5.22 understand that nitrogen from air, and ydrogen from natural gas or the cracking of hydrocarbons, are used in the manufacture of ammonia

Ammonia is manufactured using hydrogen and nitrogen (as ammonia is NH₃). The equation for the reaction is...

N_{2 (g)}  + 3H_{2 (g)} ⇌  + 2NH_{3 (g)} (+heat)

Hydrogen is sourced from natural gas. Nitrogen is sourced from the air (as the air is 78% nitrogen).

The manufacture of ammonia with hydrogen and nitrogen is reversible, therefore, as soon as ammonia is made, it starts to turn back into nitrogen and hydrogen. This mean that not all of the nitrogen and hydrogen is converted to ammonia and not all ammonia is converted into nitrogen and hydrogen (because, as soon as nitrogen and hydrogen are produced, it starts to turn into ammonia). This means the reaction reached a dynamic equilibrium.

5.21 understamd that condensation polymerisation produces a small molecule, such as water, as well as the polymer

When condensation polymerisation occurs, a small molecule (such as water) is produces, as well as the monomer.

5.20 understand that some polymers, such as nylon, form by a different process called condensation poymerisation

Most often, condensation polymerisation involves two different types of monomer. These monomers react together forming bonds between them, making polymer chains. However, for each new bond that forms, a molecule (e.g. water) is lost.

5.19 explain that addition polymers are hard to dispose of as their inertness means that they do not easily biodegrade

Most addition polymers are inert. All this means is that they do not react easily (due to the fact that the carbon bonds are very strong and hard to break). This means that it takes a really long time for addition polymers to biodegrade. Furthermore, burning plastics releases toxic chemicals so that's not a good idea either. Because of this, it is hard to dispose of polymers (that's why we recycle them).

5.18 describe some uses for polymers, including poly(ethene), poly(propene) and poly(chloroethene)

Polyethene is light and stretchy making it ideal for packaging such as plastic bags, water bottles/food containers and carpets.

Polypropene is a tough polymer but is quite flexible and heat resistant too, this makes it ideal for making things like crates

Polychloroethene is used to make clothes, drainpipes and insulating cables

5.17 deduce the structure of a monomer from the repeat unit of an addition polymer

To find the structure of a monomer, take the repeat unit of an addition polymer and add a double bond between the two carbons.

5.16 draw the repeat unit of addition polymers, including poly(ethene), poly(propene) and poly(chloroethene)

To find the repeating unit, just find the section of the polymer that is repeated and draw it out, writing the number of monomers there are next to it (if you don't know how many monomers there are, you must put an 'n')...

Polyethene


Polypropene

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Polychloroethene

image credit: wiki // quizlet

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5.15 understand that an addition polymer is formed by joining up many small molecules called monomers

A polymer is just a very long saturated chain (saturated as it has no carbon double bonds). Small molecules called monomers join together to make polymers. One type of polymer is an addition polymer. The monomers that make up addition polymers are alkenes as they have a carbon-carbon double bond. If alkenes are put under a high pressure with a catalyst, they will break their carbon-carbon double  bond and polymerise (join together), forming a polymer.

5.14 describe how lng-chain alkanes are converted to alkenes and shorter-chaiin alkanes by catalytic cracking, using silica or alumina as the atalyst and a temperature in the range of 600-700°C

If carrying out the reaction in a lab...
1- Heat the hydrocarbon (e.g. paraffin).
2- After a few seconds, move the Bunsen burner to heat the silica/aluminium catalyst
3- Alternate between the two until the paraffin vaporises and the catalyst glows red
4- The heated paraffin vapour cracks as it passes over the heated catalyst
5- small alkanes collect at the end of the boiling tube, while alkene gases travel down the delivery tube
6- The alkenes are collected through water using a glass jar


In industry, vapourised hydrocarbons are passed over a powdered catalyst at about 600-700°C. silica and aluminium are used as catalysts.

