Interesting online CONFCHEM discussion going on right now on the ChemWiki and
greater STEMWiki Hyperlibary project. Come join the discussion.

ChemWiki: The Dynamic Chemistry Hypertext > Under Construction > Demonstrations > Additional Demos > Smart Balls/ Stupid Balls

Smart Balls/ Stupid Balls

Chemical Concepts Demonstrated

  • Copolymerization
  • Cross-linking


These two (apparently) similar balls are bounced. balls.gif


One ball bounces significantly higher than the other.


The "hard" (smart) ball is made up of polybutadiene to which an unusually large amount of sulfer has been added (up to 15 parts of sulfur per 100 parts of polybutadiene).  There is extensive cross-linking involved in this polymer, so it dissipates very little energy in the form of heat when it bounces.

The "soft" (stupid) ball is a block co-polymer, such as poly(styrene-butadiene) or poly(vinyl-butadiene).  It has very little significant resiliance.   It should be noted that poly(styrene-butadiene) is used for automobile tires, which absorb some of the energy associated with the bumps along the highway.



You must to post a comment.
Last modified
10:29, 2 Oct 2013



(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 Questions and concerns can be directed toward Prof. Delmar Larsen (, Founder and Director. Terms of Use