1 00:00:02,040 --> 00:00:09,520 Speaker 1: Welcome to brain stuff from How Stuff Works. Hey, I'm 2 00:00:09,600 --> 00:00:12,840 Speaker 1: Christian Saga and this is brain stuff pop quiz. I'm 3 00:00:12,880 --> 00:00:15,280 Speaker 1: thinking of a substance. Let's see if you can guess 4 00:00:15,360 --> 00:00:19,040 Speaker 1: what it is. And it's pure form. It's odorless, tasteless, 5 00:00:19,120 --> 00:00:22,720 Speaker 1: and nearly colorless. It's in your food. In fact, a 6 00:00:22,840 --> 00:00:25,360 Speaker 1: lot of the stuff you use every day either contains 7 00:00:25,400 --> 00:00:29,160 Speaker 1: it or was manufactured using it. It's even in your body. 8 00:00:29,240 --> 00:00:31,639 Speaker 1: Can you guess what it is? If you guessed water, 9 00:00:31,800 --> 00:00:34,320 Speaker 1: then you're correct. Water is one of the most important 10 00:00:34,320 --> 00:00:37,240 Speaker 1: substances on earth as far as life goes, at least, 11 00:00:37,479 --> 00:00:40,519 Speaker 1: and it can do some weird stuff. For example, it 12 00:00:40,600 --> 00:00:44,440 Speaker 1: reaches a maximum density at around four degrees celsius and 13 00:00:44,440 --> 00:00:48,440 Speaker 1: then becomes less dense before it freezes. And here's another 14 00:00:48,479 --> 00:00:52,320 Speaker 1: strange thing. Hot water can freeze faster than cold water. 15 00:00:52,600 --> 00:00:56,400 Speaker 1: But why, Okay, this is a very old question. In fact, 16 00:00:56,440 --> 00:01:00,200 Speaker 1: Renee Descartes thought about it, and Francis Bacon before him, 17 00:01:00,320 --> 00:01:04,360 Speaker 1: Aristotle pondered the mystery too. Today we call this phenomenon 18 00:01:04,480 --> 00:01:08,880 Speaker 1: the Impemba effect, after a guy named Erasto Impemba, who 19 00:01:08,920 --> 00:01:11,440 Speaker 1: first observed the effect on ice cream when he was 20 00:01:11,520 --> 00:01:15,040 Speaker 1: just thirteen years old. His teacher, for the record, laughed 21 00:01:15,040 --> 00:01:18,800 Speaker 1: at him, Well who's laughing now? Turns out Rasto was 22 00:01:18,840 --> 00:01:21,679 Speaker 1: onto something big, and teams of experts would spend the 23 00:01:21,720 --> 00:01:25,160 Speaker 1: next few decades trying to explain why water behaves this way. 24 00:01:25,560 --> 00:01:28,800 Speaker 1: Scientists around the world cooked up dozens of theories, and 25 00:01:28,880 --> 00:01:32,160 Speaker 1: none were able to completely explain the process. But as 26 00:01:33,360 --> 00:01:36,800 Speaker 1: that may have changed. A research assistant at the University 27 00:01:36,800 --> 00:01:40,559 Speaker 1: of Zagreb in Croatia claims that convection currents in warm 28 00:01:40,600 --> 00:01:43,919 Speaker 1: water cause it to cool more rapidly, and the Royal 29 00:01:43,959 --> 00:01:47,240 Speaker 1: Society of Chemistry agrees with him. They actually gave the 30 00:01:47,240 --> 00:01:50,920 Speaker 1: guy a thousand pound prize for his experiments. But he's 31 00:01:50,960 --> 00:01:54,160 Speaker 1: not the only contender for a solution. A team of 32 00:01:54,200 --> 00:01:58,640 Speaker 1: physicists at the Non Young Technological University in Singapore took 33 00:01:58,680 --> 00:02:02,080 Speaker 1: the question to a much smaller level. They claim that 34 00:02:02,120 --> 00:02:05,080 Speaker 1: the answer lies in the bonding. Not you know, hanging 35 00:02:05,080 --> 00:02:09,560 Speaker 1: out with friends type bonding, but molecular bonding two kinds actually. 36 00:02:10,040 --> 00:02:13,200 Speaker 1: You see, every water molecule is made of two hydrogen 37 00:02:13,240 --> 00:02:17,000 Speaker 1: atoms bonded to a single atom of oxygen. These are 38 00:02:17,040 --> 00:02:21,200 Speaker 1: covalent bonds, which means that they share electrons between one another. 39 00:02:21,639 --> 00:02:25,120 Speaker 1: This is a chemical bond. Separate water molecules are bound 40 00:02:25,120 --> 00:02:28,200 Speaker 1: to their neighbors by weaker hydrogen bonds, which occur when 41 00:02:28,200 --> 00:02:31,480 Speaker 1: a hydrogen atom from one water molecule is close to 42 00:02:31,480 --> 00:02:35,480 Speaker 1: the oxygen atom of another water molecule. This is an 43 00:02:35,480 --> 00:02:39,320 Speaker 1: electromagnetic attraction and it's what gives water some of its 44 00:02:39,320 --> 00:02:43,160 Speaker 1: strange abilities, like it's unusually high boiling point of one 45 00:02:43,240 --> 00:02:47,120 Speaker 1: hundred degrees celsius that's two hundred and twelve degrees fahrenheit. 46 00:02:47,720 --> 00:02:51,040 Speaker 1: So these scientists in Singapore argue that the Impemba effect 47 00:02:51,120 --> 00:02:54,280 Speaker 1: comes from an interaction between the covalent bonds, you know, 48 00:02:54,360 --> 00:02:58,400 Speaker 1: the inner water molecule bonds, and the hydrogen bonds between 49 00:02:58,520 --> 00:03:02,680 Speaker 1: different molecules. Here's how they think it works. When water 50 00:03:02,760 --> 00:03:07,000 Speaker 1: molecules are close together, their natural repulsion causes the covalent 51 00:03:07,040 --> 00:03:10,920 Speaker 1: bonds to stretch and store energy. As the water warms up, 52 00:03:11,160 --> 00:03:14,960 Speaker 1: it becomes less dense, the hydrogen bonds stretch as the 53 00:03:15,000 --> 00:03:19,320 Speaker 1: molecules move further apart. When these hydrogen bonds stretch, they 54 00:03:19,360 --> 00:03:22,760 Speaker 1: allow the covalent bonds to shrink and release their energy. 55 00:03:23,160 --> 00:03:26,480 Speaker 1: This is equivalent to cooling. So according to the non 56 00:03:26,560 --> 00:03:30,680 Speaker 1: Young theory, hot water is essentially able to release energy faster, 57 00:03:31,120 --> 00:03:33,880 Speaker 1: leading to a quicker freeze. It's important to note that 58 00:03:33,919 --> 00:03:36,920 Speaker 1: at this point that work hasn't been peer reviewed, so 59 00:03:36,960 --> 00:03:39,560 Speaker 1: it's not a sure thing yet, but even if it's 60 00:03:39,600 --> 00:03:42,600 Speaker 1: just a contributing factor, it's a promising lead to a 61 00:03:42,680 --> 00:03:51,360 Speaker 1: question that's puzzled humanity for some twenty hundred years. Check 62 00:03:51,360 --> 00:03:53,440 Speaker 1: out the brain stuff channel on YouTube, and for more 63 00:03:53,480 --> 00:03:56,000 Speaker 1: on this and thousands of other topics, visit how stuff 64 00:03:56,000 --> 00:04:10,520 Speaker 1: works dot com.