Notes credit: CGP

5.13 understand that fractional distillation of crude oil produces more long-chain hydrocarbons than can be used directly and fewer short-chain hydrocarbons than required and explain why this makes cracking necessary

Fractional distillation produces lots of long chain hydrocarbons and not many short chain hydrocarbons in relative. The short chain hydrocarbons are useful but long chain hydrocarbons are not. This means we have to break the long chain hydrocarbons into short chain hydrocarbons as demand for short chain hydrocarbons is high. This is done in a process known as cracking. This process is a form of thermal decomposition, which just means breaking down the molecules into simpler molecules by heating them.

5.12 understand that nitrogen oxides and sulfur dioxide are pollutant gases which contribute to acid raid, and describe the problems caused by acid rain

Sulfur dioxide mix with clouds forming dilute sulfuric acid, which is very acidic. Nitrous oxide also mixes with clouds, forming nitric acid. These fall as acid rain which causes lakes to become acid in (killing plants and animals), kills trees and damages limestone buildings and statues.

There have also been links made between acid rain and human health although these are not proven.

5.11 understand that, in car engines, the temperature reached is high enough to allow nitrogen and oxygen from air to react, forming nitrogen oxides

In car engines, crude oil fractions (such as diesel or petrol) are burnt (as fuels). When fossil fuels are burnt, nitrogen oxide and sulfur dioxide are always released, always. When the temperature is high enough, the nitrogen and oxygen in the air react (this creates nitrous oxides, such as nitrogen monoxide and nitrogen dioxide).

NOTE: remember nitrogen oxide and sulfur dioxide are always produced when fossil fuels are burnt.

5.10 understand that incomplete combustion of fuels may produce carbon monoxide and explain that carbon monoxide is poisonous because it reduces the capacity of the blood from air to react, forming nitrogen oxides

First of all, incomplete combustion just means that the substance/thing was burnt without lots of oxygen present. When hydrocarbon fuels (for example gas or petrol) is burnt without oxygen, carbon monoxide is produced (as apposed to carbon dioxide, with complete combustion). This is bad because carbon monoxide is poisonous. This is because it combines with haemoglobin (this carried oxygen in your blood), preventing as much oxygen to get to your cells (as less oxygen can bind with the haemoglobin as there is lots of carbon monoxide combined with the haemoglobin). Therefore, less oxygen is being carried around your body (in your blood), this can lead to fainting, a coma or even death (in severe circumstances) as your cells are effectively being starved of oxygen.

5.9 describe the trend in boiling point and viscosity of the main fractions

The lower the boiling point, the lower the viscosity, and vice versa (high boiling point = high viscosity)

NOTE: basically, the lower the viscosity, the thinner the substance runs, the higher the viscosity, the thicker something is (as liquid). For example, water has a super low viscosity, whilst syrup has a higher viscosity than water.

5.8 recall the names and uses of the main fractions obtained from crude oil: refinery gases, gasoline, kerosene, diesel, fuel oil and bitumen

Refinery gases - used in pottery and glass manufacture, heating and bottled gas

Gasoline - used for fuel for cars (its petrol, in other words)

Naphtha - Used as a starting material of making things like plastics,dyes, drugs, explosives and paints (to name a few)

Kerosene - used to fuel jets, in heating and in paint solvents

Diesel - fuel for cars, trucks, trains and boats

Fuel oil - central heating and fuel for really big ships

Bitumen - used to surface roads

5.7 describe and explain how the industrial process of fractional distillation separates crude oil into fractions

NOTE: the process of fractional distillation is mentioned in point 1.7

One use of fractional distillation is separating crude oil into fractions (compounds). Heres how it happens...

- Heat the crude oil until almost all of it has turned into gas, these gases will enter the fractioning column as they evaporate. NOTE: the left over liquid is bitumen, it has a very high boiling temperature so is instead tapped off at the bottom of the column.
- NOTE: in the column there is a temperature gradient. Basically, it is really hot at the bottom and quite bit colder in the top (not actually cold though). This is useful as the substances that make up crude oil have different boiling temperatures, when the substance meets the part of the tube where it is cooler than their boiling temperature, they will condense and drain off down a tube. (NOTE: hydrocarbons with short carbon chains have a low boiling point, so they condense near the top of the fractioning column whilst hydrocarbons with long carbon chains have high boiling points, so they condense near the bottom of the fractioning column.
- This means you result with the different fractions of crude oil (each fraction contains a mixture of hydrocarbons with similar boiling points).

