The difference in the densities of low density polymer (LDP) and high density polymers (HDP) is due to the fact that

Options

A. a. LDP are highly branched structures while HDP consists of closely packed linear molecules
B. b. LDP are linear chains while HDP are branched chains of polythene
C. c. both LDP and HDP are unbranched linear chains with different lengths
D. d. at high temperature , the density of polymer is reduced .

Answer

To solve the question regarding the difference in densities between low density polymers (LDP) and high density polymers (HDP), we need to analyze the structural characteristics of both types of polymers and how these characteristics influence their densities.

### Step-by-Step Solution:

1. **Understanding Low Density Polymers (LDP)**:
- LDPs are produced by the polymerization of ethene under high pressure (1000 to 2000 atm) and high temperatures (350 to 570 Kelvin) in the presence of oxygen or peroxide initiators.
- The polymerization process results in highly branched structures. These branches prevent the molecules from packing closely together, leading to lower density.

2. **Understanding High Density Polymers (HDP)**:
- HDPs are formed by polymerizing ethene using a hydrocarbon solvent like Triethyl Aluminium and TiCl4 at lower pressures (6 to 7 atm) and moderate temperatures (333 to 343 Kelvin).
- The polymerization results in linear chains that can pack closely together, which increases the density of the material.

3. **Comparing Structures and Densities**:
- The key difference in density arises from the molecular structure: LDPs have branched structures, while HDPs consist of linear chains.
- The branched structure of LDPs leads to less efficient packing, resulting in lower density compared to the closely packed linear chains of HDPs.

4. **Evaluating the Options**:
- **Option A**: "LDP are highly branched while HDP consists of closely packed linear molecules." - This is correct and explains the density difference.
- **Option B**: "LDP are linear chains while HDP are branched chains." - This is incorrect; LDPs are branched, not linear.
- **Option C**: "Both LDP and HDP are unbranched linear chains with different lengths." - This is incorrect; LDPs are branched.
- **Option D**: "At high temperature the density of polymer is reduced." - While this is true, it does not directly explain the difference in densities between LDP and HDP.

5. **Conclusion**:
- The correct answer is **Option A**: The difference in densities of low density polymer (LDP) and high density polymers (HDP) is due to the fact that LDP are highly branched while HDP consists of closely packed linear molecules.