This product comes with 2 seemingly identical black squares. I pass them around so that students can see that there is really nothing different between them. This then becomes the spring board to a discussion about heat transfer. It also leads into some inquiry based labs with other materials.
Kids absolutely love this little toy! The Newton's cradle is way to show energy transfer, and to start the discussion of the different energy forms. The cradle eventually slows to a stop, so students are able to revisit the Energy Conservation Law and learn that energy can be transferred into a variety of different forms, including sound.
This year I'm utilizing the windmill generator show here. Over the past several years, I've had students learn the design process by having them create the perfect blade design. It becomes a contest and a very heated one at times. I've built my own contraption using PVC pipes, but wore it out. Last year I used a different product by this company (they no longer carry it) that was nice, but not very user friendly in a classroom of 25 students all wanting to test, tweak, and test again. So this year we will be trying out the Windmill Generator, but I also hope to utilize some of the solar products as well.