On the NET…
Some web sites that you might find helpful….

Significant Figure Web Sites Rules and Examples
http://dbhs.wvusd.k12.ca.us/SigFigs/SigFigs.html
http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch1/sigfigs.html
http://www.umd.umich.edu/casl/natsci/slc/slconline/SIGF/page7.html (includes diagrams of tools) 
http://www.chem.ufl.edu/~chm2040/Notes/Chapter_1/figures.html (more diagrams)
http://www.swt.edu/slac/math/SigFigur.html
http://www.chem.tamu.edu/class/majors/commonfiles/sigfig.htm

 Practice for Significant figures (Computer applets)
http://science.widener.edu/svb/tutorial/sigfigures.html
http://lectureonline.cl.msu.edu/~mmp/applist/sigfig/sig.htm  

Tutorial Illustrating the Use of Significant Figures
http://www.chem.sc.edu/faculty/morgan/sigfigs/

 Metric System
Various prefixes and applications of the metric system in chemistry
http://dbhs.wvusd.k12.ca.us/Metric/Metric.html
http://members.aol.com/profchm/metric.html
http://www.chemistrycoach.com/math_skills_for_chemistry_tutori.htm#Math Skills for Chemistry Tutorials

Chemical and Physical Change
Quizzes
http://www.1001-periodic-table-quiz-questions.com/quiz/k-12/change_1.html
http://qldscienceteachers.tripod.com/junior/quizzes/chem_changes.html

Differences between Chemical and Physical Changes
http://dbhs.wvusd.k12.ca.us/Matter/2.4bPhysicalChemChanges.html
http://nobel.scas.bcit.ca/chem0010/unit2/2.3_changes.htm#

Melting Freezing
Discussion of Melting and Freezing Characteristics
http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch14/melting.html#melt

Using Density  Visualization of Density
http://www.nyu.edu/pages/mathmol/textbook/density.html