Chemistry – Production of materials notes 1. Fossil fuels ... – Production of materials notes Chemistry Study Yr 12 HSC Production of Materials 1. Fossil fuels provide both energy
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Chemistry – Production of materials notes
Chemistry StudyYr 12 HSC
Production of Materials
1. Fossil fuels provide both energy and raw materials such as ethylene, for the production of other substances
Identify the industrial source of ethylene from the cracking of some of the fractions from the refining of petroleum
Petroleum is a mixture of hydrocarbons. When petroleum undergoes fractional distillation, there is a higher demand for some fractions due to their high economic value. Other fractions, consisting of larger molecules of low value, can be cracked, breaking the larger molecules (of a similar weight) into smaller molecules. This is how ethylene/ethene is made in industry
Catalytic cracking: Achieved through high temperatures (500 degrees Celsius). Zeolite catalyst. Ethylene is a valuable product of this reaction.Example of catalytic cracking: C10H22(g) C8H18(g) + C2H4(g)
Identify that ethylene, because of the high reactivity of its double bond, is readily transformed into many useful products
Ethenes have double bonds and therefore can be involved in addition reactions. An addition reaction is when there
are no atoms taken away, but there are atoms added. These reactions require a small amount of energy but can be used to create many products.
Identify that ethylene serves as a monomer from which polymers are made Monomer: a small molecule
Polymer: a large molecule made up of a large number of identical monomers joint in chainsPolymerisation: a chemical reaction in which many monomers form a chain called a polymer
Ethylene/Ethene is one example of a monomer, a long chain of many of Ethene monomers is called polyethene
Identify polyethylene as an addition polymer and explain the meaning of this term
Polyethylene is an addition polymer; this means it has been formed from an addition reaction. Where no atoms are taken away, they are only added. This is able to occur as a result of the double bond in ethane/enylene, when the double bond is broken more atoms are can be added on without taking away any atoms, due to the free electrons. The polymer is the only product created.
Outline the steps in the production of polyethylene as an example of a commercially and industrially important polymer
Low Density Polyethylene, LDPE: An initiator known as a peroxide is used to pull an electron out of the
double bond Two extra carbon atoms are added to the chain
This is done at high temperatures and pressures.
The product is branched polythene:This means the molecules are unable to pack closely together, so it is/has-
low density Low mp Relatively soft
High Density Polyethylene, HDPE: Transition metal catalysts are used
This is done at a lower temperature and pressure The product is un-branched polyethylene:This means the molecules can pack closely together so it is/has-
Hard/stiff Higher dencity Higher mp
Linear Low Density Polyethylene, LLDPE: This is a method half way between HDPE and LDPE Metallocene molecules (metal ions sandwiched between two carbon based
rings) used as a catalyst The product still has a large no. of side branches, but the branches are much shorter
Petroleum originates from fossil fuels, there are a number of problems associated with the use of fossil fuels:
Fossil fuels are non-renewable, as a result of the growth in consumption and the increased demand for these resources grow, it has been estimated that many of these will fun out within our generation. Probably between 2025 and 2070
Fossil fuels have a negative impact on the atmosphere, releasing gasses that contribute to the greenhouse effect
Due to these reasons it is important that we become less dependent on Petroleum and use alternate sources of energy, as well as alternate substances that can be used to produce mate rials such as polyethene.
From CSU (just know a few statistics):Petrochemicals are chemicals made from compounds in petroleum or natural gas. Currently Australia has petroleum reserves that will last about ten years and natural gas reserves that will last about one hundred years. Fossil fuels have taken hundreds of millions of years to accumulate. Over 95% of fossil fuel is burnt as a source of energy and once burnt, fossil fuels are no longer available. Less than 5% of fossil fuel is used to make plastics and only a small percentage of that plastic is recycled. If energy and material needs are to be met in the future, alternative sources will be needed as fossil fuel sources are used up.
