Tuesday, 9 September 2014

A'level Guide: How to Smash Your A'levels [Part 4: Chemistry]

Alrighto! Chemistry! The subject I have a love-hate relationship with.
Make sure you have the following books in your possession:

1. Chemistry Coursebook by Roger Norris

http://www.preordersbook.com/wp-content/uploads/2013/03/cambridge-international-as-and-a-level-chemistry-coursebook-with-cd-rom-700x700-imadhyapy7zkptgq.jpeg

2. A'level Chemistry Book II by Muhammad Ayub

(The screenshot isn't clear and it's of the Book I for AS level, because I couldnt find any other screenshot on Google. Book II looks similar to this one. It's just purple in colour instead of off-whitish blue)

https://www.xtremepapers.com/community/data/attachments/14/14183-b5f5299bcd90f7094f76c04fa5785ef1.jpg

3. Jim Clark's notes (a.k.a www.chemguide.co.uk)

This here is an amazing website. You should print out the relevant pages, instead of viewing them on a gadget because that is distracting. Jim Clark explains A'level chemistry expertly. All your ambiguities and concepts will become clear if you go through his notes. They're very reader friendly too so you don't get bored.

For each of the following chapters, do go through the AS parts of the chapters that you have studied last year!

➳ Chapter 1: ENERGETICS ✯✯

(Do the entire chapter from M.Ayub)

Okay, so Chemistry starts off easy. It's much easier than the Energetics part we studied in AS level. The Born Haber Cycle is very simple and you just need practice to get it mastered. You must know the equations and definitions of all the standard enthalpies of AS and A-2. Solving the questions and find the Heat of reaction wa sometimes problematic to me. But if you know your maths, and the concept of equations, you'll be fine. Oh, and it's a good move to revise Hess's law. We all hate it, I know. But it'll be helpful.
For refreshing Hess's law from AS level, check this out:  Hess Law Notes by Jim Clark



➳ Chapter 2: ELECTROCHEMISTRY ✯✯

F=Le Calculations
(M.Ayub pg. 27 -29), (Jim Clark's notes: Faraday's Constant , Calculations)
Introduction to Galvanic cell
(Jim Clark's notes: Introduction )
Basic understanding of electrode potientials
(Jim Clark's notes: Basic Definitions in Electrochemistry , Concepts of Electrochemistry )
Standard Electrode potential
(Coursebook pg. 275)
Standard Hydrogen Electrode, Salt Bridge
(M.Ayub pg. 13 - 15)
Feasibility of a reaction
(Jim Clark's notes: Feasibility of a reaction )
Standard Reduction Potiential Values
(Coursebook pg. 279 - 286)
Fuel Cell
(Jim Clark's notes: Fuel Cell )

A pretty basic chapter if read it through thoroughly from Jim Clark's notes. You just have to read them. There's hardly anything you need to learn. It's almost like reading a story. So give it a little time, it will definitely help you, I promise you. Do NOT confuse this chapter with the one we studied back in O'levels 'Electrolysis'. This chapter is about the working of a GALVANIC CELL in which chemical energy is converted to electrical energy in a spontaneous reaction. The O'levels chapter is about the Electrical Conductance in an Electrochemical cell, where electrical energy is converted to chemical energy in a non-spontaneous reaction. In the Galvanic Cell, there is no fixed cathode or anode, but the metal with the more negative standard reduction potential value can be considered as the anode. Remember, if asked to draw (which is not probable) do not miss out the salt bridge. Without the salt bridge, the process can not go on.

➳ Chapter 3: EQUILIBRIA

Concept of pH, Ka, pKa, Kw
(M.Ayub pg. 43 - 47), (Coursebook pg. 301 - 307), (Jim Clark's notes: pH, pKa, Ka , Kw )
Indicators, pH curves
(Coursebook pg. 307 -311), (M.Ayub pg. 53 - 60), (Jim Clark's notes: pH curves , Indicators )
Buffers
(Jim Clark's notes: Buffers )
Solubility product, Common Ion Effect
(M.Ayub pg. 60 - 66), (Coursebook pg. 315 - 319), (Jim Clark's notes: Solubility Product )

I loved this chapter. It was so much fun! Again, focus on Jim Clark's notes and you'll know everything you need to know. You should be known of the difference between pKa and Ka values. Remember, increasing the temperature, increases the value of Ka, but decreases pKa. You should also understand that eventhough Kw also increases with the increase in temperature, water still remains neutral even if it's not at pH 7. Working buffer questions are simple. In A'levels, they tend to complicate Henderson's equation by writing it as pH=pKa-(-log[salt/acid]), but you can simply write this as pH=pKa+(log[salt/acid]). Looks like I didn't do anything, and I didn't really either, but it eliminates the confusion of the negative positive signs. 

