Science Center

I went to the science center on 2th May. It was indeed a fun and enriching trip. We went around the exhibitions first. What interest me the most was the maths room where there were lots of interesting formulas such as e=mc2 and e^(i*pi) + 1 = 0 which I have no idea why. Besides going to the usual exhibitions that everyone have seen before, we also went to a science show which was about liquid nitrogen. Liquid nitrogen is a liquid colder than dry ice which boils at -196 degrees Celsius, so its actually boiling in room temperature. When we pour it on the floor, it instantly vaporizes. The experimenters also made a soft banana into a hammer by pouring liquid nitrogen on it, as the banana contains water which turn into ice, it becomes as hard as a hammer and successfully hammered a nail into a chair. But when they tried pouring liquid nitrogen on a flower, although it became hard, when we tried to hammer a nail into a chair, the flower shattered into pieces. This was because that the frozen flower was like a thin layer of ice, it is hard but brittle. Then, they poured liquid nitrogen on a rubber balloon, they used it as a nail and hammered it in. This was possible even though it did not contain water due to the properties of rubber, when rubber contracts, it loses its flexibility and becomes stiff. Next, they tried to contain liquid nitrogen, they poured some into a plastic container and capped it with a lid tightly but the lid still popped out. Then they poured some into a glass flask and covered the mouth with a balloon. The balloon inflated and finally burst. This was because when liquid nitrogen vaporizes, its volume increases by about 600 times. After that, they tried to squeeze in a lot of balloons into a small box by pouring liquid nitrogen on it, this was possible as the air contracts when it is cool and the balloon's volume becomes smaller. Then, they took out the contracted balloons and the air inside expanded and the balloon had a bigger volume. However, some of the balloons burst as the air inside expanded faster than the rubber becoming flexible. Finally, they created a giant cloud by pouring lots of liquid nitrogen into a big unsealed container and adding hot water to it, the liquid nitrogen vaporizes faster and created a gigantic cloud. As I was seating in the first row, I could feel the nitrogen vapor, it was very cooling and I could not see the thing in all of that cloud. In total, the trip was very fun and enriching, I hope to come here again.