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GUOLONG: That is Friday in one of the classrooms of Building 26, 11:00 AM. MARZIEH: So I was quite nervous. SHAWN: The first day is a little bit nervous for me. CARLA: I was nervous. I'm not going to deny it. NARRATOR: Facing your students for the first time can be a little scary, but it's also an opportunity to establish that your class will be user-friendly. BILLY: I think the first day of class really sets the tone for the rest of the semester. NARRATOR: How can you set the right tone? As they make their way to your classroom on the first day, what qualities are your students hoping for? BILLY: Being knowledgeable and understanding the concept. ADRIAN: And you need to feel that you can approach them. CHANDLER: Have just an air of confidence. ADRIAN: Being easy to understand. BILLY: And being enthusiastic. CHANDLER: Being there, having a presence, having a lesson plan ready. CAROL: They're well-organized. NARRATOR: That may sound like a lot. Let's start ...

As I mentioned last Friday, there is one more topic that I want to cover. And that is the topic of diffusion. And so today, I'm going to talk about diffusion, which will be in the context of what diffusion depends on and how do we describe it. And in particular, there's two laws, Fick's first law and Fick's second law, that I want to talk about. And I want to talk about how this looks in the context of some of the chemistry that we've learned, some of the things that we've learned. So diffusion, this is kind of a standard picture people show for diffusion, although really, this is probably mostly convection, which is the movement. It's not diffusion. But diffusion kind of has taken on this broader meaning. And so what do we mean by diffusion? Well, diffusion comes from the Latin word diffundere. And that means to spread out. But in this class, we're going to start by thinking about it as a particular movement down a concentration gradient. ...