chemistry – production of materials notes 1. fossil fuels ... – production of materials notes...

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

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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









Identify the following as commercially significant monomers:

Vinyl Chloride by both their systematic and common namesVinyl Chloride/ chloroethene, is the monomer from which polyvinyl Chloride (PVC) is made.

Styrene by both their systematic and common namesStyrene is the monomer from which Polystyrene is made.

Describe the uses of the polymers made from the above monomers in terms of their properties

Vinyl Chloride/ chloroethene:glue and pipes

Styrene: cups and plates

2. Some scientists research the extraction of materials from biomass to reduce our dependence on fossil fuels

Discuss the need for alternative sources of the compounds presently obtained from the petrochemical industry

Petrochemical industry: industry that produces/uses petroleum as a raw material









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

Biomass: material produced by living organisms









Cellulose is a major component of biomass

Monomer- glucose Polymer- cellulose

When glucose monomers join to form cellulose they also form water. This makes cellulose a condensation polymer.

The glucose monomers are linked in strong covalent bonds, there are also hydrogen bonds, so cellulose is: Linear Rigid

Strong Chemically stable

Identify that cellulose contains the basic carbon-chain structures needed to build petrochemicals and discuss its potential as a raw material

Cellulose could be used to make some chemicals we currently get from crude oil

There are large amounts of cellulose left over from agricultural processes. These are usually burnt, berried or composted.

Cellulose Glucose Enzymes called cellulase break down the microscopic structure of

cellulose

Glucose Ethanol This is done by yeast, in a process known as fermentation

Ethanol Ethylene Fermentation can be heated in the absence of oxygen to form

ethylene and water

Advantage Cellulose can be obtained from structures that are currently thrown away,

and are difficult to dispose of Cellulose is a renewable resource

Disadvantages Much of the energy is required for this process comes from oil, using more oil

than would be used to crack oil to ethylene More expensive Ethical problems- using crops to make plastics while people are starving









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)









Yeast acts as a catalyst Glucose is ground up with water in an aqueous form C. 37 o C C6H12O6(aq) 2C2H6O +2CO2

Glucose ethanol(15%) + Carbon dioxide

Define the molar heat of combustion of a compound and calculate the value for ethanol from first-hand data

Molar heat of combustion- the energy released when 1 mol of a substance undergoes complete combustion in a plentiful supply of oxygen

ΔH=-mc Δ T ΔH- change in heat (Joules) m- the mass of water that is heated (g) c- heat capacity of water (4.18JK-1g-1

ΔT- change in temperature

To then find the molar heat of combustion- = Δ H n

Or to find the amount of Kj/g- = Δ H g (of the water heated????)

Assess the potential of ethanol as an alternative fuel and discuss the advantages and disadvantages of its use

Advantages Disadvantages

Renewable Large amounts of arable land

Makes sugar production more viable

Does not produce as much energy as octane

Less likely to undergo incomplete combustion so less CO emissions

Corrodes car engines if used with more than 10% ethanol

Extend supply of petrol High cost of distillation

Does not add to the Carbon cycle

Identify the IUPAC nomenclature for straight-chained alkanols from C1 to C8









1 Meth

2 Eth

3 Prop

4 But

5 Pent

6 Hex

7 Hept

8 Oct

Process information from secondary sources to summarise the processes involved in the industrial production of ethanol from sugar cane

Process information from secondary sources to summarise the use of ethanol as an alternative car fuel, evaluating the success of current usage

Today: 10% of Brazils total energy usage is provided by ethanol In Australia ethanol is mixed with petrol (usually no more than 10%)

Present information from secondary sources by writing a balanced equation for the fermentation of glucose to ethanol

C6H12O6(aq) 2C2H6O +2CO2

Glucose ethanol(15%) + Carbon dioxide

4. Oxidation-reduction reactions are increasingly important as a source of energy

Explain the displacement of metals from solution in terms of transfer of electrons

More active metals displace less active metals in a solution.

The more active metal looses electrons (oxidation) The least active metal gains electrons (reduction)

For example: If an iron nail is placed in a solution of blue copper (II) salt, some of the iron

nails dissolves.









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:

Type

Chemistry

Uses Notes

Cost and

practicality

Impact on

society

Impact on

environment









Dry cell

Anode: Zn

ZnZn2++2e-

Torch batteries

Radios Calculat

ors

Once the materials are used up they stop working

Cheap, small, reliable, easy to use, portable,

1.5V no matter what size they are

No negative impact

No pollution issue

Zn and Mn are both used by plants

Cathode: Carbon rod embedded in paste

2MnO2 + 2NH4

2+ + 2e-

Mn2O3

+ 2NH3 + H2O

Electrolyte: MnO2, ZnCl2, NH4

Cl, water paste

Button Cell

Anode: Zn

Zn + 2OH-

ZnO + H2O + 2e-

Cameras

Heart pacemakers

Hearing aid

The battery ‘dies’ when the Zn

Ag2O is expensive,

ZnO is in powder form

Hearing aids and pacemakers can be small and compact

Expensive, so not

No negative affect









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









e.g. Cobalt-59 is used to make Cobalt-60 59

27Co + 10n 60

27Co

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









chemistry – production of materials notes 1. fossil fuels ... – production of materials notes...

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