Which of the following polymers soften on heating and harden on colling? What are the polyfmers with this property collectively called ? What are the structural similarites between such polymers? Bakelite urea formaldehyde resin , polythene, polyvinyls, polystyrene.

Explanation

To solve the question, we will follow these steps:

### Step 1: Identify the Properties of Each Polymer
We need to analyze the given polymers: Bakelite, Urea Formaldehyde Resin, Polythene, Polyvinyl, and Polystyrene, to determine which ones soften on heating and harden on cooling.

### Step 2: Classify the Polymers
From our analysis:
- **Polythene**: Softens on heating and hardens on cooling.
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