criticise my syllabus summary! (1 Viewer)

[.ben]

hi, this is a syllabus point by point summary for the first few points. i just want to know i there is anyway to improve it (e.g. reword things, or offer more for some points etc) thanks!
---------------------------------------------------------------------------


 Identify the industrial source of ethylene from the cracking of some of the fractions from the refining of petroleum

Fractional distillation is a process by which hydrocarbons are separated through different boiling points into fractions. Two fractions in particular, known as the naptha and LPG (liquefied petroleum gas), are used to manufacture C2H4 ethylene (ethene).

The general term for the process used to produce ethylene is cracking. Cracking is the breakdown of longer chain (C>20) hydrocarbons into shorter and more useful hydrocarbons. There are two types of cracking, thermal (steam) and catalytic cracking.

Thermal cracking involves high temperatures (450oC to 750 oC) and pressures (up to 70 atmospheres) without the presence of a catalyst. Products obtained from this process are mainly unsaturated hydrocarbons – this is because the carbon-carbon bonds break resulting in the formation of free radicals leading to various products. For this reason, thermal cracking is favoured over catalytic cracking.

Catalytic cracking, on the other hand, uses low temperatures (approximately 500oC) and low pressures with a zeolite (sodium aluminosilicate) catalyst which lower the activation energy required for reactions to take place hence the lower temperatures and pressures. Because of this, catalytic cracking is a more energy friendly process than thermal cracking.

 Identify that ethylene, because of the high reactivity of its double bond, is readily transformed into many useful products

Because ethene is an alkene, it possesses a double bond which is the centre of its high reactivity. This double bond presents an area of high electron density attracting many electronegative elements which, when broken, allows ethene to be transformed into many useful products.

 Identify that ethylene serves as a monomer from which polymers are made

Monomers are small molecules such as ethene which are able to join together to form polymer macromolecules such as polyethylene. Being a monomer, ethylene acts as the basis for many polymer products such as polyethylene.

 Identify polyethylene as an addition polymer and explain the meaning of this term

The general term for the process of joining together monomers to make polymers is polymerisation. In the specific case of polyethylene, this process is addition polymerisation. Addition polymerisation occurs when monomer units simply add to each other forming a long chain known as a polymer. It works because when the double or triple bond [of a monomer] breaks, it frees up electrons which can then bond to create long chains.

n(CH2=CH2) * -(CH2 – CH2)-n

There are no by products of addition polymerisation.




 Outline the steps in the production of polyethylene as an example of a commercially and industrially important polymer

Polyethylene is generally produced in 3 steps with varying production conditions, monomers and catalysts yielding polymers with different properties and thus different uses.

The 3 steps are initiation, propagation and termination.

Initiation involves the combining of the ethylene monomer and an initiator molecule such as an organic peroxide. At high temperatures and pressures, the initiator molecule decomposes into free radicals which saturate the ethene monomers

Propagation is the process where activated or radicalised monomer units repeatedly react with each other to create long continuous chains.

Termination, the final process, occurs when the desired molecular weight is achieved. The free radicals react with themselves to form hydrocarbon molecules which are recycled back into the cracker.

 Identify the following as commercially significant monomers: - vinyl chloride – styrene by both their systematic and common names

Two commercially significant monomers include vinyl chloride – common name (chloroethene – systematic name) and vinyl benzene – common name (styrene – systematic name). Their structures are detailed below.

 

[pLuvia]

 Identify that ethylene, because of the high reactivity of its double bond, is readily transformed into many useful products

What I added was the different Addition reactions you could have with ethylene i.e
Hydration (addition of water)
Hydrogenation (addition of hydrogen gas)
Halogenation (addition of halogens)
Hydrohalogenation (addition of HCl, HF, HI, HBr)

 Identify polyethylene as an addition polymer and explain the meaning of this term

Polyethylene is an addition polymer because it is formed by molecules adding together without losing atoms

 Outline the steps in the production of polyethylene as an example of a commercially and industrially important polymer

I'm not sure if this is necessary, but I talked about the old Gas phase process which produces LDPE which are non-crystalline and the Ziegler-Natta process which produces HDPE which are crystalline

 

[Riviet]

 Identify that ethylene, because of the high reactivity of its double bond, is readily transformed into many useful products

You need to give at least 2 examples of useful products such as polyethylene, which is a polymer formed from ethylene.