➳ Chapter 4: REACTION KINETICS

Rate Equation, Order of Reaction, Rate Constant
(Jim Clark's notes: Orders of Reaction , Reaction Mechanisms ), (Coursebook pg. 328 - 334)
Initial Rate Tables
(Jim Clark's notes: Initial Rate Tables )
Experimental Analysis
(Jim Clark's notes: Experiments ), (M.Ayub pg. 86 - 90), (Coursebook pg. 323 - 327)
Graphs for orders of reactions
(Jim Clark's notes: Curves for Orders of Reactions )
Catalysis
(Coursebook pg. 340 - 343), (Jim Clark's Notes: Catalysis )

This, again, is a very fun chapter. But CIE likes to gives awkward questions on it sometimes. Usually students get confused with the Initial Rate tables, but to be honest, they are the easiest part of this chapter. Careful about those Concentration - time curves though. Learn to recognize how different orders of reactions are plotted.

➳ Chapter 5: TRANSITION ELEMENTS ✯✯✯

Definition, Exceptions, Electroic Configurations
(Coursebook pg. 362)
Properties of Transition Elements
(M.Ayub pg. 129 -130), (Coursebook pg. 364 - 365)
Variable Oxidation States
(Coursebook pg. 363), (M.Ayub pg. 127)
Redox Reactions
(Coursebook pg. 365 - 366), (M.Ayub pg. 135)
Ligands
(M.Ayub pg. 136 - 139), (Coursebook pg. 368 - 369)
Colours of complexes
(M.Ayub pg. 144 - 147), (Coursebook pg. 370 - 371)

I gave this chapter a difficulty of three stars because I personally found the concept of ligands a tad bit complicated. It's not hard. There's just a lot of things going on than what meets the eye. Naming complexes is not required in the CIE syllabus, but you should know the names of the common ligands. You should also know why dx2 and dx2-y2 are at a higher energy level when a ligand approaches (All the five d orbitals are degenerate when there is no ligand present i.e. they are at the same energy level). It's not really mentioned anywhere but when a ligand approaches, it does so on the axis, so dz2 and dx2-dy2 being on the axis are moved to a higher energy state.

  ➳ Chapter 6: GROUP II

Thermal Stability of Nitrates and Carbonates
(Jim Clark's notes: Thermal Stability)
Solubility of Sulphates
(Jim Clark's notes: Solubility of Sulphates )

One of the shortest chapters in Chemistry. All you need to know is the trend of stabilities of Carbonates and Nitrates of Group II elements and the solubility of Sulphates. Everything you need to know is described in detail in Jim Clark's notes, so have a look.


➳ Chapter 7:  GROUP IV ✯✯✯

Variation in melting points and electrical conductivities
(Coursebook pg. 351 - 352), (M.Ayub pg. 110 - 112)
Tetrachlorides; volatilities and thermal stabilities
(Coursebook pg. 352 - 353), (M.Ayub pg. 114 - 115), (Jim Clark's notes: Tetra Chlorides )
Reactivity with water
(Coursebook pg. 353), (Jim Clark's notes: Hydrolysis of tetrachlorides )
Oxides
(Jim Clark's notes: Group IV oxides Don't go too much into the hybridization part. Just skip it!)
Ceramics
(Coursebook pg. 358)
Relative stabilities of oxidation states
(M.Ayub pg. 113), (Coursebook pg. 355 - 357)

I did not like this chapter because you had to learn a lot of stuff and it always got jumbled up! I always confused the stability of +2 and +4 oxidation states. And for some odd reason, I confused Tin with Lead too. I do hope that doesn't happen to you.

➳ Chapter 8: AROMATIC HYDROCARBONS

Bezene shape and bonding, Kekule's structure
(M.Ayub pg. 160 - 161), (Coursebook pg. 374 - 375)
Electrophillic substitution of benzene
(M.Ayub pg. 162 - 164), (Coursebook pg. 376 - 378)
Reactions of Methyl benzene, free radical substitution, oxidation
(M.Ayub pg. 164 -166)
Electrophillic substitution of Methyl Benzene
(M.Ayub pg. 166 - 168), (Coursebook pg. 377)

I didn't quite understand the shape of benzene and the existance of the p-orbitals that created the localized ring on benzene. When I studied FSC and the process of hybridization (which, by the way, is pretty complicated) so that's why I gave this topic two stars. Go through multiple resources apart from the ones i mentioned to reallly understand the shape of Benzene. Search Google and discover it yourself. The reactions of benzene are pretty simple once you've practised writing them down. You must remember the nature of the reagent you're adding, the conditions and catalysts because even if one of those things changes, the reaction changes.