Explain what is meant by a condensation polymer
Condensation Polymer: when monomers react to form polymers, small molecules are also formed, often water
Describe the reaction involved when a condensation polymer is formed
Condensation Addition
Similarities Joining of monometers to form Polymers
Differences No double bond necessary
Products: Polymer and small molecule
Double bond necessary
Products: polymer
Describe the structure of cellulose and identify it as an example of a condensation polymer found as a major component of biomass
Use available evidence to gather and present data from secondary sources and analyse progress in the recent development and use of a named biopolymer (Polyhydroxyalkanoate PHAs) This analysis should name the specific enzyme (bacteria) used or organism used to synthesise the material and an evaluation of the use or potential use (see below) of the polymer produced related to its properties
Polyhydroxyalkanoate Polymers (PHAs): naturally-occurring polymers produced by bacteria.
Work is underway to determine if they can be grown inside genetically modified plants
How is it produced: There are two methods of production
They are produced by bacteria and can be extracted and processed for many uses.
Genetically-modifying plants to produce PHAs.
Organism or enzyme used to synthesise the biopolymer: Bacteria
Uses: The biopolymers polyhydroxyalkanoate are used in many applications,
including: molded goods paper coatings non-woven fabrics
adhesives, films polymer performance additives
PHAs could replace a significant proportion of the petroleum used today
Why is its production important for society and for the environment? It is a new and another way of forming everyday objects that society use such
as plastics and could possibly replace a large amount of petroleum. This is important for the environment as the petroleum is running out and has
negitive environmental affects.
Benefits include: Development of PHA polymers that compete economically with conventional
fossil-based polymers Improved performance of other biobased polymers through blending with
PHAs
Are there limitations to its commercial viability in the short term? Researchers are still trying to determine whether it can be developed or
grown inside genetically modified plants. They are focused on developing processes for producing PHAs that can
compete with conventional fossil-based polymers. This includes developing improved technologies to extract and process PHAs and PHA blends.
Researchers will also study the fundamental polymer properties of PHA polymers and their blends.
Poly(hydroxybutanoate) PHB
Properties: Stiff Brittle
History: Maurice Limoigne first produced PHB in 1925
How is it produced: PHB can be produced in the lab by feeding bacteria a diet rich nurturance
until large colonies form and then withdrawing glucose. The bacteria automatically start secreting PHB which provides them with an energy store.
In the 1980’s the three genes in Alcaligenes eutrophus needed for the production of PHB were successfully cloned and transferred into E.coli, a common bacteria that was well-researched, reproduced quickly and had an easily manipulated physiology.
Cargill Dow transported the PHB gene into corn and maize plants and allowed crops of PHB-producing plants to be grown and harvested.
Uses: It was first introduced into the medical industry, to make non-toxic and
decomposable structures, and to make plastics in the chemical engineering industry.
Monsanto first put PHB on the shelves in the form of shampoo bottles, but due to costs this was unsuccessful. It could be potentially successful in plastic bags and containers.
Benefits include: Biodegradable Renewable
Are there limitations to its commercial viability in the short term? Expensive
Why is its production important for society and for the environment? It could be used to replace petroleum
New research: For PHBs to be successful it must be able to be produced for less money than
petroleum-based alternatives. Cargill Dow are currently working on the biopolymer being produced by
plants. This could well be the way of the future if they can produce something that is cost effective and maintain the useful properties of the compound.
3. Other resources, such as ethanol, are readily available from renewable resources such as plants
Describe the dehydration of ethanol to ethylene and identify the need for a catalyst in this process and the catalyst used
Describe the addition of water to ethylene resulting in the production of ethanol and identify the need for a catalyst in this process and the catalyst used
Alkanoles: alkanes with one H atom replaced by an OH group The number prefix tells of the location of the OH group
Hydration: the process by which the OH group is added to an alkane
Dehydration: the process by which the OH group is removed from the alkanol
The catalyst used in this process is sulphuric acid/ H2SO4.
Describe and account for the many uses of ethanol as a solvent for polar and non-polar substances
Ethanol is a good solvent for both polar and non-polar substances Ethanol is used as a solvent in: Paints Inks Food colouring Perfumes This is because: C-O and H-O bonds are polar CH3 – CH2 bonds are non polar Ethanol can therefore dissolve both polar and non-polar substance Outline the use of ethanol as a fuel and explain why it can be called a
renewable resource Ethanol can be used as a fuel as it combusts in oxygen to release CO2 H20 and
heat. Ethanol can be made from plant material and the products of its combustion,
carbon dioxide and water, are the reactants needed by plants for photosynthesis, and it can replace itself within the time span of a human life time.