For most other dotpoints, you might want to go into a little more detail, even though they're "identify" dot points. The reason for this is because alot of these smaller dotpoints are incorporated into mini essays, worth 5, 6 or even 7 marks, and that is where your detailed summaries become handy.

 

[Dreamerish*~]

I'm not sure if this is necessary, but I talked about the old Gas phase process which produces LDPE which are non-crystalline and the Ziegler-Natta process which produces HDPE which are crystalline

The Ziegler-Natta process is not necessary. For this dot-point, the main information you need to know is the three steps in the production of LDPE - initiation, propagation and termination.

Ben, remember to always give examples, and it is important to know the properties and uses (and interrelate them) of polyvinylchloride and polystyrene.

 

[pLuvia]

Ok thank for that advice Dreamerish*~

For most other dotpoints, you might want to go into a little more detail, even though they're "identify" dot points. The reason for this is because alot of these smaller dotpoints are incorporated into mini essays, worth 5, 6 or even 7 marks, and that is where your detailed summaries become handy.

Good point Brian

 

[xvelidras]

vinyl benzene – common name (styrene – systematic name). Their structures are detailed below.

First of all, corrections:
Common name: styrene
Systematic name: ethenylbenzene/phenylethene

your preference, personally, i chose phenylethene =P

'attracting many electronegative elements'
I don't think you would have been taught that, and any book utilising that phrase should be burnt! But first of all, i commend you, because many fail to mention that point. The word your looking for it ELECTROPHILES. "electron loving species"
WHY?! because those which attack your double bond to cause a reaction to occur and alter ethylene mostly are NOT elements.

Well anyway, that dot point and the addition polymer dot point were the only one's i have any comment on. pLuvia's uberly succinct answer is wonderful. Though you may still want to add that part about opening of a double bond.

Wrote my version of 'Identify that ethylene, because of the high reactivity of its double bond, is readily transformed into many useful products' Feel free to use, reject or criticise.

Ethylene's double bond imbues it with high reactivity because it is a site of higher electron density. Hence it is prone to attack by electrophiles. Reaction with these electrophiles breaks the double bond of ethylene and transforms it into other useful products such as ... (whatever examples you want to use)

 

[pLuvia]

Hey sorry .ben for bombarding into your thread but I didn't want to create a new thread and as this is thread about syllabus dot points I'll ask here

For this dot points

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

What does it mean by assess the potential of ethanol as an alternative fuel? What am I meant to say for this bit?

 

[bananasmoothy]

Hey sorry .ben for bombarding into your thread but I didn't want to create a new thread and as this is thread about syllabus dot points I'll ask here

For this dot points

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

What does it mean by assess the potential of ethanol as an alternative fuel? What am I meant to say for this bit?

Assess (give a judgement or something) the potential of ethanol as an alternative fuel (is it any good as an alternative to other, present fuels).
Mmmm did this middle of term 4, brain is sleepy and chem book is too far away, but there's something about it being renewable and fossil fuels not (duh). Yeah.

Anyway, is it any good as a fuel compared to what is currently available? Advantages and disadvantages I'm sure you understand.

 

[angelxtearz]

for the catalytic cracking, isn't that only to decompose high molecular weight hydrocarbons (15-25 C atoms) ????
do we really have to know the temperatures required, i kno thts a blonde q but meh.

 

[pLuvia]

Catalytic cracking breaks alkanes between C15 - C25 into one alkane and one alkene

eg C₁₅H₃₂ --> C₁₀H₂₂ + C₅H₁₀

 

[mitsui]

pluvia. for the question u asked
our teacher told us to do research on newspapers to find the most current criticism and approval against the alternative use of the ethanol

basically, wat u have to do is list out all the adv. vs. disadv and give ur judgement on that (be sure to inclu the economical factors too)

a random note:using ethanol as an alt. fuel is good because it is the same cost as fossil fuels, and are much easier to obtain (from sugar canes). the problem wif using ethanol to replace fossil fuels however, is the lack of land for growing the amount of sugar canes needed.

<someone correct me if i am wrong. thx>

 

[.ben]

hey thanks guys for the feedback ill post another one tomorrow implementing ur suggestions.

