Reaction in a Bag – Making Silly Putty Purpose: To engage students in a hands-on activity that allows them to DO a chemical reaction that has many exciting aspects! Theory: Chemical reactions involve changing reactants (what you start off with) into products (the resulting chemicals). This is done by breaking and forming chemical bonds between atoms. Chemical reactions are different than phase changes, which are a physical change of phase; the same substance at the beginning is present after the change. Students can tell a chemical reaction has occurred if one or more of the following are observed: Colour change Gas produced (might smell the gas) Physical change **Important for the silly putty reaction Temperature change (other than adding heat to the reaction) o Two “big words” students can learn is that an exothermic reaction gives off heat (feels hot) and an endothermic reaction takes in heat (feels cool) Give every day examples of chemical reactions so students can see this does apply to their lives. Common ones are baking (a cake for example, with reactants of flour, sugar, eggs, chocolate and product a cake) or the reaction of baking soda and vinegar to make carbon dioxide bubbles. For silly putty the borax causes molecules in the glue (which is a polymer) to become cross-linked, making the glue more solid than liquid. Materials needed: To make one golf ball size batch of slime you will need: Elmer's glue (most kinds of white craft glue will work) cups or beakers or Ziploc bags Food coloring (you pick the color) Water Borax (available at most large grocery stores near the laundry detergent) A plastic spoon (for stirring) A tablespoon (for measuring) What to do beforehand: - Mix about a teaspoon of the Borax into a cup of water and stir (it usually doesn't fully dissolve) Make a ½ and ½ glue solution (1/2 glue, ½ water) SLIME TIME! 1. 2. 3. 4. Put about 1/2 inch of glue into a beaker or Ziploc Add a few drops of food coloring and stir (or squish to mix if using bags) Add one tablespoon of the Borax solution and stir well. Lift out the spoon with the goo and play with it! It will be messy! **You can play with the ratio of glue: borax to see what works best A Catalyst 2011 legacy resource