Tuesday, June 7, 2011


The focus of this project is to extract caffeine from black tea, for example the bags of milk tea we brew. With Calcium Carbonate added with 10 bags of black tea and 500ml of hot water, we would brew the tea, and extract caffeine with the help of separation methods using the help of funnels. We were first supposed to filter out the residue using the Buchner Filter. Then, we would use the separating funnel. We also used the Rotary Evaporator, which made the last caffeine become powder-like. Afterwards , we had a demonstration of the effect of dry ice and liquid nitrogen. The professor firstly place the universal indicator solution in plain water. The colour of the water changed to green in colour. Afterwards, she place some alkaline water in the water, and the water turned purple. She added a few pieces of dry ice in the water, and the water changed colour to getting more and more acidic. The changing of colour stopped when the acidity of the water is around pH 5.

She also demonstrated using liquid nitrogen. She placed the gloves in the liquid nitrogen, and took it out, stepped on it, and the whole glove crumpled and crush. A few seconds later, the glove went back to the original shape. Afterwards, she took a frying pan and cracked open a raw egg, poured some liquid nitrogen in. A few seconds later, a frozen raw egg was seen, with the whole frying pan freezing. The pan went back to its original temperature after 10 minutes, and the raw egg still have not returned to its original shape at the end. The professor also tried to make ice cream with Coffee, milo and liquid nitrogen, along with a little bit of dry ice. She mixed the coffee, milo and liquid nitrogen, with a helper, and stirring the mixture at the same time. To make a fizzy effect like soft drinks, she also added a little dry ice into the mixtures. Afterwards, we see a coffee milo ice cream with fizzy effect made.

She also placed a half blown balloon on top of the beaker filled with liquid nitrogen, the air in the balloon contracted after a while, as the temperature of the liquid nitrogen is too low (-196degree celcius).

Rubber materials like the tubes when place into the liquid nitrogen, it can be broken by a hammer.

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