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silverks

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  1. I did that question too, and I used the Theory of Knowledge text book by Nicholas Alchin (my TOK teacher said he's the chief examiner or something). If you want to take a look, you can download the particular relevant chapter (Chapter 10: Empiricism - the Use of the Senses) here: http://rapidshare.com/files/164583151/silv_TOK_empiricism.rar
  2. A very good and informative site for the Organix case study: http://wiki.khairul-syahir.com/ib/index.ph...anix_Case_Study
  3. Bonjour tout le monde!! Je m'appelle Khairul, de Malaisie. Je prend Francais Ab Initio pour IB dans Sri KDU en Malaisie. Comme Caitlin, je veux parler Francais ici pour ameliorer mon francais!! Beaucoup des aides et conseils, s'il vous plait!
  4. Hi all! I have done the first draft of my Extended Essay, and the topic is: [b]Is bacteriological agar a viable substitute for agarose in Lambda DNA gel electrophoresis and if yes, what is the optimum gel concentration for it to produce comparable results with agarose as the electrophoresis medium? [/b]Now, I'm confused. Should I register this extended essay under Biology subject or under Chemistry? My teacher said it is more to Biology, but I think it is more to Chemistry. It is basically running a gel electrophoresis of DNA with bacteriological agar instead of agarose to investigate its viability to be used as substitute. Manipulation includes using different gel concentration and preliminary research includes testing with commercial cooking-grade agar. Any help would be appreciated. This is really urgent. Thanks!
  5. thanks hamani! My teacher said ok. Just looking for a second opinion, since I'm doing IB in a new IB school and it's the first time my teacher is teaching for IB
  6. [quote name='booji' post='21178' date='Aug 1 2008, 03:12 AM']First of all, if you have access to an IR, UV-Vis, or NMR spec, get a spectra of the white powder that you have extracted. If indeed caffeine is present you should see a characteristic pi --> pi* transition in the UV-Vis spectrum, and similarly you should see characterisitc C-C stretch in the IR spectrum. This will confirm if you have indeed extracted caffeine. After that, you could try extraction of that solid with various organic polar solvents (acetonitrile comes to mind). Your best bet would be to consult the literature to see which organic solvent would work best. I am sure there are a plethora of articles on SciFinder of CSA, etc.[/quote] Even if you don't have those advanced analytical equipment like IR, UV-Vis, or NMR spec, you can use thin layer chromatography (TLC) technique to verify that it's caffeine. For this technique, you should compare the sample you obtained with a sample of pure caffeine (your school can obtain it from chem substances supplier). This technique will also tell you whether the caffeine you extracted is pure or contains impurities (the latter is more likely). About the solvent, I used dichloromethane before and it worked fine. But practise goob lab habits, though. Dichloromethane, like most other organic sovlent, is a suspected carcinogen. Always wear glove when handling them and do your extraction in a gas hood.
  7. Are you already doing IB or you'll be doing it next year? That line above is as if you're already doing IB, but you explicitly mention that you'll be taking it next year... By the way, for IB Physics, obviously HL is harder than SL, but how you fare with the subject is really up to you. If you are really interested in Physics and have a fairly good skills in mastering the physics concepts as well as familiar with some deep calculation and understanding, then you should be ok. Here in my school, the physics HL students scored better than the physics SL student, even though HL is supposed to be harder. Those taking SL are mainly humanities student, while those taking HL are engineering students, so I guess that in itself presents a reason why. If you are really looking at how different HL and SL is, you might as well take a look at the syllabus guide for IB Physics. Look for the Syllabus details - AHL. Those are the additional topics required for Higher level (AHL means Additional Higher Level). http://www.ibsurvival.com/forum/index.php?...opic=20#Physics
  8. I agree with ccccc. At my school, we're using the IBID text book, the Giancoli Physics text as well as the Physics for the IB Diploma by K.A. Tsokos. Personally, the IBID text book is good for quick revision, the Giancoli Physics text is good for fundamental understanding of the concepts but it doesn't do very well for the calculations apart and how to derive the formula. Tsokos did a very good job for the calculations and formula derivations part.
  9. [quote name='rachydean' post='19555' date='Jul 9 2008, 09:32 PM']can anyone help me!! i chose to do chemisrty ofr my exyended essay and have done the extraction of caffeine from tea bags however i have got to a point no where i only used 6g of tes but have like 5g of white-ish powder. the method i used said to add Sodium Sulfate (Na[sub][/sub]2SO[sub][/sub]4) i guess the powder is a mixture of the caffeine and the sodium sulfate but how do i get the caffeine from that. the method i have been following all the way through says to do a sublimination but im not sure any tips would be loved![/quote] Ok, 5g of that white powder obtained from 6g of tea leaves is definitely NOT caffeine. In all probability the amount of caffeine you should get is in the scale of milligrams. For 6g of tea leaves, you should be able to get around 30 to 60 milligrams of crude caffeine. If that white-ish powder is indeed the sodium sulphate, then sublimation is required to separate them. Caffeine is known to undergo sublimation at around 178 C while anhydrous sodium sulphate will melt at extremely high temperature (844 C), so you should be able to easily separate them by sublimation technique. However, you should not have gotten that much white-ish powder in the first place. I've done caffeine extraction multiple times before and managed to extract crude caffeine (what you call the white-ish powder) from 0.004g to 0.020g, depending on the brand and type of tea leaves used. If you could list out your extraction methods I may be able to help you out further.
  10. silverks

    Titrations

    Usually titration is used to measure the concentration of the solution in question. If your intention is just to measure pH, why not simply use a pH meter (assuming your school lab has one)? So far as I know, pH is not a factor in titration. As long as one solution is acidic and one solution is basic, no matter what the pH difference is, titration will work. However,you won't be able to calculate the pH for that solution, only the amount of acidic or basic molecules that are present in the solution hence being able to determine its concentration.
  11. Hi all, I'm doing IB for the Nov 2008 exam session, and am currently in the process of doing my Business IA. I'm quite in the dark about the requirement for the Research Question. I would greatly value your opinion and advice on the viability as well as how to improve this research question: [b]What are the probable methods of recruitment to help [Company Name] overcome its difficulties in recruiting new staffs that have been hindering its growth?[/b] By the way, I'm doing Business & Management at Standard Level. Thanks in advance.
  12. Hi all. I happen to have an IA sample, but it's written in the year 2002 and I guess it doesn't apply for anyone taking IB for the starting exam session May 2009. It will still help those who are taking the exam session Nov 2008, though. So, here I post it. Business_IA_Standard_Level_Example_2.pdf
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