Define 'thermoplastics' and give an example.

Thermoplastics are defined as materials that can be repeatedly softened by heating and hardened by cooling. This property allows thermoplastics to be molded or shaped into various forms during the heating process, making them versatile for a wide range of applications. Upon cooling, they solidify, retaining the new shape until they are reheated. An example of a thermoplastic is polyethylene, which is widely used in packaging, bottles, and containers due to its lightweight and durable properties.

The provided answer accurately describes thermoplastics by emphasizing their ability to undergo reversible changes in state with temperature. Polyethylene is indeed a correct instance of a thermoplastic, showcasing its practical applications in everyday products.