Silly Putty (Hands-on)
Two solutions are mixed to make a substance similar to silly putty
Reference: “Chemical Magic from the Grocery Store,” by Andy S. W. Sae, Kendall/Hunt: Dubuque, 1996; p. 113.
In a cup or shallow pan, pour some Elmer’s glue.
Add to the glue a 4% borax solution (7.6 g sodium tetraborate / 100 mL water).
Stir the glue to expose all the glue to the solution.
Squeeze out any bubbles of sticky glue that may form.
Explanation: Glue is a sticky mass of polymer chains. The borax solution cross-links these polymers and occupies the sticky parts of the polymer. This connects the polymers together so they don’t slide against each other as much.
Tips:
Reference: “Chemical Demonstrations, Volume 3,” by Bassam Z. Shakhashiri, University of Wisconsin Press: Madison, 1989; p. 362.
“Chemical Demonstrations, Volume 2,” by Lee R. Summerlin, Christie L. Borgford and Julie B. Ealy, Second Edition, American Chemical Society: Washington, 1988; p. 97.
“Chemical Activities,” by Christie L. Borgford and Lee R. Summerlin, Teacher Edition, American Chemical Society: Washington, 1988; p. 87.
Pour 50 mL of water into a 250-mL beaker.
Heat on a hot plate to just below boiling (<90 degrees Celsius).
While stirring, slowly add 2 grams of polyvinyl alcohol.
While stirring vigorously with a rod or stick, add 5 mL of a 4% borax solution (7.6 g sodium tetraborate / 100 mL water).
Allow the solution to cool and pick it up, using your hands, out of the beaker.
Explanation: The borax cross-links the polyvinyl alcohol chains through hydrogen bonding. This allows the solution to flow slowly by breaking and reforming these bonds. If too much force is used the bonds will break and not reform.
Tips:
Two solutions are mixed to make a pink polymer.
Reference: “Chemical Demonstrations, Volume 1,” by Bassam Z. Shakhashiri, University of Wisconsin Press: Madison, 1983; p. 219.
Perform this demonstration in a hood or well-ventilated area.
Pour 25 mL of 12M formaldehyde (Formalin, 37%) to a 250-ml beaker.
Add 55 ml of glacial acetic acid and 20 grams of phenol.
Mix the solution well and quickly add 55 ml of concentrated HCl while stirring.
After a minute the solution will turn pink and solidify.
Explanation: This reaction forms a resin polymer. There exists network of branches within the polymer instead of linear chains.
Tips:
Water is added to cornstarch to make an interesting solution.
Reference: “Chemical Demonstrations, Volume 3,” by Bassam Z. Shakhashiri, University of Wisconsin Press: Madison, 1989; p. 364.
Pour some cornstarch into a shallow pan.
Slowly add water while mixing.
Observe how the properties of the solution change while adding more water.
Use about half a cup of cornstarch for every 50 ml of water as a guide.
When you press down on it, it feels like a solid, but you can pour it like a liquid.
Explanation: This solution is called a dilatant substance. As the rate of shear increases the resistance to flow increases. When you apply a strong force to the substance like stirring, it resists movement, but it freely moves on its own by gravity.
Tips:
A styrofoam cup is placed in a clear liquid and gradually disappears.
Reference: “Chemical Magic from the Grocery Store,” by Andy S. W. Sae, Kendall/Hunt: Dubuque, 1996; p. 117.
Procedure: Pour some acetone into a very shallow dish or clear beaker.
Place a Styrofoam cup in the pan.
Observe what happens.
Explanation: The acetone appears to be dissolving the cup. The acetone is actually rearranging the polystyrene chains and removing the air trapped in the foam.
Tips: