Today a group of us from 4T went to VJC for some fun chemistry workshops!! We signed up voluntarily and we weren’t disappointed. (Alvin, Teng Chuan, Manfred, Jian Wei, Mervyn, Dominic, Ben Chin, Jim and Me) We went into the VJC campus, and after the registration, travel declaration and stuff, we took a walk around before entering the lab.
Our first workshop was titled: Snacks- Recipe for a Horizontally Developed Body? It was basically about what our food is made up of and what make you fat. So to get us awake he showed us some random videos…about turning water into ice and some painting video haha. But quite interesting la. He also explained how the 2008 compound of the year- melamine, increases the protein level in milk, haha. Anyway the lesson proper, first part is about the stuff we learnt in bio, like all the carbohydrates, lipids and proteins, plus trans fats. But then the second part was about reading nutritional labels on food. And like how calories are used in our body- 60% on Basal Metabolic Rate, 30% on Movement and 10% on Dietary Thermogenesis. Also how to gain weight, haha, for those underweight people! LDL (“bad”)and HDL (“good”)cholesterol, and about the only food with negative calories! The celery! Im just writing out the concepts, find out why yourself! Or ask the people who went! =D
Then we had an activity where we were all given something like this:
Regret not going right…lols. Anyway, we could choose to keep what we were given, or do a one to one swap among ourselves, where we could exchange something we don’t like for something we like. And at the end, the calorie values were given and we could actually measure how much we would have gotten. Mr Lim told us that, the amount of calories given at the start was actually what is required in a meal, about 600+ calories, but we wont feel full even after eating whats in the bag! Due to the nature of the food…hmm…think about it…Oh and yes, we got to keep the food. =P haha.
Ok so after that we sort of had an empty slot, so we went out to lunch together at Parkway Parade. It was quite fun going all the way there to eat, at least something different from the usual J8. Hm..ok maybe not, cos we still ate at a restaurant J8 has in the end… Well, after lunch some people had a change in plans…
Anyway, we* went back to VJC and had our second workshop titled: Going Bananas!- The Chemistry of Flavours. We learnt that flavor is actually a combination of taste, sensation and colour transmitted by receptors in the taste buds. And esters are a key component of the aromas of fruits (carry the bulk of the signals). Esters tend to have distinctive, generally pleasant odours, and are made from the reaction between carboxylic acids and alcohols. Flavours are usually created using a complex mixture of esters, and food manufacturers use them to make artificial flavouring.
We learnt 2 methods of synthesizing esters. Method 1 is simpler to understand: Condensation reaction of alcohol with carboxylic acid. The 2 chemicals we used are Methanol and Butanoic Acid, and we also needed to use c. sulfuric acid as catalyst, and heat it over a boiling water bath. Cant heat it over a naked flame, as alcohol is flammable. We got a smell closest to that from an apple from this experiment! Ok, fine we couldn’t really tell that well…(remember a flavor is made up of a combination of esters?) But still we had to learn how to draw the structure of the methanol and butanoic acid, and how they eventually formed the ester with the apple smell, and of course water, being a condensation reaction. The very nice teacher’s assistant taught us this! (something like Xin Yan, Yen San or Zhao Yuan…haha) So we had to know how to identify an ester. It’s a C with one single C-O bond and one double C=O bond, so it’s like O-C=O. That’s an ester.
As for Method 2, the reaction of alcohol with ethanoic anhydride, it was basically similar steps in doing it, but adding different stuff. We added alcohols such as: Octan-1-ol, Propan-1-ol or 3-methyl-1-butanol, to an acid derivative, Ethanoic Anhydride. Think its because the acid derivative is more reactive… So, from these, we got the smells of orange, pear and bananas!! (respectively) Again, these smells aren’t that obvious, except for the banana, which most of us are able to tell because it has a more distinct smell. Really nice! Haha. After that, this time, they only showed us the chemical formulas for the substances, and wanted us to draw out the structures of the esters that would form as a result. Slightly difficult to understand at the start, but simple once you get the hang of it, haha. Its quite interesting how they are able to tell the information of the substance from its name…like the prefixes: Met means 1 C, Eth means 2 Cs, Prop is 3 Cs, But is 4Cs, and Hep is 5Cs. (a lot of Singaporeans like Hep? Haha!) The teacher said that we are going to learn this in organic chemistry! And, we have to remember up to 10 Cs for our A levels…yea so learn 5 first lor… and then also if the name ends with –ol then its an alcohol, with an OH functional group…yea this sort of thing.
We were also supposed to do it in something called the reflux setup, which actually just means heating with an attached condenser which helps to condense the vapours which evaporated back into liquid form for heating, as the organic compounds are very volatile.
This second workshop has a lot more new content for us, still the level pitched was okay, not too difficult or easy, so its understandable la. We were a bit overwhelmed at first, but after a while, with some help from the assistants, we were good to go, haha. And its quite fun to get to conduct the experiment yourself, and smell the fruit flavouring you created!
Overall, I enjoyed both the workshops very much! And we had quite a fun time engaging in the activities while having learning chem! These workshops have given me a chance to get to see more of the uses and applications of chemistry! =)
