Be Specific...

There are so many different things you can try to teach in a single lesson.  Imagine, for a minute, that you want to cover the history of technology.  What will you teach?  Will you cover the general history of all technology, or delve more into one or more specific ones?

Both in my classroom observations as well as my peer observations, it has seemed to me that, in general, it is better to try to be specific.  There are occasions where a general overview is desired.  To continue the hypothetical situation, it might be good to start with an overview of all the different ways technology has grown, perhaps covering how almost everything we have is related to some technology.

But if you are teaching an entire ninety minute period on tech's history, you can cover a lot of topics and not teach very much.  I really liked some of the discussions I have been involved with where we discussed picking something specific and trying to tease out the point you are trying to make.

Following that line of thought, suppose instead that you decided to teach the history of technology and that you pick the engine as your subject.  You can still pull history out by looking at what makes the engine possible (the wheel, coal or gasoline (for steam or internal combustion), smelting to get better metals, etc.) and thus get the point across about how things have changed or grown without trying to also cover textiles, circuits, agriculture, etc.

Both examples have merit, and depend on what your goal is as a teacher for that particular lesson, but I think that, personally, I will be leaning towards the specific topics, making sure to instruct my students to look for similarities in other forms of technology.