Edexcel Chemistry A-level Revision Guides

I have now completed the A-level revision guides for the Edexcel Chemistry A-level to complete the set with AQA and OCR. Make sure you go to the correct menu.  These are the first draft for the Edexcel so comments are welcome. I did used to teach Nuffield Chemistry which a lot of this course is based on so much seemed familiar to me.

Revision Time

I had a message asking if I was going to give any revision advice and hints about what will be good to learn. I suspect the person was hoping I would have a clairvoyant ability to know what will be in the exam. I am sorry to say I don’t. I will, however, give some general advice about revision.

1. Start now

2. Read, understand and sort your revision notes out first. Understanding is the key to doing well. There are always students who try to succeed at A-level by learning by heart the answer to every past question but don’t understand it. That is not going to get you a high grade. You will meet lots of questions that will involve applying your understanding.

My notes on here were written as memory aids for my students who I had assumed had understood the main concepts in their lessons. So if you read something on my revision notes you don’t understand, you should go back to your lesson work, textbook, teacher for help. I can also recommend  http://www.chemguide.co.uk for good explanations.

3. Look at past papers. All the major exam boards have them on their websites. Don’t try to do them as mock exams at the start. Use them to get familiar with the sorts of questions that get asked. When you find questions you can’t do, go back to your notes and try to work out what might be wrong. Are you missing ideas/ facts from your notes? Do you need more explanation?

4. When you are happy with the big concepts start concentrating on finer detail. Make sure you are using the correct definitions- these can vary between exam boards. Do your explanations for things like le Chatelier, reaction rates and ionisation energies have the right detail in them? These tend to be areas people understand but lose valuable marks through sloppy explanations. Do your curly arrows in mechanisms start and end in the right place? The list goes on as there is lots of fine detail and it is crucial you know it. In my experience it is often the fine detail that makes the difference at AS between A and C grades rather than major problems in understanding.

5. Don’t cut corners in your revision. You need to expect questions on everything in the syllabus.

OCR Chemistry A-level Revision Guides

You will find a new page with OCR A-level Chemistry A revision guides. They are based on my original AQA guides but are completely rearranged to follow the OCR module structure. I have reviewed all content to make sure it is consistent with OCR syllabus and past papers, so there have been lots of things removed and quite a few things added. I’m not claiming they are perfect so am happy for comments for improvements etc.

Faulty A-level bonding explanations

I tried these examples with my classes this year. They are all mistakes I have seen students make in exams. Some of them are obviously wrong and others are more subtly wrong.

So can you work out what is wrong with the following explanations?

  1. Calcium has a higher melting point than Barium because there are stronger intermolecular forces between its atoms
  2. PH3 has covalent bonding because phosphorus has a small electronegativity
  3. Methane has a low boiling point because it has weak van der waals between its atoms
  4. Ammonia (NH3) has a trigonal planar shape because it has 3 bond pairs trying to get as far as way as possible from each other
  5. A metallic bond in an element is the electrostatic force of attraction between its nucleus and its delocalised electrons
  6. CH4 has a tetrahedral shape as the four hydrogen atoms try to repel as far away from each other as possible
  7. Water has a higher boiling point than H­2S because it can form hydrogen bonds between its O and H atoms
  8. NaF has a higher melting point than NaBr as fluorine is a smaller atom and so has stronger bonding between its atoms
  9. CO2 is a gas because it has weak covalent bonds
  10. CCl4 is a non-polar molecule because there is no electronegativity difference between C and Cl
  11. NaCl can dissolve in water because it can hydrogen bond with water
  12. Sodium chloride can conduct electricity when molten because it has free electrons.

Ether

I was going through a pupil’s A-level papers recently trying to find one extra mark so she could get the A* she was one mark away from.  There was one question asking for reagents and conditions to convert a nitrile to an amine. One possible answer was using LiAlH4 dissolved in ether. The pupil had written LiAlH4 but not put ether. I had not seen this condition required before – although looking through past papers it had come up before in Jan 2004. So why is it important we use ether here and what is it? There is no other mention of it on the syllabus.

