10. Explain why laboratory identification of a plastic so often involves burning the plastic.

11. Explain the flammability of aromatic versus aliphatic molecules from an energy perspective, assuming the bond strength of a C-C bond is approximately twice as much as the bond strength of a C-C and also that the bond strength of a hydrogen at- tached to benzene is about 20% higher than the bond strength of hydrogen attached to propylene.

12. Low-density polyethylene is normally translucent. If a piece of this material is bent into a tight radius, it translates less light (becomes chalky white). What is this phe- nomenon called? Explain why this happens. Explain why the material often breaks after repeated bends.