How do you do it?

Personally, I find section 9.2 one of the hardest parts of the course to teach. It relates to voltaic cells. I can never remember is it left minus right or vice versa, which side is positive, which is negative? In order to help teach this I put together a useful set of ideas / principles that I now use to help my teaching. It does involve some learning / memorization of facts but once these points are learnt, everything else ...

Redox Cells: Revision Checklist

When I teach about redox cells, I like starting with the Daniell cell. It is an example of the world’s first battery (cell) and if you remember the details of it, you can apply to same rules to any unfamiliar redox cells. First, a diagram of the cell itself: Hazmat2, via Wikimedia Commons (CC BY 3.0) Note that the zinc half cell is on the left and the copper half-cell on the right. This is important to remember when it comes to ...

The Halogens and the Sea

There are a few references to lab work in this post – I do need to stress that any labs you carry out need to be under the supervision of one of your teachers (and risk assessed by the teacher) and carried out in school. I have always been fascinated by the link with the number of substances dissolved in the sea. For example, gold ions are dissolved in the sea and it is estimated that there are getting on for ...

Potassium Production (2)

The previous blog post dealt with the amount of potassium produced annually. As promised, this posting delas with the industrail method behind its production. Essentially, there are three methods open to the chemist. 1, Electrolysis of potassium hydroxide (as developed by Davy who first isolated the metal). This is not very practical for a whole variety of reasons - why? 2, Industrially, by the 'Thermal method'. Here, Potassium Chloride is reacted with Sodium in a displacement or redox reaction: KCl + Na --> K + ...

Top Tips for Success (3)

Read the question - it may seem like an obvious thing to say but make sure you do this. Think! What is the question asking me. A question that English speakers (if you are taking your exam in English) seem to get wrong is along the lines of: Cl2 + 2Br- --> 2Cl- + Br2 What is the oxidising agent? English speakers see the word 'oxidising' and immediately think oxidation. The substance being oxidised is Br- and they write this as their answer - but ...

Oxidation States of Vanadium

Here is a great lab to use, whether it with regards to redox (topic 9) or transition metals (topic 13): Vanadium It deals with looking at the oxidation states of vanadium by reducing it with Zinc and the re-oxidising it with MnO4-. There is lots of good teaching to get over in this lab, from understanding redox and writing half equations to seeing that transition metals can have variable oxidation states through the colour of their ions. Please note, as with any lab outlined ...

Happy New Year

Happy New Year to everyone - wherever you are! I hope that it was an enjoyable rest for you. Here in the UK Christmas really does feel over and done with. School has started and the holiday seems a long way away. Last night we took down our Christmas tree and realised that we still had a large number of uneaten candy canes. This posed me with a dilemma..... .... give the children even more sugary sweet substances (as if they haven't ...

Geobacter – a natural battery?

Geobacter are a remarkeable group of bacteria. I first read about them in a BBC news article about bacteria that were able to remove Uranium for contaminated water (click here for the article). But after some research they seem even more amazing as ... ... they can also be used to clean up spilt petroleum. What makes them remarkable is that they produce a series of nanowire that connects them to the substance being reacted. They substance is broken down outside the cell ...

Molecular pistons and redox

A redox reaction has been used to move a molecular piston back and forth. It is hoped that this will allow nanomachines to make use of it. The piston works with a man made molecule called a rotaxne. The rotaxne is a liner molecule with a napthalene complex at one end and sulfur containing group at the other end. The sliding part of the piston is made of six carbon rings, joined to form a hooped shaped positively charged ion. By ...

Metathesis

Metathesis is the name given to a particular type of chemical reaction - we may refer to the same reaction a displacement reaction. It is not a redox reaction. An example of this type of reaction is given below: Image kindly reproduced according to the licence at: http://en.wikipedia.org/wiki/File:Metathesis_reaction_Chemical_equation.png A metathesis reaction won three chemists (Chauvin, Grubbs and Schrock) the noble prize in 2005 (click here to read more) for essentially producing a catalyst that reduced the number of steps needed for chemical synthesis.