Discrepant Events: Mysterious Floating Cork

Posted by David Wetzel

Discrepant Events

Discrepant events are one form of minds-on thinking designed to help students focus on their prior conceptions of about the world in which they live.

This step is necessary if students are to alter their conceptions and internalize accepted scientific views.

This discrepant event provides concrete evidence of the Meniscus effect of liquids in containers, along with surface tension.

Materials:

one clear glass, one small cork, and tap water.

Procedures:

1. Students fill glass two thirds full of water
2. They now place the cork in the glass of water and try to keep it floating in the center
3. Ask students if they can keep the cork in the middle and explain what they are observing
4. Students observe the cork always moves to the edge of the glass (answer: cork moves to highest water level because the cork is less dense than water - meniscus effect)
5. Ask students what they think will happen to the cork if the class is filled with water
6. After discussion, students now add water to the glass so that it creates a bubble of water on top the glass, without overflowing (cork is still in glass)
7. Students now observe the cork moves to the center of the glass (answer: the cork moves to the highest point because it is less dense than water and the cork is held in place due to surface tension)

The use of discrepant events is the best way to motivate the unmotivated student and engage all students in critical thinking.

The use of the materials above are typically within the realm of most students’ personal experiences and knowledge, which makes the mental conflict and resulting better understanding of related science concepts more meaningful for them.

Related Resources:

Discrepant Events and Critical Thinking

More Discrepant Events in Science