Question

bend and stretch = structure and function of designed materials
student answer packet 2: to be completed individually.
bond energy is the energy required to break one mole of the designated bonds in the gaseous state. although each molecule has characteristic bond energies, generalizations can be made concerning the energy to break bonds in molecules and the stability or reactivity of molecules, even in nongaseous states.
figure 4: average bond energies

1. the polymer ldpe (plastic #4) has a structure similar to ptfe, but is unsuitable for use with acetone. cite evidence and provide reasoning to support the observed chemical stability of ptfe compared to the chemical reactivity of ldpe.

evidence:
reasoning:

Explanation:

• Evidence: From the bond energy table, the C-F bond (485 kJ/mole) has a much higher bond energy than the C-H bond (413 kJ/mole) present in LDPE.
• Reasoning: Higher bond energy means more energy is required to break the bond. PTFE's structure is dominated by strong C-F bonds, which resist breaking when exposed to acetone. LDPE's C-H bonds are weaker, so they are more easily broken by acetone, leading to reactivity and making LDPE unsuitable for use with acetone.

Answer:

Evidence: The C-F bond (485 kJ/mole) has higher bond energy than the C-H bond (413 kJ/mole).
Reasoning: Stronger C-F bonds in PTFE require more energy to break, so PTFE is stable to acetone. Weaker C-H bonds in LDPE break more easily, making LDPE reactive with acetone.