Nothing Screams Discrepant Event Like a Floating Cannonball!

Dec 15, 2011 by

The science teacher in me knows what’s going to happen in the video above before the cannonball is dropped into a vat of the silvery liquid metal, but the curious learner in me still squeals with delight when the cannonball actually floats!

I’m a HUGE fan of trying to provide discrepant events for my students, whether it’s science based or not, and while I also advocate that it’s best to have a live demonstration of some phenomenon that challenges learners to question what they may already know about simple concepts, there are times when a live demonstration isn’t practical. In this case, students may think, “wow, a vat of liquid, I know that heavy things like metal tend to sink in liquids”. They’re then hit with the starting revelation that some liquids are in fact so dense that even something as heavy as a cannonball can float, which begins to generate questions almost without fail, “what else could float in mercury that can’t in water? what else will make a cannonball float? how dangerous is a vat of mercury like that?”

On a simliar chord, here’s a “magical” anti-gravity machine made out of nothing but a copper tube!

Rather than ramble on about providing discrepant events, and hitting you with dozens of more examples, I have a challenge for you today.

I challenge you to share one piece of video that allows you to challenge your students’ pre-conceived notions or understandings of a topic as a way to engage them at the beginning of a unit or lesson. All subject areas are welcome!

Comments are always welcome, but simply sharing with a colleague is great too!

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