SCH4C                    Lab #8 - Making a Super Ball
Introduction:  Two common liquids are mixed, and the reaction makes a solid that has properties of rubber.  The solid is a polymer.  Chemists identify polymers as long chains in which molecules have linked up and twisted around each other, much like the paper chains people make for Christmas trees.  Nylon, polyethylene, wood (cellulose), proteins, and most plastics and rubbers are all polymers of particular molecules.

Materials: 20 mL sodium silicate (water glass solution),  5-10 mL ethyl alcohol, Stir stick, paper towels, paper cup for mixing of solution.

Safety Note:  Students should wear goggles and plastic disposable gloves

1     Measure 20 mL of sodium silicate solution and pour it into a small paper cup.  Avoid contact with your skin.
2. Place 5 mL of ethyl alcohol in another paper cup.  Alcohol is flammable.  Extinguish all flames in the room.
3. Add the alcohol to the sodium silicate solution.
4. Using a circular motion, stir with the stick until the substance formed is solid.
5. Place the polymer in the palm of your hand and gently press with the palm of the other hand until a spherical ball that no longer crumbles is formed.  Be patient.  Discover a technique.  Moisten the ball occasionally by holding it in a small stream of water from the faucet.
6. Bounce your ball!  Gently at first.  Don't let it get away from you.
7. Investigate as many property differences as you can between the two  liquids and the solid polymer bouncy ball.  Check the acid-base nature of each of the substance, as well as solubility and density.

Reaction:   Silicon is a very interesting type of atom.   Find its position on the periodic table of the elements.  Like carbon, silicon makes four chemical bonds and can branch out in that many directions to make long chains.  In sodium silicate, the silicon atom is bonded to 4 oxygen atoms and is not linked in any chains.  The ethyl alcohol molecule is very simple and has just two carbon atoms.  When sodium silicate and ethyl alcohol are put together, the silicate particles begin to link  up with each other to form long chains as the ethyl groups (sometimes shown as "R") replace oxygen atoms in the silicate ion.  Some become cross-linked between chains.  Water molecules are by-products of the formation of the polymerization bond.
    The large molecule is a solid.  It is a type of silicone polymer:

1.    How did you know that a chemical reaction had taken place when the two liquids were mixed?
2.    How could you find out what liquid was pressed out of the mass of crumbled solid as you formed the ball?
3.    Compare your ball with those of the other members of the class.  How many properties can you compare (e.g. diameter of sphere versus height of bounce)?  List and compare them.