Are you looking for a science fair idea?
Explore these sites to find a project.
http://www.youth.net/nsrc/webs.html
http://school.discovery.com/sciencefaircentral/
reachoutmichigan.org/funexperiments/quick/earlyelem.html
reachoutmichigan.org/funexperiments/quick/middlesch.html
http://www.sciencefair-projects.org
www.weatherwizkids.com/WxExperiments.htm