Students often have misconceptions about certain science concepts. They occur naturally and they do not happen because a student is not intelligent. The human brain tries to fit information in an easy to digest construct, even though it is not accurate. Misconceptions are very difficult to break. The best way for students to break their misconception is to articulate their understanding and then try confront a demo or new piece of information that contradicts that misconception.
In the video some teachers are asked the question, "What causes the phases of the moon?" They then are asked to demonstrate their thinking and to explain how it works. An explanation and demonstration of how the phases of the moon actually happen takes place in the last third of the video.
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.
Students have a major misconception that mass determines whether an object floats or sinks. This is an activity that forces students to deal with that misconception and hopefully break it. The following materials are needed:
Have the students read the statement, "Objects that are high in mass, sink in water." Have the students show in some way if they agree with the statement, disagree with the statement, or are somewhat in between. Have them explain why they think that way and give examples. Then present the students with the list of all of the items to be placed into the tank, arranged according to their masses. Do not show the objects to the students. Have them write a hypothesis for each item (on whether they will sink or float) based only the property of mass. Then drop each item one by one, in order of their masses, into the water. Have students record the results. The students will realize that mass has nothing to do with whether an object sinks or floats. Then show the students the objects' densities. Hopefully they see the pattern of those objects with densities less than one float, and those with densities greater than one sink. It is not important to explain what density is at that point, but just that it is a property of matter that is vital in determining if an object floats or sinks.