages to using Hydrogen as a fuel
- Clean fuel
- Only waste product is water
- Renewable
Disadvantages to using Hydrogen as a fuel
- Need a special, expensive machine
- Expensive
- Uses energy from other sources (energy often from burning fossil fuels)
Define cracking
Cracking turns long saturated alkane molecules into smaller unsaturated alkene and alkane molecules - it’s a form of thermal decomposition
Why are alkanes saturated and alkenes unsaturated?
Alkanes are saturated because all bonds have been formed. Whereas alkenes are unsaturated because all possible bonds that can be formed, haven’t been
Why is cracking necessary?
Cracking helps meet the higher demand for shorter chained molecules, rather than having longer chained molecules that aren’t commonly needed
