This past unit in science we covered states of matter and how they change. Students have to understand how molecules move at each phase and the energy involved. There are a ton of demos that show the phase changes and this is one of my favorites. All that you need is a large flask, water, a water balloon, a hot plate and tongs. I have my students draw diagrams of how the molecules are arranged and moving at each phase and the transitions inbetween. They also have to determine if heat energy is being added or taken away in each change. Even in the digital age, I think students benefit from simple pencil and paper drawings. The drawings are really models that explain the scientific phenomena. When the balloon gets pushed into the flask, it is a very dramatic demonstration of a liquid taking up less space than a gas.
Entries in forces (16)
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).
Here on Earth, friction is an unbalanced force that will cause moving objects to negatively accelerate. A top is a classically fun toy that spins for a period of time. Tops stop spinning because of friction forces between the top and the surface it is spinning on (as well as some friction with the air). Using a top that doesn't stop (available at Educational Innovations) and a normal top, this demo offers a discrepant event for students to experience. They know that all tops stop, but don't neccessarily know why, and they will be especially preplexed when they see a top that does not stop spinning. Watch the video to see it in action and to see why it doesn't stop spinning.
This is one of my favorite demos to show how mass determines the inertia of an object. If you are going to do this demo in class, make sure you use fishing line that can handle the highest tension possible (great demo for tension as well) that you can buy at a local sporting goods store. I used goop adhesive to attach a paper clip to the golf ball, so that I could tie the fishing line to the golf ball. I tied both objects to the metal beams of the drop down ceiling in my classroom. Watch the video to see how the demo works.
At the end of the year, students get a chance to be the scientists in several projects. One of my absolute favorites is the water bottle rocket. The video shows the general design of the rockets and several launches. What I love about the project is that they chose one variable to change that will increase flight distance. Variables include fin shape, fin size, fin placement, volume of water, etc. I also love that there is not just one design that works. Here is the handout that I give to students.