As a new teacher (high school science), I'm working to make my classes as engaging, inspiring, relevant, and memorable to the students as possible. I'm not so concerned that they learn particular factual details, but that they develop an appreciation for scientific study and begin to adopt the habits of mind that it entails: curiosity, cause and effect reasoning, attention to detail, persistence, acceptance of uncertainty, etc.
So, my question to the community here is this: if you have a fond memory of a chemistry (or biology, geology, physics) class, a lesson, or a project, what made it memorable? Maybe there was a lesson where you realized you had misunderstood something important and then it all came clear, or a project that captured your imagination, or a topic that you didn't know you needed to know until it came up.
If you're a science teacher and you have a particular lesson or unit that seems to really connect with students, please share that, too.
I'll offer some of my better lessons/units in the comments below, but I don't want to start with them here because I don't want to prejudice your own ideas -- I don't want to create a frame that leads to a lot of similar things.
I'll be around to chat in the comments. Thanks, in advance, for your ideas!