What are high and low density polythenes ?

Explanation

### Step-by-Step Solution:

**Step 1: Definition of Polyethylene**
Polyethylene is a polymer made from the polymerization of ethylene monomers. It is one of the most commonly used plastics and can be categorized into different types based on its density and structure.

**Step 2: High-Density Polyethylene (HDPE)**
- **Structure**: HDPE has a linear structure with minimal branching. This structure allows the polymer chains to pack closely together.
- **Density**: Due to its linear structure, HDPE has a higher density, typically around 0.95 g/cm³ or more.
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