 ➳ Chapter 9: PHENOL


Tri-iodomethane test
(M.Ayub pg. 175 - 178)
Physical and Chemical properties and reactions
(M.Ayub pg. 178 - 180), (Coursebook pg. 379 - 381), (Jim Clark's notes: Phenol Reactions , More Reactions of Phenols)
Acidity of phenol, water and ethanol
(Jim Clark's notes: Acidity of Phenol , Acidity of Ethanol and Water )

Easy chapter. Nothing much to it. You'll understand it in the first study. Just be careful about the reason why Phenol is more reactive than benzene. Jim Clark explains that well. Oh, and remember, Phenol can not react directly with a carboxyllic acid to form an ester. To make an ester using phenol, you need to react it with an Acyl chloride.

 ➳ Chapter 10: CARBOXYLLIC ACIDS AND ACYL COMPOUNDS
✯✯

Introduction to acyl chlorides and their making
(Jim Clark's notes:Preparation of Acyl Chlorides ), (Coursebook pg. 386)
Reactions of Acyl chlorides
(Jim Clark's notes: Reactions with Nitrogen Compunds, Reaction with -OH )
Acidity of Carboxyllic Acids
(Coursebook pg. 384 - 385)
Ease of hydrolysis of Acyl chlorides, Alkyl Chlorides and Aryl Chlorides
(Coursebook pg 386 - 387)
Polyesters
(M.Ayub pg. 195 -196)

We've been reading about Carboxyllic acids for years now, but acyl compounds are a new concept. There is little required on it according to the syllabus but you need to know that they are very reactive so they participate readily in nucleophillic substitution reactions. Acidity trends of organic compounds which you must know are: Carboxyllic Acid > Phenol > Water > Ethanol
Increasing the number of carbon atoms, decreases the acidity. Attaching an electronegative element increases the acidity. You can find more about this in the relevant books.

 ➳ Chapter 11: NITROGEN COMPOUNDS ✯✯

Introduction to amines, physical properties
(Coursebook pg. 390), (Jim Clark's notes: Amines: An Introduction )
Hydrolysis of nitriles
(M.Ayub pg. 201 - 202), (Coursebook pg. 392), ( Jim Clark's notes: Hydrolysis of Nitriles )
Making PhenylAmine
(Jim Clark's notes: Making Aniline )
Basicity of amines
(Coursebook pg. 391)
Reactions of phenylamine
(Jim Clark's notes: Reaction with Bromine water , Reaction with Nitrous Acid )
Coupling Reactions
(Jim Clark's Notes: Coupling Reactions ), (Coursebook pg. 392)
Introduction to amides and their formation
(Jim Clark's notes: Amides , Formation of amides )
Hydrolysis of amides
(Jim Clark's notes: Hydrolysis of amides )
Introduction to amino acids
(Coursebook pg. 394), (Jim Clark's notes: Amino Acids )
Acid-base properties of amino acids
(Coursebook pg. 395), (Jim Clark's notes: Acid-base Behaviour of Amino Acids )
Formation of Proteins
(Coursebook pg. 395)
Hydrolysis of proteins
(Coursebook pg. 396), (Jim Clark's notes: Protein Hydrolysis )

Longest chapter in Organic chemistry and not very simple either, so don't take it lightly. Coupling reactions, although not immensly important, can be quite tricky. You need to learn how Phenylamine is made and it's reactions as well. Another element you must understand is protein/amide hydrolysis. You can carry out hydrolysis in both acidic and alkaline conditions, but both of these yield different products. So don't ever overlook the conditions. Naming of amino acids is not required. However, you should know the more common ones along with their structures like Glycine, Alanine, Aspartic Acid, Glutamic Acid and Lysine.

➳ Chapter 12: POLYMERISATION

Condensation Polymerisation 
(Coursebook pg. 399 - 400), (M.Ayub pg. 224)
Polyamides
(M.Ayub pg. 225 - 226)
Polyesters
(M.Ayub pg. 227), (Coursebook pg. 401)
Techniques
(Coursebook pg. 402 - 404)  
 
  ➳ Chapter 13: [APPLICATIONS] CHEMISTRY OF LIFE

(Do this chapter from any book you please. It's basic stuff you have already studied in Biology so it should be no problem at all. Even the Application Booklet can be used here.)

