If you like us, please share us on social media.
The latest UCD Hyperlibrary newsletter is now complete, check it out.

GeoWiki.png
ChemWiki: The Dynamic Chemistry E-textbook > Development Details > Approaches > Demos > Additional Demos > The States of Matter-- Starch Solution: Solid or Liquid?

MindTouch
Copyright (c) 2006-2014 MindTouch Inc.
http://mindtouch.com

This file and accompanying files are licensed under the MindTouch Master Subscription Agreement (MSA).

At any time, you shall not, directly or indirectly: (i) sublicense, resell, rent, lease, distribute, market, commercialize or otherwise transfer rights or usage to: (a) the Software, (b) any modified version or derivative work of the Software created by you or for you, or (c) MindTouch Open Source (which includes all non-supported versions of MindTouch-developed software), for any purpose including timesharing or service bureau purposes; (ii) remove or alter any copyright, trademark or proprietary notice in the Software; (iii) transfer, use or export the Software in violation of any applicable laws or regulations of any government or governmental agency; (iv) use or run on any of your hardware, or have deployed for use, any production version of MindTouch Open Source; (v) use any of the Support Services, Error corrections, Updates or Upgrades, for the MindTouch Open Source software or for any Server for which Support Services are not then purchased as provided hereunder; or (vi) reverse engineer, decompile or modify any encrypted or encoded portion of the Software.

A complete copy of the MSA is available at http://www.mindtouch.com/msa

The States of Matter-- Starch Solution: Solid or Liquid?

 

Chemical Concept Demonstrated

  • The difficulty in classifying a substance as a liquid or a solid

Demonstration

Through a variety of different procedures, determine whether the corn starch and water solution that the beaker contains is a solid or a liquid. For example:

  • Hit the surface with a stirring rod.
  • Set the end of the rod on the surface.
  • Scratch the surface.
  • Stir the solution.
  • Submerge a finger in the starch solution.
  • Try to yank it out.
  • Feel it with your palm.
  • Now, feel it between the forefinger and thumb.
  • Drop some into your hand.
  • Drop some onto the bench.
  • Pick up the puddle.
  • Like a solid
  • It will sink
  • It will crack.
  • Like a liquid
  • It will sink.
  • Pulling needed
  • It feels wet and forms a puddle.
  • It feels like a powder.
  • It can break into pieces.
  • It forms a puddle.
  • Like a solid


Explanation

When pressure is applied to this solution, it exhibits the properties of a solid.   When the pressure is released, it exhibits the properties of a liquid. The starch granules reversibly absorb and release water depending upon the external pressure applied.  Because the mixture should look like a liquid when properly made, the confusion over whether or not to call it a solid or liquid is only amplified.

It should be noted that creating this ambiguous solution can be rather tricky.  Adding too little cornstarch will provide the properties of a liquid, and adding too much will provide the properties of a solid.  The middle ground is difficult to obtain, so care should be taken during the preparation.

This demonstration has been used in the past to make students realize that some solids and liquids are difficult to classify as one or the other.

Contributors

 

You must to post a comment.
Last Modified
10:31, 2 Oct 2013

Tags

Classifications

(not set)
(not set)

Creative Commons License Unless otherwise noted, content in the UC Davis ChemWiki is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License. Permissions beyond the scope of this license may be available at copyright@ucdavis.edu. Questions and concerns can be directed toward Prof. Delmar Larsen (dlarsen@ucdavis.edu), Founder and Director. Terms of Use