Term 2 Week 2: Journal Entry
This week was pretty interesting. Have quite alot to blog about. For starters, we've moved ahead in both theory and practical lessons and I'm making preparations for the hong kong student science conference which i'm attending with chong yong and ernest in the 5th week along with 3 yr 4s and mr william lai. Should be quite interesting.
Anyway, beginning with practical lessons as always, we did a prac on food testing this week. For practical, we basically ran all the food test there are. Benedict's test for glucose, ioding test for starcg, ethenol emulsion test for lipids and biuret test for proteins. It was interesting to carry out the tests and see for ourselves what they produced. The iodine test was straight forward, blueblack indicated high amounts of starch, green indicated moderate amounts to trace amounts of starch and yellow-brown indicated no starch present. The interesting thing was, if you added ioding to a starch solution and it turned dark blue, you could return the solution to its original clear state by adding sodium hydroxide. Reason for this was that sodium hydroxide dissolves the iodine as iodine is soluble in sodium hydroxide and ethanol and so what's left is simply starch sollution with dissolved clear sodium hydroxide and iodine. So interesting.
For the benedict's test, also straightforward stuff, simply add benedict's solution to the sample and place in a beaker of boiled water and watch the colour change. However, it was interesting to note that if left for too long, the tube of sample would go brown indicating failed experimentation. Didn't know that. As usual, the indicators were brick red indicate high amounts of glucose, yellow/ orange indicated moderate amounts and green indicated trace amounts. Of course, no change indicated no glucose. However, we were taught that sucrose cannot be tested using this method unless hydrolised by sodium hydroxide or any weak acid. So that was one point we noted.
Ethanol emulsion test was one of the new tests that we conducted this week. Basically, adding the ethanol to the vegetable oill, swirl then add water should give a cloudy white emulsion if lipids are present. Interesting to note. We were also taught the " model answer" for noting observations:
CLOUDY WHITE EMULSION OF TINY LIPID DROPLETS FORMED
haha. anyway, on to Biuret test. Another new test to many of us, this test tests for proteins. Basically the copper (II) sulphate solution when added to the solution of sample mixed with sodium hydroxide produced a purple colouration if proteins were present. The interesting thing to note was that if benedict's solution were added, the experiment would work just as well because the benedict's solution is actually largely copper (II) sulphate, so it works just as well, if not better.
Yeah, that's the practical. Pretty interesting. and i think this might be my longest post yet. For theory lessons, we continued with nutrition. Depressing though, to note that we probably wil die at 30 of all the toxic stuff we're filling ourselves with. Cholerterol, fats of all types and sizes..... High blood pressure, dilation of arteries if clogged with fats..... imagine if someone was a frequent macdonalds patron who smoked?! He'd probably be dead by 25. The cigerette smoke and fats would likely cause him a stroke at age 20!! haha. Anyway, we learnt we all were pretty unhealthy eaters, even though we seem to eat healthy. sigh........
Anyway, I've also been studying some stuff for the HK student science conference i'm attending in wk 5. Its all about ecology and some of the practical skills involved. We've got to present a paper so we've got our work cut out for us. We've been looking into sampling techniques, quadrat samping, transect sampling, chi square, mark and recapture and the works. We also want to do a trial study here before leave so that we look like we know what we're doing, even though i bet we dont. haha. Well, taht's it for this week. I'll post about the HK science conference another time.
whispering away.........
Anyway, beginning with practical lessons as always, we did a prac on food testing this week. For practical, we basically ran all the food test there are. Benedict's test for glucose, ioding test for starcg, ethenol emulsion test for lipids and biuret test for proteins. It was interesting to carry out the tests and see for ourselves what they produced. The iodine test was straight forward, blueblack indicated high amounts of starch, green indicated moderate amounts to trace amounts of starch and yellow-brown indicated no starch present. The interesting thing was, if you added ioding to a starch solution and it turned dark blue, you could return the solution to its original clear state by adding sodium hydroxide. Reason for this was that sodium hydroxide dissolves the iodine as iodine is soluble in sodium hydroxide and ethanol and so what's left is simply starch sollution with dissolved clear sodium hydroxide and iodine. So interesting.
For the benedict's test, also straightforward stuff, simply add benedict's solution to the sample and place in a beaker of boiled water and watch the colour change. However, it was interesting to note that if left for too long, the tube of sample would go brown indicating failed experimentation. Didn't know that. As usual, the indicators were brick red indicate high amounts of glucose, yellow/ orange indicated moderate amounts and green indicated trace amounts. Of course, no change indicated no glucose. However, we were taught that sucrose cannot be tested using this method unless hydrolised by sodium hydroxide or any weak acid. So that was one point we noted.
Ethanol emulsion test was one of the new tests that we conducted this week. Basically, adding the ethanol to the vegetable oill, swirl then add water should give a cloudy white emulsion if lipids are present. Interesting to note. We were also taught the " model answer" for noting observations:
CLOUDY WHITE EMULSION OF TINY LIPID DROPLETS FORMED
haha. anyway, on to Biuret test. Another new test to many of us, this test tests for proteins. Basically the copper (II) sulphate solution when added to the solution of sample mixed with sodium hydroxide produced a purple colouration if proteins were present. The interesting thing to note was that if benedict's solution were added, the experiment would work just as well because the benedict's solution is actually largely copper (II) sulphate, so it works just as well, if not better.
Yeah, that's the practical. Pretty interesting. and i think this might be my longest post yet. For theory lessons, we continued with nutrition. Depressing though, to note that we probably wil die at 30 of all the toxic stuff we're filling ourselves with. Cholerterol, fats of all types and sizes..... High blood pressure, dilation of arteries if clogged with fats..... imagine if someone was a frequent macdonalds patron who smoked?! He'd probably be dead by 25. The cigerette smoke and fats would likely cause him a stroke at age 20!! haha. Anyway, we learnt we all were pretty unhealthy eaters, even though we seem to eat healthy. sigh........
Anyway, I've also been studying some stuff for the HK student science conference i'm attending in wk 5. Its all about ecology and some of the practical skills involved. We've got to present a paper so we've got our work cut out for us. We've been looking into sampling techniques, quadrat samping, transect sampling, chi square, mark and recapture and the works. We also want to do a trial study here before leave so that we look like we know what we're doing, even though i bet we dont. haha. Well, taht's it for this week. I'll post about the HK science conference another time.
whispering away.........
