Thursday, 26 May 2011

Magnetic attraction to Physics

This week students learnt about the motion of a charged particle in a magnetic field and then discussed the application for the cyclotron.
Students can look on the FLO where Mr. Haggett has put a simulation of a cyclotron.

An online quiz for students who want a bit extra can look at
Mr. Haggett - online quiz in physics

Today physics had a guest teacher Mr. Keith South 

Thursday, 19 May 2011

Oxidation of alcohols

Students have started studying organic chemistry.

Today the chemistry students did an investigation to establish the oxidation reaction patterns of primary, secondary and tertiary alcohols, using oxidising agent acidified potassium dichromate. 

If oxidation occurs, the orange solution containing the dichromate(VI) ions is reduced to a green solution containing chromium(III) ions.

In the case of a primary or secondary alcohol, the orange solution turns green. With a tertiary alcohol there is no colour change.
Orange  Acidified Potassium Dichromate
Green Chromium ions


Primary alcohols can be oxidised to either aldehydes or carboxylic acids depending on the reaction conditions. In the case of the formation of carboxylic acids, the alcohol is first oxidised to an aldehyde which is then oxidised further to the acid.

Partial oxidation to aldehydes

You get an aldehyde if you use an excess of the alcohol, and distil off the aldehyde as soon as it forms. The excess of the alcohol means that there isn't enough oxidising agent present to carry out the second stage.

Ethanol  a primary alcohol  would produce the aldehyde ethanal, CH3CHO.

Full oxidation to carboxylic acids

You need to use an excess of the oxidising agent and make sure that the aldehyde formed as the half-way product stays in the mixture. The alcohol is heated under reflux with an excess of the oxidising agent. When the reaction is complete, the carboxylic acid is distilled off.

The full equation for the oxidation of ethanol to ethanoic acid is:

Secondary alcohols are oxidised to ketones
Heating the secondary alcohol propan-2-ol with acidified potassium dichromate(VI) solution  produces propanone.

Tertiary alcohols are not oxidised by acidified potassium dichromate(VI) solution. There is no reaction.

For the next few weeks the SMAF class are fortunate to have an extra practicing teacher Dr. Paul K. Bowyer. Dr. Bowyer has a background in organic chemistry. He undertook a PhD in 1992 at UNSW on heterocyclic chemistry and metal complexation, part of which was completed at the University of Cambridge Chemical Laboratory in the United Kingdom after obtaining a Young Endeavour Science Award in 1992.  Three years of post-doctoral research in pure chemistry followed at the Australian National University (Canberra, Australia) and the Universität Basel (Basel, Switzerland).   In 2011 Dr Bowyer joined Blue H2O Filtration as the Regional Manager for SA. 
Dr. Paul Bowyer chatting to students about the oxidation of alcohols.
Paul looking at a students result.

Wednesday, 18 May 2011

Chemistry students reflect on silver mirrors

                      Students in chemistry today saw their reflections in the silver mirrors they produced.

The students were learning about Tollen's test or silver mirror test. 

        Tollen's test is a specific test for aldehydes. Silver ions are reduced to silver, which is seen as a silver mirror.The aldehyde is oxidised to the carboxylate ion of the corresponding carboxylic acid.

Wednesday, 11 May 2011

How much chlorophyll is in your olive oil?

Different substances absorb different wavelengths of light. Chemicals have their own distinctive absorption fingerprints that can be used to identify when and how much of the material is present. UV-Vis spectroscopy studies the absorption fingerprints of materials in the visible-near ultraviolet range.

Mr Anthony Armstrong Academy Chemistry Teacher explaining UV spectroscopy
Olive Oil is made by pressing and extracting the oil from olives. There are various grades of olive oil. Extra Virgin olive oil is considered the highest quality because it comes from the first pressing of the olives. It has a greenish-yellow tint because of the high levels of chlorophyll. Light olive oil is very light in colour because it has been processed under pressure to remove the chlorophyll and volatile compounds.

Chlorophyll is actually made up of four different pigments. These four pigments absorb light at different frequencies. UV spectroscopy of the chlorophyll in the olive oil creates three blue absorption peaks at 413, 454, and 482 nm, and two red absorption peaks at 631 and 669 nm. The students could compare the amount of chlorophyll in the different types of olive oil.

