8. Fuels and Earth Science Flashcards
What are hydrocarbons?
Compounds that contain hydrogen and carbon atoms only.
What is crude oil?
- A complex mixture of hydrocarbons.
- Contains molecules with rings of chains of carbon atoms.
- An important source of useful substances like fuels and feedstocks for the petrochemical industry.
- A finite resource.
Where can crude oil be found?
Under the sea and under the ground.
What does it mean when crude oil is described as a ‘finite’ resource?
It will run out.
How can crude oil be separated?
Fractional distillation
How does the process of fractional distillation work to separate crude oil?
- Crude oil is vaporised before it enters a fractionating column.
- The fractionating column is hotter at the bottom that at the top. The vapours rise up and condense at different fractions depending on their boiling points.
- Hydrocarbons with low boiling points will be tapped off the top of the column and hydrocarbons with high boiling points will be tapped off at the bottom of the column.
Why is crude oil separated?
Unseparated crude oil isn’t very useful but the separated products (such as petrol) are very useful.
Refinery gas is a fraction of crude oil. What are its common uses?
Heating and cooking
Which fraction of crude oil is used as fuel in cars?
Petrol.
Diesel is also less commonly used.
Kerosene is a fraction of crude oil. What is a common use of kerosene?
Aircraft fuel
Diesel oil is a fraction of crude oil. What is it commonly used for?
Fuel for some cars and trains.
Which fraction of crude oil is used for road surfacing and roofs?
Bitumen
Fuel oil is a fraction of crude oil. What is it commonly used for?
Fuel for large ships and in some power stations.
How do the hydrocarbons at each fraction differ?
- Boiling points.
- Ease of ignition.
- Viscosity.
- The number of hydrogen and carbon atoms their molecules have.
Where in the fractionating column do hydrocarbons with the highest viscosity condense?
Viscosity is how thick and sticky a substance is.
The hydrocarbons with the highest viscosity (like bitumen) are collected at the bottom of the fractionating column.
What are the properties of hydrocarbons that are tapped from the top of the fractionating column, like petrol and refinery gas?
- Low boiling point.
- Highly volatile.
- Easily ignited.
- Shorter hydrocarbon chains (small molecules).
What is a homologous series?
Series of compounds which:
- Have the same general formula.
- Have similar chemical properties.
- Differ by CH₂ in molecular formula form neighbouring molecules.
- Slight variation in physical properties.
Products from crude oil mostly belong to which homologous series?
Alkane homologous series.
What are the only products when a hydrocarbon fuel undergoes complete combustion?
Water (H₂O) and carbon dioxide (CO₂).
TRUE OR FALSE: Energy is given out when a fuel undergoes complete combustion.
True - the reaction is exothermic.
Write a balanced symbol equation for the complete combustion of ethane.
2C₂H₆ + 7O₂ —> 4CO₂ + 6H₂O
What is complete combustion?
A reaction that occurs when a fuel reacts with excess oxygen.
Write the word equation for complete combustion.
Hydrocarbon + Oxygen —> Carbon dioxide + Water