A polymer is a very long chain-like molecule. Poly means many and mer means unit. A polymer is made by bonding (linking together) many small molecules called monomers (one unit). Polymers can be made of kinds of monomers and they can be linked together in different ways.
A model of a polymer, such as the one shown in the diagram, can be made using modeling clay and pipe cleaner pieces. Let each ball of clay represent one monomer. Use clay balls that are similar in size, shape, and color. The bonds, represented by pieces of pipe cleaner must also be as identical as possible. This includes color and length.
Plastic storage bags, such as sandwich bags, are made polyethylene, which is a polymer. Ethylene is the monomer. The physical organization of the polyethylene in a plastic bag is much like a ball of fuzzy yarn with fibers intertwined and sticking out in all directions. Because of this structure, if a plastic bag is punctured with a pencil, the polyethylene molecules move out-of-the-way, but the entangles molecules form a seal around the pencil. It appears to be magic, but it is really all about science.
Discover For Yourself
1. Fill a quart-size plastic resealable bag about three-fourths’ full with water.
2. Hold the bag over a tray or any container that would hold the water if there is a spill.
3. Push the pointed end of a pencil through one side of the bag and out the other side.
As long as the pencil remains in place, the bag will not leak.
4. Remove the pencil.
Removing the pencil shows that the hole left by the pencil appears stretched around the edges, but not torn. The hole is slightly smaller in diameter than that of the pencil. Water is able to stream out of this hole.