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Kitchen Chemistry

Kitchen Chemistry. 29.10.11 b y Elina Näsäkkälä e lina.nasakkala@syk.fi. What is the importance of the topic ?. Students often do not understand what is the use of the chemistry knowledge in their everyday life.

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Kitchen Chemistry

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  1. Kitchen Chemistry 29.10.11 by Elina Näsäkkälä elina.nasakkala@syk.fi

  2. What is the importance of the topic? Students often do not understand what is the use of the chemistry knowledge in their everyday life. Kitchen chemistry hopefully increases their understanding, chemistry is a part of their everyday life.

  3. Reasons for chosing my subtopics: C-vitamindetermination • teaches how go about the chemical analysis Enzymesfromlettuceleaves • allows the high level theory teaching Makeyourown ice cream - students get the chance to practise their creativity

  4. Sensory test: Can you tell the difference between natural vanilla or ethylvanillin?

  5. C- vitamin determination The method: DCPIP(dichlorophenol-indophenol) is a redox dye DCPIP (blue) + H+ → DCPIPH (pink) DCPIPH (pink) + VitC→ DCPIPH2 (colorless) C6H8O6 + C12H7NCl2O2 → C6H6O6 + C12H9NCl2O2

  6. The oxidation of L-ascorbate (C-vitamin) + 2H+ + 2e-

  7. hands on • prepare a tabletsolution (the bestcolourintensitywillbe, whenyoudissolve 2 tablets into 100 ml of water; 0,5 mg/25 ml; 1 tablet /50 ml) • prepare samplesolutions (cutpiece of yellowbellpepper of about 10 g and recordmassaccurately; chopuppiece in to about 1 cm3pieces and, in a plasticcontainer, add 10-20 cm3 of 0,1 M ethanoicacid, usehandblender to blend the mixture, eliminating as manysolidpieces as possible), • titrate by a burette or by Finnpipettes • analyze the result (freshyellowbellpeppercontainsapproximately 180 mg/100 g)

  8. Enzyme research • extract the enzyme catalase from lettuce leaves(chop up them in a plastic container and add half of the volume of the juice water • sett up the experiment • perform the experiment • plot the graph • find the Ea activation energy

  9. One set of experimental results

  10. Finding the Ea rate = k∙[H2O2]x , where k = A∙e-Ea/RT rate = A∙e-Ea/RT ∙[H2O2]x rateinitial = A∙e-Ea/RT ∙c, where c is constant in all different temperatures ln rateinitial = lnA- Ea/RT + ln c ln rateinitial = lnA- Ea/R∙1/T

  11. Plotting the graph

  12. Calculations • rate inital = 10/30 ml/s; 1/T = 0.00341 K-1 • rate inital = 15/30 ml/s ; 1/T = 0.00330 K-1 • rate inital = 20/30 ml/s ; 1/T = 0.00319 K-1 • rate inital = 25/30 ml/s ; 1/T = 0.00310 K-1

  13. Plotting a graph again

  14. Activation energy Ea Ea/R = 0,923/ 0,00031K-1 Ea =R∙0,923/ 0,00031 K-1= 24742 J/ mol ≈ 25 kJ/mol Compare, the Ea without the catalyst is 75 kJ/mol

  15. Make your own ice cream What to do • Put 2 cups of crushed ice and ¼ cup of rock salt into the quart-sizezip-closebag. Pour the milk(1/4 cup), heavy cream(1/4 cup), sugar (2 tablespoon)and vanilla(1/2 tablespoon) into the sandwich-sizebag. Sealthisbagtightly. • Place the smaller bag inside the larger bag. Gentlysqueeze out the air and sealitcarefully. Continuesqueezingitgently for about 5 minutes. What is happening inside the bag? • Drain the water from the larger bag, and add the remaining ice and salt. Seal and squeezeuntilmixture is verythick. • Remove the smallbagfrom the ice and dry the outside of the bag. With scissors, cut a bottomcorneroff the smallbag and squeeze the contents into smallbowls. Enjoy!

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