Describe conditions under which fermentation of sugars is promoted Summarise the chemistry of the fermentation process Fermentation must occur with/in: An anoxic environment (no free oxygen)
At the same time, the blue colour of Cu2+ ions disappears and a dark copper coating appears on the nail surface.
The overall reaction is-
Identify the relationship between displacement of metal ions in solution by other metals to the relative activity of metals
A metal higher on the activity series will react when placed in a solution containing a metal lower on the reactivity series. The less active metal being displaced.
The larger the gap in the reactivity series between the metals the more reactive they are
For example: the metals from K to Pb react with dilute acids releasing hydrogen gas the metals from K to Mg react with liquid water the metals from Al to Ni require water to be in the form of steam before
reacting.
Account for changes in the oxidation state of species in terms of their loss or gain of electrons
Note- there has never been a question in the HSC on oxidation no, but still have to know
Oxidation state/ oxidation number: An imaginary number that allows us to see if oxidation or reduction has
occurred.
When a metal reacts with dilute acid and releases hydrogen, the metal undergoes oxidation (loss of electrons) while the hydrogen ions in the acid undergo reduction (gain of electrons).
Example: Magnesium changes from oxidation state 0 to 2. This is an increase, thus this
is oxidation. Hydrogen changes oxidation state from +1 (in H+) to 0 (in the element H2). This is a decrease, thus this is reduction.
It is important to recognise that when a substance acts as a reductant, causing reduction, it is oxidised. When a substance acts as an oxidant, causing oxidation, it is reduced.
There are a few rules that are required while finding the oxidation state. For monatomic atoms the oxidation number is the charge of the ion For a neutral molecule the oxidation state is zero For ions the oxidation state is equal to their overall charge Flourine is always -1 unless it is with halogens or oxygen when it can be
positive Hydrogen is always +1 except with metal hydrides (e.g. LiH) Oxygen is -2 except-
With Flourine In peroxide compounds where it is -1
e.g. H2O
H= +1 O= -
NH4= N=-3 H=+4
Describe and explain galvanic cells in terms of oxidation/reduction reactions
Galvanic cells are electrochemical cells, they are an arrangement of chemicals and equipment that allows a redox reaction to occur. It physically separates the reductant and oxidant.
Outline the construction of galvanic cells and trace the direction of electron flow
Define the terms anode, cathode, electrode and electrolyte to describe galvanic cells
Electrolyte- a chemical that in a solution or molten form conducts e- Electrodes- a material transferring electrons to and form an electrolyte solution
(graphite and platinum are inert)
Anode- oxidation and negative electrode Cathode- reduction and positive electrode
Gather and present information on the structure and chemistry of a dry cell or lead-acid cell and evaluate it in comparison to one of the following:
runs out. Some can be recharged by forcing the reaction into reverse
do has a large SA and ..
. produces more energy
available to all
Cathode: Ag
Ag2
O + H2O + 2e-
2Ag + 2OH- Elect
rolyte: KOH
Solve problems and analyse information to calculate the potential requirement of named electrochemical processes using tables of standard potentials and half-equations
E o : Standard reduction electrode potential, the tendency of species to gain electrons by comparison to hydrogen
Table of standard Potentials The numbers indicate the tendency of species to be reduced (gain e-). If the
number is negative the species is oxidised (gain e-). The more positive the number the greater the tendency of the reaction to occur
e.g. Cu(s) + 2Ag+
(aq) Cu2+(aq) + 2Ag(s)
The half reactions and their Eovalues are- Cu(s) Cu2+
(aq) + 2e- Eo=0.34 2Ag+
(aq) +2e- Ag(s) Eo=0.80 Total= 0.46
5. Nuclear chemistry provides a range of materials
Distinguish between stable and radioactive isotopes and describe the conditions under which a nucleus is unstable
A unstable isotope is one that emits radiation
An isotope is unstable if: It’s atomic number (z) is greater than 83
It’s ration of neutrons to protons places it outside the zone of satiability
Describe how transuranic elements are produced
Transuranic elements are elements with a greater atomic number (z) than
uranium i.e. >92
To increase the mass number and the atomic number we need to add mass to the original nucleus.