Chemistry that glows!

High Performance Liquid Chromatography (HPLC) is a form of column chromatography that uses high pressures to force mixtures through the column – hence speeding up the chromatography process. Students simulated HPLC using air from a wash bottle to force the mixture through a glass column. 

Students separated a mixture of polar hydrogen peroxide and sodium salicylate from the organic compound found in glow stick liquid. 

When the glow stick liquid is without hydrogen peroxide it stops glowing. After the separation using HPLC the students’ added hydrogen peroxide back to the organic compound and it started to glow again.

Thursday, 5 May 2011

Specialist Maths find a Golden Ratio

Year 12 Specialist Maths students completed their directed investigation on solving the

 Golden Ratio 

and solving the theory of chaos                                 

The Directed Investigation incorporated skills developed in Trigonometry, Complex Numbers and Polynomials.

Mr. Maurice Akele
Academy Specialist Maths Teacher 

Wednesday, 4 May 2011

Professor Warren Lawrance

Students in chemistry today experienced a teriffic presentation titled Atomic  Spectroscopy: The Absorption and Emission of Light by Atoms from the Executive Dean of Science and Engineering Professor Warren Lawrance.

Professor Lawrance presented what spectrocopy was and what it was used for in science.
He tied together a lot of the students learning so far and took it a little further.

The dark lines in the solar spectrum shown here are caused by absorption by elements
in the outer layer of the sun (and also the Earth’s atmosphere).These absorption lines allow the identification of 67 elements in the outer in the layer of the sun’s atmosphere.

The teachers and students really enjoyed listening to his latest research and discoveries on a molecule's spectroscopy and manipulation of their translational energies.

Professor Lawrence showed how science can be really exciting and a great career.

Team teaching electric fields in physics

Year 12 Physics students started a new topic today called Changes in Electric Fields

Year 12 Academy Physics Teachers Donna Riordan and Jak Haggett

Mr. Haggett showing the students how to work out a problem using a piece of technology called an ELMO 


Monday, 2 May 2011

Atomic Absorption Spectrometer

Atomic Absorption Spectrometer (AAS) is used to accurately determine the concentration of a metallic element in solution.  The procedure depends upon the fact that atoms absorb light strongly at discrete, characteristic, wavelengths which coincide with the emission lines of the particular element. The extent of the light absorbance is a direct measure of the concentration of the absorbing atoms in the sample.

The SMAF chemistry students were privileged to be able to use the AAS as they are not found in high schools. Every student was given the opportunity to use the AAS thanks to Academy Chemistry teacher Colin Grace. 

Today the students used the AAS to determine the unknown copper concentration in a water sample. 

To find the concentration of copper in an unknown solution the students first needed to draw a standard curve using solutions of known copper concentrations. The students measured the absorbance of these solutions and plotted a calibration curve for the standards solutions showing absorbance vs concentration (ppm). The students used their graph to determine the concentration of copper in the unknown solution.

Gas Chromatography

Students observing very thin gas column coil

Today one of the tutors, chemistry teacher Naomi Clark from Christies Beach High School assisted the SMAF chemistry class by demonstrating the Vernier Mini gas chromatography. In Gas Chromatography an inert carrier gas serves as the mobile phase that elutes components of a mixture from a column containing an immobilised stationary phase. The uses of gas chromatography are diverse.
Naomi Clark

Naomi injected a sample of the ester (an organic compound) as a liquid into the gas chromatography which was immediately vaporised by heating. The mobile gas phase then carried the sample into the column contained in the oven. The components of the sample separated on the column and are then carried to the detector where a response occurs. 

Organic compounds flowing out of the chromatography column are seen as a peak on a chromatograph. The amount of time it takes for a compound to exit the column after it is injected is called the retention time. With a GC, a compound can be identified from a mixture of chemicals by its retention time.

Peaks on chromatograph formed

The students were asked to use the chromatograph to analyse whether an esterification reaction occurred between ethanol and acetic acid to produce ethyl acetate (a fruity smelling ester). 

Students smelling ester


Cluster Map