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Floating Squares

Deanna Cullen's picture
Tue, 06/03/2014 - 13:00 -- Deanna Cullen
floating squares

I was looking for a new demonstration to initiate a discussion about polarity and related properties to use as part of an exam review. I found a video at ChemEd X (this is part of a ChemEd X subscription). It is entitled “Floating Squares – Hexane and Water” (see note below). I have placed both solutions together before, but I had not added the squares. The demonstration fulfilled my needs. I could have used the original video and muted it if I had not had hexane to demonstrate with.

I also tried the demonstration with mineral oil in place of the hexane with good results. The only thing I missed there without using hexane is that I hadn’t told my students which layer was water and which was the hexane. I placed a drop of water on the counter then took a drop of liquid from the top layer of the beaker. The hexane evaporates quickly while the water drop is still present. This allowed a discussion to confirm that the top layer was hexane and the bottom was water. Of course, the concept of density should come up in conversation also. We also discussed “why” the hexane evaporates so much faster than the water does. Using the mineral oil left that part of the discussion lacking.

I poured my hexane/water in a jar along with the pieces of paper and was able to mix the solution allowing the students to see that the paper squares always turn graphite up (gravitating toward the hexane) without exposing us to the evaporating hexane.

The original video credits:

Design and Demonstration - David Whisnant, Wofford College, Spartanburg SC 29303

Video - Jerrold J. Jacobsen, University of Wisconsin - Madison, Madison, WI 53706

Text - David Whisnant, Wofford College, Spartanburg SC 29303 & Jerrold J. Jacobsen, University of Wisconsin - Madison, Madison, WI 53706

Chemistry Topic: 
Chemical compound: 

Comments

Tom Kuntzleman's picture
Submitted by Tom Kuntzleman on

I love this experiment.  It is so simple, yet so effective.  Thanks for sharing it with us. 

Tom Kuntzleman

Dana Griffiths's picture
Submitted by Dana Griffiths on

I am not sure why, but this video won't load for me. I can see the opening picture, and three oscillating "dots" showing me that it trying to load, but nothing happens after that.  :(

I will try again later, I guess.

Deanna Cullen's picture
Submitted by Deanna Cullen on

It is loading for me using Internet Explorer and Safari. Let me know what browser you are using if it still isn't working for you. :)

Deanna Cullen

Whitehall High School, MI

@CullenChemEdX 

Dana Griffiths's picture
Submitted by Dana Griffiths on

Let me clarify: the videos embedded on this page do work perfectly. When I first attempted, I clicked on the video linked to the original ChemEd video in your blog that I got through email (the embedded videos weren't visable in that format). It is the ChemEd video I can't get to work. But returning to this page, and seeing the embedded videos, I tried them out and they worked perfectly.

Deanna Cullen's picture
Submitted by Deanna Cullen on

I am glad it is working for you. Some may be confused about the original video. You do need a ChemEd X subscription to view that one (as noted). This original is only 21 seconds long and doesn't include any information that can't be found in mine. The embedded videos that I included do tend to work better than the associated links. I hope you found them valuable. 

Deanna Cullen

Whitehall High School, MI

@CullenChemEdX