One way of doing this is to add neutrons or possible larger particles such as He nuclei 4
2He
This can be done in two ways:1. With a nuclear reactor where plenty of neutrons are flying about, these
bombard other nuclei2. By accelerating mass, e.g. 4
2He nuclei into other nuclei into other nuclei, this is done in an accelerator called a cyclotron. A cyclotron is useful in the production of nuclei with a short half life Linear accelerators can also be used though they are not as convenient as having an on-site cyclotron at a hospital (they are used to diagnose disease)
Note: the nucleus that is bombarded must not be fissile- meaning it must not be able to split as in a fission reaction.
e.g. 235U will split because it is fissile 238U will not split because it is not fissile
e.g. in a reactor 238U is bombarded with neutrons. Write out the nuclear reaction. Hint- 239
92U is unstable and emits ß particles
23992U + 1
0N 23992U 238
93Np + 0-1e-
Describe how commercial radioisotopes are produced
Many synthetic radioisotopes are made in reactors About 20 of these are useful in medicine and industry Many are made using reactors as a neutron source
Some products of fission: Technium-99 is an isotope used in medical diagnosis It’s preparation is as followed
Uranium- 235
Fission in a reactor
Molybdenum-99 (long-ish half life. This is useful in transportation to a hospital)
Decays continuously to Technetium-99
99Tc is extracted by running a saline solution through the 99Mo
Used in diagnosis
Medical radioisotopes are also produced on-site in cyclotrons i.e. the target substance in bombarded with nuclei Iodine-123 is made in a cyclotron
Identify instruments and processes that can be used to detect radiation Detection of radiation:
Ways to detection include- Photographic film- the film darkens when hit by radiation Cloud chambers- radiation ionises the air and ‘jet streams’ occur Geiger- Müller counter- detects from ionisation (caused by radiation) makes a
pulse which is amplified Scintillation counter- radiation hits particles and causes flashes of light. These
are amplified to make a signal
Identify one use of a named radioisotope: In industry Cobalt-60 In medicine Technetium-99
Describe the way in which the above named industrial and medical radioisotopes are used and explain their use in terms of their properties
Cobalt-60: Industrial radiograph- to inspect metal parts and welds for defects.
Beams of radiation are directed at the object to be checked. More radiation will pass through if there are cracks, breaks, or other flaws in the metal parts and will be recorded on the film.
Properties- Co-60 has a half-life of 5.3 years and can be used in a chemically inert form held
inside a sealed container. This enables the equipment to have a long lifetime and not require regular maintenance.
Technetium-99m: Is used in over half of the current nuclear medicine procedures, such as
pinpointing brain tumours. Properties- It has a very short half-life of 6 hours It emits low energy gamma radiation that minimises damage to tissues but can
still be detected in a person's body by a gamma ray sensitive camera It is quickly eliminated from the body It is reasonably reactive; it can be reacted to form a compound with chemical
properties that leads to concentration in the organ of interest such as the heart, liver, lungs or thyroid.
Process information from secondary sources to describe recent discoveries of elements
In January 2010 scientists successfully formed the new element Ununseptium (z=117)
To creating just 22 milligrams of berkelium took 250 days. To discover Ununseptium two collisions were run, colliding calcium atoms into the berkelium, each taking 70 days. This process created six atoms of Ununseptium.
The Ununseptium lasted only a fraction of a second
Ununseptium is a placer name for element 117, it will change once the element is confirmed.
Use available evidence to analyse benefits and problems associated with the use of radioactive isotopes in identified industries and medicine
Cobalt-60: Benefits- Able to sterilise items that would be damaged by heat-sterilisation
Able to extend the half life of foods that have been damaged in this mannor Has a relitivly long half life so requires little maintenance
Problems- There are radioactive wastes produced during it’s production It is difficult to dispose of spent Co-60
Technetium-99: Benefits- Relatively short half life so leaves the body fairly quickly Emmits low Betta radiation so minimises damage to tissue but is still
detectable by a gamma sensitive camera Problems- High cost Harms living cells Radioactive waste