  ➳ Chapter 14: [APPLICATIONS] MASS SPECTROMETRY ✯✯✯

Working of Mass Spectrometer
(Jim Clark's notes: Working of the Spectrometer, Mass Spectra of elements )
Fragmentation and Molecular Ions with their Peaks
(Coursebook pg. 468 - 470), (Jim Clark's notes: Fragmentation , M+ Peak , M+1 Peak , M+2 Peak )

Applications in Chemistry is a long section; much longer than in either Physics or Biology. It looks very hard in the beginning. But it's all concepts, practive and techniques. Nail it, and you'll see how fun Applications is. Mass Spectrometry just requires a wide awake mind. Yes, The peaks can be confusing, but just go through Jim Clark's notes. He explains it awesomely. Do NOT confuse the mass spectra of elements (which we have been reading for years now) with the mass mspectra of organic compounds (which you are studying now). Compounds produce fragmentation so many peaks are seen on the graph. Elements do not.

 ➳ Chapter 15: [APPLICATIONS] CHROMATOGRAPHY ✯✯✯

Thin Layer Chromatography
(M.Ayub pg. 312), (Jim Clark's notes: TLC ), (Coursebook pg. 464 -465)
High Performance Liquid Chromatography
(Coursebook pg. 465), ( Jim Clark's notes: HPLC )\
Gas liquid Chromatography
(Jim Clark's notes: GLC ), (Coursebook pg. 466 -467), (M.Ayub pg. 319 - 320)
Paper Chromatography
(Coursebook pg. 461 - 462), (Jim Clark's notes: Paper Chromatography )
PCBs
(Coursebook pg. 472 - 473) 
Solvent Extraction
(M.Ayub pg. 306 - 311), (Jim Clark's notes: Partition Co-efficients  )

Chromatography, in my opinion is the hardest chapter in applications, mainly due to HPLC and GLC. There's a lot of information that gets jumbled up that you must learn. Especially about the different phases of the components. So, careful about that. Take this chapter slowly, in bits, or you'll end up going insane!

  ➳ Chapter 16: [APPLICATIONS] NUCLEAR MAGNETIC RESONANCE ✯✯✯

Spin States, General description of NMR, TMS, Chemical Shift
(Coursebook pg. 452 - 453), ( Jim Clark's notes: Background of NMR)
Techniques & Concepts
(Coursebook pg. 455 - 458), (Jim Clark's notes:  Low Resolution NMR , High Resoultion NMR)

Most people found this a very hard chapter, especially when solving the questions, which is why I gave it 4 stars. But personally, it isn't so hard. Once you understand a basic high resolution NMR spectrum perfectly, you can solve any question easily. Read, and re-read Jim CLark's notes over and over again and solve multiple past paper questions. For NMR, there is no shortcut - You MUST practice NMR questions a lot to get them mastered.

➳ Chapter 17: [APPLICATIONS] X-RAY CRYSTALLOGRAPHY

Techniques
(Coursebook pg. 460 - 461), (Jim Clark's notes: X-ray Crystallography)

Nothing to this chapter. It's short and to the point. Just a side information, Crystals are used for Xray Diffraction because they have a wavelength comparable to that of X-rays.


➳ Chapter 18: [APPLICATIONS] ELECTROPHORESIS ✯✯

Definition and uses
(Coursebook pg. 447)
Concepts and techniques
(Jim Clark's notes: Electrophoresis working ), (Coursebook pg. 448)
 DNA Fingerprinting
(M.Ayub pg. 290)

If you've done Biology, you should already know the basic principle behind Electrophoresis. The Chemistry syllabus requires mostly just the working of Electrophoresis, but you can be asked in you Paper 5 about how to set the experiment up, so do not overlook that!
  
  ➳ Chapter 19: [APPLICATIONS] DESIGN AND MATERIAL

Designing drugs
(Jim Clark's notes: Drug Design )
Drug Delivery
(Jim Clark's notes: Drug Delivery )
Polymerization
(Jim Clark's notes: Polymerization, Side Chains )
Nanotechnology
(Jim Clark's notes: Nanotechnology )
Environmental Chemistry
(Jim Clark's notes: Environmental Chemistry )
Recycling and Efficiency
(Jim Clark's notes: Green Chemistry )

This is a very general topic. Initially it looks as if there's a lot to learn, but there isn't. You don't need to cram everything. Just go through the above links once and get them into your knowledge. Questions asked on this chapter require background knowledge and common sense.
muirrereveed to
Chemistry, in my opinion, is the hardest out of all the other subjects in A-2, so keep your eyes peeled when you study it!

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