5.6 understand that crude oil is a mixture of hydrocarbons

Hydrocarbons are molecules which contain only hydrogen and carbon atoms. Crude oil is made up of only hydrocarbons (but lots of different types of them).

5.5 explain the uses of aluminium and iron, in terms of their properties

Uses (due to properties) of iron
The properties of iron are all the usual properties of a metal. However, adding something to iron can change its properties (as expected), this means it an be made suitable for many different things. Fir example...
- Pure iron (wrought iron) is malleable ('bendable'), this means it is used to make things such as ornamental gates and railings (as it can be twisted into pretty shapes etc)
- Cast iron (a mixture of iron, carbon and silicon) is very hard, this means it is used to make things such as manhole covers (that undergo lots of pressure, from vehicles, daily) and also some cooking pans
- Steel (an alloy made of iron) is harder than pure (wrought) iron but is still malleable and can also be welded together. It can be easily hammered into sheets and, because of this, it is great for making things that need thin hard metal, such as car bodies and girders for construction.

NOTE: a downside to using iron is that it rusts easily. However, stainless steel (an alloy of iron and chromium) will not rust, because of this, it is used in making things such as cutlery and pans that are exposed to water often (when cleaning etc).

Uses (due to properties) of aluminium
Aluminium is slightly different to iron, it also has all the main properties of a metal however, it doesn't corrode easily. This is because it quickly reacts with oxygen in the air, producing aluminium oxide (which forms as a protective layer around the aluminium, stopping any further reaction taking place) - this stops corrosion.

Due to its non-corroding property, it is used to make products that often come into contact with water (such as coke cans etc).

Aluminium is also a lot less dense than iron, which consequently makes it lighter (less particles per certain area etc), this means it is useful for making things when the weight of a metal frame needs to be taken into consideration (for example, when producing a bicycle frame or aeroplane body)

5.4 describe and explain the main reactions involved in the extraction of iron from iron ore (hematite), using one, limestone and air in a blast furnace

In order to extract iron from hematite (iron ore) you need a blast furnace, coke (for reducing the iron oxide to iron metal) and limestone (for taking away impurities). The process is as follows...



- Hot air is blasted into the furnace (hence name, blast furnace), this makes the coke burn much faster than normal, and also raises the temperature to around 1500ºC. The coke burns to produce carbon dioxide (C + O2 ---> CO2)
- The CO2 then reacts with unburnt/leftover coke, producing carbon monoxide (CO2 + C ---> 2CO)
- The carbon monoxide will then react with the iron ore, producing iron. (3CO + Fe2O3 ---> 3CO2+ 2Fe)
- The limestone removes the silicon dioxide (SiO2) that is the main impurity. This happens as the limestone is decomposed by the heat into calcium oxide and carbon dioxide (CaCO3 ---> CaO + CO2). The calcium oxide then reacts with the silicon dioxide forming calcium silicate, aka slag (CaO + SiO2---> CaSiO3).
- The iron and slag are both molten so sink to the bottom of the furnace. However, slag is less dense than iron so the slag sits into of the iron, they are both tapped off.

NOTE: although the slag is useless in this, the process is still sustainable as the slag is not wasted. It can be used in fertilisers and road building (bit random, i know)

NOTE NOTE: It is very important to understand that this is a reduction reaction (the iron is reduced as it loses oxygen)

image credit: BBC

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5.3 write ionic half-equations for the reactions at the electrodes in aluminium extraction.

If you are looking at this post I assume you know what the electrolysis of aluminium oxide is and the implications, if you do not know, this may help... 5.2

The equations are as follows...

At the anode (positive electrode): 2O²⁻ ---> O₂ + 4e− 

At the cathode (negative electrode): Al³⁺ + 3e− ---> Al