This week at college has been a very busy and tiring week. I am pleased to say my UCAS form is finally complete; my personal statement is finally finished and has been proof-read by virtually anyone who sits still long enough! All that is left to do now is to ask (beg) my teachers for (good I hope) references, and then I’m all set! I can honestly say it’s an utter relief to get it finished, the thought of finishing my UCAS and personal statement has been hanging over me like a cloud, and getting it done feels like a huge weight has been lifted.
This week also documented a huge number of experiments, I am excited to say. A record four experiments, three for chemistry and one for physics, and though they may only be quick demonstrates to illustrate a particular point, I still get a thrill by getting hands on in the labs!
In chemistry, we were looking at aromatics compounds, such as phenolic compounds and started working on carbonyl compounds. We firstly performed some tests the phenolic compound methyl-4-hydroxylbenzonate, which was less corrosive than pure phenol. We tested it’s solubility in water and the pH of the resulting solution; we then tested phenolic compound’s solubility in alkalis. We concluded that the compound had acidic properties and though was slightly soluble in water, had much better solubility in alkalis. We also tested the phenolic compound’s action with sodium carbonate and bromine. We found that though the compound had acidic properties, it did not have the strength to displace the carbonate ion and evolve carbon dioxide, however, the compound did have the ability to react with bromine, discolouring bromine water and forming a white precipitate of a bromine containing compound. Finally we tested the phenolic compound with iron(III) chloride which is the common test for most phenol groups; the solution produced an intense purple colour giving a positive indicator of a phenolic functional group. Once we had finished with phenol’s we moved on to look at carbonyl compounds, aldehydes and ketones. We began by looking at the oxidation of range of primary, secondary and tertiary alcohols, as well as aldehydes and ketones. We took samples of each chemical, and gently heated them an oxidation agent (acidified sodium dichromate) to determine which oxidised and which did not. We could tell where oxidation occurred by the characteristic change of colour of the oxidation agent, from orange to green. We concluded that acidified dichromate can be used to test for carbonyl compounds; however, the test was not specific and could not distinguish between alcohols and carbonyl compounds. A better test for the presence of carbonyl compounds was 2,4-DNPH (Brady’s Reagent), this produced a bright yellow/orange precipitate in the presence of carbonyl compounds. We also used a test to distinguish an aldehyde functional group of RCHO from the ketone functional group of ROR, by using Tollen’s reagent (ammoniacal sliver nitrate) in the presence of an aldehyde functional group, Tollen’s oxidised it, producing a carboxylic acid and an electron to reduce aqueous Ag+ ions to silver, which produced a characteristic silver mirror.
In physics we were investigating circular motion, looking at centripetal acceleration and centripetal force. We took a rubber bung, tied it to a piece of string, fed it through a plastic tube and placed weights at the other end of the string. We measured a length of string (to be our radius r) and took it in turns to add different masses of weights to the end of the string and swing the equipment in a circular motion, timing how long it took to complete ten revolutions of the circle. We then used our values to determine the speed of the bung and used these values to plot a graph of Force (of our masses) against velocity squared. This allowed us to perform a little mathematics to work out the mass our bung from the gradient of the F against V2 graph, and compare this to our real life mass of the bung measured with a digital balance.