SC8: Fuels and Earth Sciences

What is crude oil?

A very useful fossil fuel that is a mixture of many different compounds that are nearly all hydrocarbons.

This contains molecules in which carbon atoms are in the chain.

What are the types of hydrocarbons?

Alkanes and Alkenes

Why is crude oil non renewable?

It is a finite resource

What is a hydrocarbon?

A compound that only contains hydrogen and carbon

Why does fractional distillation work in separating crude oil?

All compounds that make up crude oil have different boiling points.

Describe the process of separating crude oil into simpler compounds.

1. The crude oil is heated in the fractionating column and the oil evaporates and condenses when they reach a level that has a lower temp than the boiling point
2. The fractionating column works continuously, heated crude oil is piped in at the bottom.
3. The vaporised oil rises up the column and the various fractions are constantly tapped off at the different levels where they condense.

What is the use for the fraction: gases?

domestic heating and cooking

What is the use for the fraction: petrol?

fuel for cars

What is the use for the fraction: kerosene?

fuel for aircraft

What is the use for the fraction: diesel oil?

fuel for some cars and trains

What is the use for the fraction: fuel oil?

fuel for large ships and in some power stations

What is the use for the fraction: bitumen?

surface roads and roofs

What is the relationship between the length of hydrocarbon chain and boiling points?

The hydrocarbons with logner chains have higher boiling points and quickly condense back into a liquid as it is not hot enough to keep in gaseous state.

What is the relationship between the length of hydrocarbon chain and vicosity?

As the length of the hydrocarbon chain increases, the viscosity of the substance also increases. This is because longer chains have more intermolecular forces, which require more energy to overcome and thus result in a thicker, more viscous substance.

What is the relationship between the length of hydrocarbon chain and ease of ignition?

The longer the hydrocarbon chain the lower the ease of ignition.

How can you break down long hydrocarbons into smaller hydrocarbons?

Cracking.

What is a homologous series?

Have the same general formula that differ by CH2 in molecular formulae from neighbouring compounds

* Show a gradual variation in physical properties, as exemplified by their boiling points
* Have similar chemical properties

What are the first 4 alkanes?

methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H10)

What is the general formula for an alkane?

CnH2n+2.

Why is an alkane saturated?

There are no double bonds.

What occurs in the complete combustion of a hydrocarbon fuels?

Carbon dioxide is produced and energy is given out as this is an exothermic reaction.

What is produced in the incomplete combustion of hydrocarbons?

If there is not enough oxygen some fuel wont burn creating solid particles of soot (carbons) and unburnt fuel is released. Carbon monoxide (CO) is also released when there isn’t enough oxygen to produce CO2 instead

Why is carbon monoxide a toxic gas?

carbon monoxide is a colourless and odourless gas which, if breathed in, prevents red blood cells carrying oxygen around your body, which leads to death

How is a pollutants like sulfur dioxide created?

Hydrocarbons we burn may have impurities like sulfur. Sulfur is then oxidised to form sulfur dioxide.

* when breathed in it can damage the lungs but when this gas is mixed with clouds it dissolves to make dilute sulfuric acid which falls as acid rain

How is a pollutants like nitrogen oxide created?

Nitrogen and oxygen react in the air but this only occurs at very high temperatures.

when breathed in it can damage the lungs but when this gas is mixed with clouds it dissolves to make dilute nitric acid which falls as acid rain.

What are problems associated with acid rain?

1. Damages buildings and statues (made of limestone)
2. Reduce the growth of or kill trees and crops
3. Lower pH of water in lakes, killing fish

What type of reaction is cracking?

Thermal decomposition

What are the advantages to using hydrogen rather than petrol for fuel in cars?

* Hydrogen is not finite, unlike petrol which is from crude oil.
* This also only produces water – no CO2 produced which contributes to global warming

What is catalytic cracking?

Hydrocarbons can be cracked to produce smaller, more useful molecules.

This process involved heating the hydrocarbons to vaporise them.

The vapours are:

* Either passed over a hot catalyst
* Mixed with steam and heated to a very high temperature so that thermal decomposition reactions can occur.

What is the equation for cracking a long chain alkane?

Long chain alkane → shorter alkane + alkene

Why are alkenes unsaturated?

They have a double bond

What can alkenes be used for?

creating polymers or used to make other chemicals

What happens to a solution of bromine water when n alkene is added to it (test for alkenes)?

Since it is unsaturated and more reactive than alkanes it turns bromine water colourless.

How do alkenes make polymers?

the double bonds break and two or more bonds can be formed

What formed the earths early atmosphere?

There was intense volcanic activity that released gases that formed the early atmosphere.

It was mainly CO2 with little or no O2 (g) but volcanoes also produced nitrogen which gradually built up in the atmosphere (CH4 and NH3)

What did the earths early atmosphere contain?

1. Little or no oxygen
2. A large amount of CO2
3. Water vapour
4. Small amounts of other gases

What formed the oceans?

Water vapour condensed to form the oceans – H2 O (g) -> H2 O (l)

When oceans formed how did CO2 decrease in the atmosphere?

CO2 dissolved in the water and carbonates were precipitated producing sediments, reducing the amount of CO2 in the atmosphere

What is thermal decomposition?

'Thermal decomposition' means to break something down using heat.

What occurs when you heat a metal carbonate?

Metal carbonate  ➔  metal oxide + carbon dioxide

If you heat copper(II) carbonate (which is green) what will happen?

It will decompose into copper(II) oxide, which is black, and carbon dioxide, which is a colourless gas:

How have algae and plants increased O2 in the atmosphere?

Algae & plants produced the O2 that is now in the atmosphere by photosynthesis 6CO2 + 6H2 O -> C6 H12 O6 + 6O2 carbon dioxide + water –(light)-> glucose + oxygen

What is the chemical test for oxygen?

Use a glowing splint inserted into a test tube of the gas and it will relight if oxygen is present

What is the greenhouse effect?

Most wavelengths from the sun passes through the Earth’s atmosphere and while the earth absorbs some radiation and thus warms up, some heat is radiated from the Earth as infrared radiation.

Some of this IR radiation is absorbed by greenhouse gases in the atmosphere and it warms up leading to the greenhouse effect and global warming

What are ​the​ ​potential​ ​causes of climate change ​generated​ ​by​ ​human​ ​activity?

1. Humans produce so much greenhouse gas so this increases the concentration of these gases in the atmosphere leading to more greenhouse effects.
2. Increased consumption of fossil fuels


2. Less photosynthesis leads to more CO2 as deforestation occurs
3. The decomposition of waste by microorganisms can release methane

What are ​the​ ​potential​ ​effects​ ​on​ ​the​ ​climate​ ​of​ ​increased​ ​levels​ ​of​ ​CO​2 and​ ​CH​4​ ​ ​generated​ ​by​ ​human​ ​activity?

Human activity will increase the temperature of the Earth’s atmosphere at the surface and this will result in global climate change.