字幕列表 影片播放 列印英文字幕 Brady's been doing some science. He discovered that when he took ice from his freezer and dropped it in his drink the ice crack, and he wondered why. This is an example of quite a common phenomenon, which is called differential expansion. When you drop eyes into your drink, the drink is warmer than the ice. The outside of the ice warms up and expands. The inside is still very cold. He can't expand. And so it just cracks because part of it's trying to get bigger and part ist thing the same. So there is essentially a tug of war between the inside and the outside, and it gives way. So the second thing Brady noticed was if he left the ice on a plate in the table for 10 minutes or so. When he put it in the drinks, it didn't break on Dhe. The reason is that his freezer is cold, probably minus 15 minus 20 C. So when it first comes out the freezer, the ice is much colder than the melting point of water, so it's minus 20 C, and the water warms it up quickly and causes the ice to expand with on the other hand, if you leave it lying around, the ice warms up to its melting 0.0 degrees centigrade. And then when you put it into the water, the ice doesn't expand, it just melts. But then I asked Brady, What did you think would happen if we dropped ice into liquid? That was really cold, So we have hot ice compared to the liquid on. We can do that very easily by dropping ice into liquid nitrogen, which is at minus 196 C. So it's very, very much colder in the ice. And, of course, he went to Neil and did the experiment, this time the outside of the ice. Instead of expanding contracts because it gets cold, the inside can't contract quickly enough, so it shatters just in the same way as it does in the drink.