Discrepant events are the cornerstone of a constructivist science education. A good demo will force a student to confront their preconceived notion of how a phenomena works. Students must work at trying to resolve the conflict between what they just saw and their prior knowledge. Magic tricks are a perfect example of that. Students think what they just saw is magic or they try to figure out how the magic trick works. This is a simple magic trick that involves the scientific concept of friction (and a little bit of tension).
Finding things to look at under the microscope is pretty easy. This video shows a great source of microorganisms that can be found at any school. What is interesting is how to view and share what you are looking at. I purchased a Skylight smartphone adapter for a microscope. The idea is to attach the camera of a smartphone to a microscope and use the smartphone as a monitor and a picture/video recorder. It's a great concept in theory, and the reality isn't too bad. It takes a bit of time to adjust the adapter so that video/pictures come out looking acceptable. I got to thinking that students might be able to use their smartphones, without the adapter, although picture/video quality won't be as good. I think that if students got to record what they see through the microscope they could share their observations with each other and basically become the teacher/mentor to each other. Google has recently created Google+ Events. With Events a teacher can invite students to share pictures of a nucleus from an onion cell. Students can take a picture and share it instantaneously via "party mode". Other students would be able to see the pictures and they can comment if they think it's correct or not and add a picture of their own. This would lead to a more interactive dynamic between the students and the teacher would not have to go from microscope to microscope to verify if students were getting it or not. I think this would lead to many possibilities in the classroom. I look forward to testing this out.
At my middle school there are a few lab activities where hand washing is essential (those with strong acids, toxic chemicals or salmonella with the chicken wing dissection). Getting middle schoolers to wash their hands is not the easiest thing to do. That is why I like to do a demo that clearly illustrates the need. All that is needed is Glo Germ, a blacklight, and some sort of stuffed object.
It's that time of year where school is starting and that means teachers have to go over the safety rules in the science classroom. Teachers who teach chemistry must have all of their students wear safety goggles during lab activities. Being a teacher, whose middle school students don't really want to wear them, I have a simple demo for students to understand the need to wear them.