1. Strong Van der Waals Forces: Polyethylene molecules are held together by van der Waals forces, specifically London dispersion forces. These forces arise from temporary fluctuations in electron distribution within the molecule, creating temporary dipoles that induce dipoles in neighboring molecules. The long, linear chains of polyethylene allow for extensive intermolecular contact, leading to strong van der Waals forces.

2. High Molecular Weight: Polyethylene has a high molecular weight, meaning its chains are long. These long chains can entangle and interact with each other over a large surface area, further strengthening the van der Waals forces.

3. Crystalline Structure: Polyethylene can have a highly crystalline structure, where the molecules are arranged in a regular, ordered manner. This order allows for closer packing of the molecules, leading to stronger intermolecular forces.

4. Absence of Polar Groups: Polyethylene is non-polar, meaning it lacks any polar groups like hydroxyl (-OH) or carbonyl (C=O) groups. The absence of polar groups minimizes any potential dipole-dipole interactions, contributing to the dominance of the van der Waals forces.

5. Flexibility and Chain Entanglement: While polyethylene chains are flexible, they can still entangle with each other. This entanglement adds to the overall strength of the solid structure and contributes to its high melting point.

In summary: The combination of strong van der Waals forces due to its high molecular weight, long chain length, and crystalline structure makes polyethylene a high melting solid.