Answers to End of Chapter Questions

1. Give two examples each of natural and of synthetic polymers. Answer: The size and mass of a polymer makes the name macromolecule seem reasonable, because the prefix macro – means large. Individual polymers may involve thousands of atoms, and molecular masses can reach over a million grams per mole. 3. Equation 9.1 contains an n on both sides of the equation. The one on the left is a coefficient; the one on the right is a subscript. Explain. Answer: The n on the left side of the equation gives the number of monomers that react to form the polymer. Thus, it is a coefficient. The n on the right side is a subscript; it represents the number of repeating units in the polymer. 4. In equation 9.1, explain the function of the over the arrow. Answer: The represents a free radical that initiates the polymerization. 5. Describe how each of these strategies would be expected to affect the properties of polyethylene. Also provide an explanation at the molecular level for each effect. a. increasing the length of the polymer chain b. aligning the polymer chains with one another c. increasing the degree of branching in the polymer chain Answer: a. At the molecular level, increasing the length of the polymer chain would increase its molar mass and the extent of its interactions with neighboring chains. This would be expected to somewhat increase the polymer's rigidity, strength, and melting point. b. At the molecular level, aligning polyethylene chains with one another means that the structure is more crystalline and highly ordered. This would be expected to give the polymer