Q. Arrange the following polymers in increasing order of their density:

1. Polypropylene
2. Polyethylene (HDPE form)
3. PTFE

Which of the following is the correct sequence?
Answer: 1 < 2 < 3
Notes: Polypropylene has the lowest density (approximately 0.90 g/cm³), followed by high-density polyethylene (HDPE, about 0.95 g/cm³), while PTFE (polytetrafluoroethylene) has the highest density (around 2.2 g/cm³). Therefore, the correct increasing order is: Polypropylene < Polyethylene (HDPE) < PTFE.