 

[mitsui]

Hydration (addition of water)
Hydrogenation (addition of hydrogen gas)
Halogenation (addition of halogens)
Hydrohalogenation (addition of HCl, HF, HI, HBr)

is it neccessary to remmebr the above terms??all i haf are
ethene wif water to form ethanol (disinfectant)
ethene wif oxygen to form ethlyene oxide (sterilliser)
plothylene for plastic
ethanoic acid

??

 

[pLuvia]

a random note:using ethanol as an alt. fuel is good because it is the same cost as fossil fuels, and are much easier to obtain (from sugar canes). the problem wif using ethanol to replace fossil fuels however, is the lack of land for growing the amount of sugar canes needed.

I have to disagree with you there Jing. Although it is environmentally friendly, renewable resource and all that. It requires energy from oil, coal etc to make the fertilisers and for distillating the ethanol into pure ethanol, which economically will cost more than just using oil.

 

[mitsui]

yea i know that it
but i recalled my teacher saying that using ethanol is economically cheaper to use as compare to fossil fuels.

i will check up on that. x]

 

[pLuvia]

Not that hard to remember lol

hydration (think of water)
halogenation (think of halogens)
hydrohalogenation (hydrogen and halogen)
hydrogenation (hydrogen)

The only hard thing I think is hydration and dehydration (opposite) use concentrated sulfuric acid or phosphoric acid and dilute sulfuric acid respectively. And hydrogenation needs a catalyst of either N, Pt, Pd

 

[mitsui]

lol true

 

[beabenn]

The Ziegler-Natta process is not necessary. For this dot-point, the main information you need to know is the three steps in the production of LDPE - initiation, propagation and termination.
[.[/SIZE]

I disagree...if this was a 4-5 mark question, 1-2 marks could be allocated for an outline (main features/definitions) of the Zeigler-Natta process. Just remember, write as muchas you can without repeating yourself

 

[Riviet]

beabenn has made a good point. If the question wants more detail, you are likely to need to make reference to the Zeigler-Natta process used for the production of HDPE in addition to the steps used to make LDPE, depending on what you are asked to write about.

 

[.ben]

ok guy, i edited a bit and added a bit more. tell me what you think. thnaks.

---------------------------------------------------------------------------

 Identify the industrial source of ethylene from the cracking of some of the fractions from the refining of petroleum

Fractional distillation is a process by which hydrocarbons are separated through different boiling points into fractions. Two fractions in particular, known as the naptha and LPG (liquefied petroleum gas), are used to manufacture C2H4 ethylene (ethene).

The general term for the process used to produce ethylene is cracking. Cracking is the breakdown of longer chain (C15-100) hydrocarbons into shorter and more useful hydrocarbons. There are two types of cracking, thermal (steam) and catalytic cracking.

Thermal cracking involves high temperatures (450oC to 750 oC) and pressures (up to 70 atmospheres) without the presence of a catalyst. Products obtained from this process are mainly unsaturated hydrocarbons – this is because the carbon-carbon bonds break resulting in the formation of free radicals leading to various products. For this reason, thermal cracking is favoured over catalytic cracking.

Catalytic cracking, on the other hand, uses low temperatures (approximately 500oC) and low pressures with a zeolite (sodium aluminosilicate) catalyst which lower the activation energy required for reactions to take place hence the lower temperatures and pressures. Because of this, catalytic cracking is a more energy friendly process than thermal cracking.

 Identify that ethylene, because of the high reactivity of its double bond, is readily transformed into many useful products

Because ethene is an alkene, it possesses a double bond which is the centre of its high reactivity. This double bond presents an area of high electron density which, when broken, allows ethene to be transformed into many useful products. Because of this ethene attracts many electrophilic species.

There are two main types of reactions associated with ethene, addition and polymerisation.

Examples of addition reactions possible for ethene include:

A hydration reaction occurs when water adds across the double bond of ethene resulting in the production of ethanol.

CH2CH2 + H2O * CH3CH2OH

A halogenation reaction occurs when bromine, a coloured element is added across the double bond of ethene resulting in the formation of 1, 2, - dibromoethane which is colourless.

CH2CH2 + Br2 * CH2BrCH2Br

A hydrohalogenation reaction involves the use of hydrochloric acid reacting with ethene to form chloroethane

CH2CH2 + HCl * CH2HCH2Cl



A hydrogenation reaction involves the conversion of ethene into ethane by the addition of hydrogen gas.

