Fuels And Earth Science Flashcards
How is crude oil separated? How is it formed?
Crude oil is separated into different hydrocarbons to create useful substances. It’s formed underground, over millions of years (at high temperatures and pressures) from the buried remains of plants and animals.
Crude oils fractions:
These are hydrocarbons that contain only hydrogen and carbon, they are mostly alkanes (CnH2n+2). Theses fractions are examples of non renewable fossil fuels.
What are the fractions called?
- gases. >used in domestic heating and coking Glamourous
- petrol. >used as fuel in cars People
- kerosene. >used as fuel for aeroplanes Keep
- diesel oil. >used as fuel for trains and some cars Dogs
- fuel oil. >fuel for large ships For
- bitumen. >to surface roads and roofs Babies
What are alkanes?
It is part of a homologous series which is a family of molecules which have the same general formula and share similar chemical properties.
The first 4 alkanes
Methane>CH4 monkeys
Ethane>C2H6 eat
Propane>C4H8 pink
Brobane>C6H10 bananas
What are the physical properties of hydrogen carbons?
- volatility>higher in smaller chain molecules and lower in larger chain molecules
- ease of ignition>higher in smaller chain molecules and lower in larger chain molecules
- viscosity>lower in small chain molecules and higher in larger chain molecules
- boiling points>lower in small chain molecules and higher in larger chain molecules
- amount of atoms>less in small chain molecules and higher in more chain molecules
Why do hydrocarbons make good fuels?
Because of the combustion reactions that happen when you burn them in oxygen, they are very exothermic, they only produce water and carbon dioxide-this is called complete combustion
What is incomplete combustion?
It is when there is not enough oxygen around for complete combustion. It produces water, carbon dioxide, carbon monoxide and carbon. Carbon monoxide is a toxic gas which can combine with red blood cells and stop your blood carrying oxygen around the body leading to fainting or a coma. Carbon produces soot which is released into the air, reducing air quality causing respiratory problems.
What causes acid rain?
It is caused by sulfur impurities in fossil fuels. When burned they release sulfur dioxide which mixes with the clouds forming a dilute sulfuric acid creating acid rain. Acid rain changes the pH of lakes and soil, effecting wildlife.
What are the pros and cons of hydrogen as a fuel?
-pros
hydrogen is a very clean fuel-only waste product is water
Obtained from renewable sources-not going to run out
-cons
Need special and expensive engine-special skills
Hard to sport-very flammable
What is cracking?
It is splitting long chain molecules into smaller more useful ones. It’s a form of thermal decomposition which is when one substance breaks down into at least two new ones when you heat it meaning breaking strong bonds, needs a lot of energy.
What is does unsaturated mean?
It means that it has a double bond, an alkene is unsaturated. Alkanes are a product of cracking as well as a smaller alkane.
What does cracking do?
It helps meet supply and demand, there is less petrol produced than needed. Cracking allows us to have the correct fuel.
Atmosphere: how did it form?
Phase 1: earth was only molten and had no atmosphere, eventually it cooled leading to a thin crust and an atmosphere of carbon dioxide and water vapour. This water vapour condensed and formed oceans.
Phase 2: a lot of the carbon dioxide dissolved into the oceans and nitrogen was introduced from ammonia and denitrifying bacteria. Green plants removed carbon dioxide.
Phase 3:the build up of oxygen killed off early organisms, it developed the o zone layer, which blocked harmful rays.
How do people effect the air?
human population increases
- more people respiring> less oxygen
- more energy required> burning fuel adds more carbon dioxide
- more land needed>cutting down trees (less oxygen)
