Kate the Chemist: Water is a freak substance. Here’s why. | Big Think

When you boil water, what you are doing is making sure that the temperature of your water is so hot, basically as hot as it possibly can be, before all the hydrogen bonds break and the water itself goes from the liquid state to the gas. So, when we're looking at water, that happens at a hundred degrees Celsius, which is around 212 degrees Fahrenheit.

When we do that, we bring the thermal energy of the water up to a high temperature that any viruses or bacteria that are inside that water actually are killed, if and only if you boil that water for at least five minutes. So, the recommendation is five minutes. When I am boiling my water—because we had an issue here in Austin about a year ago where we had to make sure we had very safe water—we have to protect it.

When I boil my water for that, I boiled it for 10 minutes just because I'm a little bit of a freak, or I like to overkill things. But what you want to do is you’re basically making sure that there's enough thermal energy inside that water that it makes sure that the viruses and the bacteria that are currently in there can no longer survive.

So, it's about getting the temperature hot enough and keeping it there for a long enough period of time to make sure all those viruses are killed. Water is a freak, and so it is one of my favorite molecules ever because it has these unique properties, and we are surrounded by it constantly. We also are made of water; we have to drink water to survive. As some of us like to swim, we’re always inside of water, so it's a really, really fun molecule to investigate.

What's cool about water is it has these things called hydrogen bonds. So, what that means is it forms an intermolecular force between one water molecule and another water molecule. The oxygen on one water molecule is partially negatively charged, and so that oxygen is somewhat attracted to the partially positively charged hydrogens on another water molecule.

So, oxygen from this one, hydrogen from this one, are attracted to each other, and that certain thing is called a hydrogen bond. The distance, or the length of the hydrogen bond, or the distance between the molecules is what sets how much space those water molecules take together.

A glass of water contains a ton of different water molecules, and they all have different hydrogen bonds between them. So, when you take a chunk of water, like, and put it in an ice cube tray and then you put it into your freezer, we're going to see that the water actually expands.

So, water is super weird. This is not a normal thing, but when it goes from the liquid state to the solid state, the distance and the length of those hydrogen bonds actually increases. So, water is actually more stable in the liquid state, which is super rare; that's just uncommon. But it is what it is; like, that's what water does, and we round it all the time.

So, there's your answer. Get smarter faster with new videos daily at 5 a.m. Eastern.