Because my students don't really relate to the concept of "computer programming" I chose to relate Scratch to having your own personal robot. You could program your robot to clean your room, move around your house, etc. We were going to do the same with Scratch. I also tied Scratch to creating video games, since this is something they are enormously interested in.
After briefly reviewing the 4 main sections of the Scratch interface I began by demonstrating the "move 10 steps" block. When the students saw that little cat move the light bulbs over their heads were immediately blinking. I then showed them the result of changing the 10 to 1 or 100.
From here I began to introduce new aspects of Scratch by posing problems.
"Wouldn't it be better if we could just get our character to walk across the screen without having to keep double-clicking this block?" So I showed them the Forever block.
"Now our guy is off the screen, how can we keep him from running off?" -- edge, bounce.
"Oops, he's bouncing back upside down...." -- Changing rotation mode.
"The guy is only going in a straight line, I want him to go all over." -- Blue direction line.
So the first part was motion, and by now the students were pretty excited. So the next step was to put in a quick background and then tell them their task.
"Today, you will be creating a scene with a background, and at least two characters that move. Let's do one together, quickly. Let's make a fish tank."
This was entirely inspired by the aquarium animation that is included with Scratch. I started a new project, chose the underwater background, and showed the students how to change the cat costume to a fish. From there we repeated the motion-steps we previously explored.
Somewhere along the way I also showed them how to resize the sprites, how to create new sprites, and how to copy sprites. I also showed them about using the green flag block to start their scripts.
This was the whole lesson. To reign in their curiosity, especially concerning sounds, I told them that as long as they made a background with two moving characters they could explore other parts of the program on their own, but I wasn't going to show them how to do any of the other things until the following weeks.
I would rate this lesson as a big success. In a very short amount of time the students were able to get very creative with just the small bit that I showed them. They also had a huge amount of curiosity towards some of the other aspects of Scratch that I didn't show them, especially adding sounds.
My plan for lesson two, which I'll be starting tomorrow, is to introduce the concepts of sound and animation. That will probably be plenty...if not, I may also throw in the "Say" and "Think" blocks. I'm very excited!