CH2CH2 + H2 * CH3CH3

 Identify that ethylene serves as a monomer from which polymers are made

Monomers are small molecules such as ethene which are able to join together to form polymer macromolecules such as polyethylene. Being a monomer, ethylene acts as the basis for many polymer products such as polyethylene.

 Identify polyethylene as an addition polymer and explain the meaning of this term

The general term for the process of joining together monomers (without the loss of any atoms) to make polymers is polymerisation. In the specific case of polyethylene, this process is addition polymerisation. Addition polymerisation occurs when monomer units simply add to each other forming a long chain known as a polymer. It works because when the double or triple bond [of a monomer] breaks, electrons are freed up which can then bond to create long chains.

n(CH2=CH2) * -(CH2 – CH2)-n

There are no by products of addition polymerisation.

 Outline the steps in the production of polyethylene as an example of a commercially and industrially important polymer

Polyethylene is generally produced in 3 steps with varying production conditions, monomers and catalysts yielding polymers with different properties and thus different uses.

The 3 steps are initiation, propagation and termination.

Initiation involves the combining of the ethylene monomer and an initiator molecule such as an organic peroxide. At high temperatures and pressures, the initiator molecule decomposes into free radicals which saturate the ethene monomers

Propagation is the process where activated or radicalised monomer units repeatedly react with each other to create long continuous chains.

Termination, the final process, occurs when the desired molecular weight is achieved. The free radicals react with themselves to form hydrocarbon molecules which are recycled back into the cracker.

 Identify the following as commercially significant monomers: - vinyl chloride – styrene by both their systematic and common names

Two commercially significant monomers include vinyl chloride – common name (chloroethene – systematic name) and styrene – common name (phenylbenzene – systematic name). Their structures are detailed below.

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

Polystyrene is stable, rigid, highly amorphous/transparent, and easily expanded; therefore it can be used for food containers, switches, CD cases, cups and insulation

Polyvinylchloride (PVC) is very strong (dipole-dipole attractions), resists water and retards its own combustion with the release of chlorine. It can be used for water pipes, siding, floor coverings, credit cards, raincoats and shower curtains.


Students:
 Identify data, plan and perform a first-hand investigation to compare the reactivities of appropriate alkenes with the corresponding alkanes in bromine water

 Analyse information from secondary sources such as computer simulations, molecular model kits or multimedia resources to model the polymerisation process


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

Students learn to:
 Discuss the need for alternative sources of the compounds presently obtained from the petrochemical industry

Due to longevity and environmental issues, there exists a need for alternative sources of energy currently obtained from the petrochemical industry.

Currently, many polymer products are derived from fossil fuels which are a non-renewable resource. Despite the fact that the petrochemical industry only uses 5% of the total oil used globally, there is a general consensus in the world community that fossil fuels will eventually be exhausted thus placing great pressure on scientists to develop alternative sources of raw materials used in the petrochemical industry. In recent decades attempts have been made to resolve this problem; however none have been economically viable enough to replace fossil fuels. But, as shortages of fossil fuels become more apparent, alternative products such as biopolymers may become a feasible option.

Environmental damage caused by the non-degradability of current polymers also calls for ‘cleaner’ alternatives. Added to this is the issue of pollutants released from factories burning fossil fuels thus adding to the greenhouse effect and global warming. Continuing use of fossil fuels presents a danger to all living organisms.

 Explain what is meant by a condensation polymer

Condensation polymers are polymers created by the process of condensation polymerisation.

 Describe the reaction involved when a condensation polymer is formed

Condensation polymerisation involves a reaction between two different monomer units (sometimes called copolymers) where each monomer has two identical functional groups. The formation of a polymer chain occurs when the two functional groups of the monomer units join and a small molecule; in this case water is ejected. Repetition of this mechanism ensures long and linear polymer chains. Examples are given below.

 Describe the structure of cellulose and identify it as an example of a condensation polymer found as a major component of biomass

Biomass is any organic material produced by the photosynthetic conversion of light energy to chemical energy.

Cellulose is a condensation polymer formed from glucose and comes under the general category of starches which are polymers of glucose. An equation representing the formation of cellulose is shown below.







There are two types of glucose, α-glucose and β-glucose. While starch consists mainly of α-glucose, cellulose is formed wholly of β-glucose.


As a component of biomass, cellulose represents approximately 75%, thereby satisfying it as a major component.