Ether is the common name for Ethoxyethane (also known as diethyl ether). Its formula is CH3CH2OCH2CH3, and it contains the ether functional group (-C-O-C-). Ether is a highly volatile liquid that can be used as a solvent but is dangerously flammable. What does volatile mean in chemistry and why does increasing volatility of organic substances mean they are more flammable?It has a lower boiling point than ethanol even though it is a larger molecule. Can you explain why? (Think about hydrogen bonding). 

LiAlH4 is a reducing agent that can be used to convert carboxylic acids to alcohols, amides to amines and nitriles to amines (only the last reaction is required for the syllabus). The choice of solvent for LiAlH4 is important because it can react with some solvents. It reacts with the common solvents of water and ethanol in a similar way producing a gas. What bond in the water and ethanol must be broken by the LiAlH4 ? What gas do you think it would form? Why would Ether not react with the LiAlH4 in this way?

NaBH4 is another reducing agent we have met (used to convert carbonyls to alcohols). This is a less strong reducing agent and does not react with water and ethanol, so these can be used as a solvent for NaBH4 instead of ether.

Ether has had more uses than just as a solvent. It has anaesthetic properties and was one of the first general anaesthetics used in the 19th century. It is no longer used because it is too flammable and can cause nausea in the patient. It has also some history as a recreational drug. Hunter S Thompson in the cult novel ‘Fear and Loathing in Las Vegas’ makes a few references to it.  This is the main advantage of ether: it makes you behave like the village drunkard in some early Irish novel…total loss of all basic motor skills: Blurred vision, no balance, numb tongue-severance of all connection between the body and the brain. Which is interesting, because the brain continues to function more or less normally…you can actually watch yourself behaving in the terrible way, but you can’t control it.” Before you start thinking that sounds fun, ether will apparently attack your stomach lining if you drink it.

Fortunately we found the student the one mark she needed elsewhere on the paper and on getting it remarked by the exam board she gained her A*. 

Advice for new L6 Chemists

Welcome new chemists whether at Bancroft’s or elsewhere to your new A-level course. Just a little bit of advice to start you off. I shall not try to describe what a perfect pupil is and hope you all become one, but there are a couple of attributes you should all try to take note of.

  1.  When you come across a question you can’t do off the top of your head, don’t give up and leave it blank. Try to find the answer out! Look in the text book, the revision guides and powerpoint notes on here, Google it, ask for help- anything that works. Questions at the start of the A-level are not going to be that hard to find the answer for.
  2. Ask for help when you need it. In my experience over the years, it is generally the best students who ask the most questions. I often find it is the pupil destined for Oxbridge that will be tracking me down with a little list of points they would like some clarification on.

I will post some more specific chemistry advice as we go through the year.

Good luck and enjoy. It’s a great subject

All the revision guides are now posted. I have posted the powerpoints as pdf notes as these work better opening on ipads/iphones although this has meant the animations are not there.

Welcome to my new site. This site mainly exists to host my revision guides that I have written for the AQA A-level chemistry course. I started compiling them 5 years ago for my pupils as I was getting annoyed at spending lots of money on buying new exam board sponsored materials every time they updated the syllabus. I have updated them many times to make sure they are up to date with current exam questions and approaches. Some earlier versions of my revision guides have been circulating on the net for a couple of years on ‘thestudentroom’. I wanted to post here the most recent versions. They may be useful for other A-level courses but they are written very much for the AQA course. I will also be posting some of my powerpoints that I wrote before the revision guides. I have been busy this summer updating them and replacing pictures I got from the net with my own versions. These could be useful to both teachers and students. The powerpoints tend to go into more detail than the revision guides and are less tied to the syllabus as I started writing them when I taught Nuffield Chemistry. I will also blog from time to time about teaching/learning of Chemistry