Speaker 1: Welcome to brain stuff from How Stuff Works. Hey, I'm
Speaker 1: Christian Saga and this is brain stuff pop quiz. I'm
Speaker 1: thinking of a substance. Let's see if you can guess
Speaker 1: what it is. And it's pure form. It's odorless, tasteless,
Speaker 1: and nearly colorless. It's in your food. In fact, a
Speaker 1: lot of the stuff you use every day either contains
Speaker 1: it or was manufactured using it. It's even in your body.
Speaker 1: Can you guess what it is? If you guessed water,
Speaker 1: then you're correct. Water is one of the most important
Speaker 1: substances on earth as far as life goes, at least,
Speaker 1: and it can do some weird stuff. For example, it
Speaker 1: reaches a maximum density at around four degrees celsius and
Speaker 1: then becomes less dense before it freezes. And here's another
Speaker 1: strange thing. Hot water can freeze faster than cold water.
Speaker 1: But why, Okay, this is a very old question. In fact,
Speaker 1: Renee Descartes thought about it, and Francis Bacon before him,
Speaker 1: Aristotle pondered the mystery too. Today we call this phenomenon
Speaker 1: the Impemba effect, after a guy named Erasto Impemba, who
Speaker 1: first observed the effect on ice cream when he was
Speaker 1: just thirteen years old. His teacher, for the record, laughed
Speaker 1: at him, Well who's laughing now? Turns out Rasto was
Speaker 1: onto something big, and teams of experts would spend the
Speaker 1: next few decades trying to explain why water behaves this way.
Speaker 1: Scientists around the world cooked up dozens of theories, and
Speaker 1: none were able to completely explain the process. But as
Speaker 1: that may have changed. A research assistant at the University
Speaker 1: of Zagreb in Croatia claims that convection currents in warm
Speaker 1: water cause it to cool more rapidly, and the Royal
Speaker 1: Society of Chemistry agrees with him. They actually gave the
Speaker 1: guy a thousand pound prize for his experiments. But he's
Speaker 1: not the only contender for a solution. A team of
Speaker 1: physicists at the Non Young Technological University in Singapore took
Speaker 1: the question to a much smaller level. They claim that
Speaker 1: the answer lies in the bonding. Not you know, hanging
Speaker 1: out with friends type bonding, but molecular bonding two kinds actually.
Speaker 1: You see, every water molecule is made of two hydrogen
Speaker 1: atoms bonded to a single atom of oxygen. These are
Speaker 1: covalent bonds, which means that they share electrons between one another.
Speaker 1: This is a chemical bond. Separate water molecules are bound
Speaker 1: to their neighbors by weaker hydrogen bonds, which occur when
Speaker 1: a hydrogen atom from one water molecule is close to
Speaker 1: the oxygen atom of another water molecule. This is an
Speaker 1: electromagnetic attraction and it's what gives water some of its
Speaker 1: strange abilities, like it's unusually high boiling point of one
Speaker 1: hundred degrees celsius that's two hundred and twelve degrees fahrenheit.
Speaker 1: So these scientists in Singapore argue that the Impemba effect
Speaker 1: comes from an interaction between the covalent bonds, you know,
Speaker 1: the inner water molecule bonds, and the hydrogen bonds between
Speaker 1: different molecules. Here's how they think it works. When water
Speaker 1: molecules are close together, their natural repulsion causes the covalent
Speaker 1: bonds to stretch and store energy. As the water warms up,
Speaker 1: it becomes less dense, the hydrogen bonds stretch as the
Speaker 1: molecules move further apart. When these hydrogen bonds stretch, they
Speaker 1: allow the covalent bonds to shrink and release their energy.
Speaker 1: This is equivalent to cooling. So according to the non
Speaker 1: Young theory, hot water is essentially able to release energy faster,
Speaker 1: leading to a quicker freeze. It's important to note that
Speaker 1: at this point that work hasn't been peer reviewed, so
Speaker 1: it's not a sure thing yet, but even if it's
Speaker 1: just a contributing factor, it's a promising lead to a
Speaker 1: question that's puzzled humanity for some twenty hundred years. Check
Speaker 1: out the brain stuff channel on YouTube, and for more
Speaker 1: on this and thousands of other topics, visit how stuff
Speaker 1: works dot com.