Hello, I'm Hank Green and this is Crash Course Office Hours where I take some of the questions and concerns that you had with the last episode of Crash Course Biology and answer them or address them.

We have an excellent question from MsLebbel: "What is meant by polar?" Now, when we were talking about this in the last episode, we're talking about chemical polarity which is when a molecule has a part of the molecule that's positively charged and part of it that's negatively charged. Basically the molecule has become, itself, a magnet. This happens in a variety of molecules. The reasons why it happens is very complicated, but basically the electrons around the atoms end up spending more time on one side of the molecule than on the other side and so you have a negative side and a positive side. And that is what I meant by polarity.

MartinSabatonFan wants to know if there are any other elements besides water and carbon that life could be based on, and Martin, well, we all would like to know that very much. And my impulse is that, "No! It could not possibly be possible. Everything we know is based on water and carbon." But, ya know, things that I can't imagine happen all the time in the universe, and so maybe it is possible, but I don't think we're gonna know until they come knocking on our door.

jamesahibbard asks, "Excuse me Mister Green, but isn't steam, like a cloud, not a gas, but a fine liquid?" Uh, no, not really. What we generally call steam in our everyday life, the stuff that comes out of a kettle or the the mist in our shower, isn't actually, technically, steam. That, as you say, is little tiny droplets of water floating around in the air. When scientists are talking about steam, what they mean is gaseous water, literally water that has been converted into a gas. If you walked into a room filled with steam instead of being like, "Ah, this is relaxing," you would, your face would melt off, you would die very quickly. It would be a very horrible, horrible way to die. Steam, by definition, is hotter than boiling water and it is a clear gas and it is one hundred percent water.

Phylo45 and several other people pointed out that, in fact, if ice were denser than water, icebergs sinking to the bottom of the ocean would not, in fact, raise the sea level. And this is true and I apologize for misinforming all of you. Basically, an ice cube already displaces its entire mass if it's floating in water. But if the density was higher, higher than water, and it was underwater it would actually be smaller, taking up less space than an ice cube floating on the surface of the ocean. And it's a little bit complicated. But that person and the other ones who corrected me on that, thank you.

And finally marc46o compliments me on my skill as a teacher, but wonders if I'm doing this by myself and I am certainly not. Thank you to the people who are helping me work on this. We have Jenkins back there, behind the camera. Come on out. [from back] No. [Hank] Nick is also editing these, thank you Nick. And then we have Blake and Jesslyn helping me write them, and Amber and Pete are the amazing people helping to do the graphics on these. So, thank you to all of them and I will see you very soon in the next episode of Crash Course.