What characteristic defines plastics?

The defining characteristic of plastics is their high molecular weight and formability. Plastics are polymers made up of long chains of repeating molecular units, which gives them their high molecular weight. This structural property is essential as it creates the necessary physical characteristics that allow plastics to be molded, shaped, and formed into various products. Their formability means they can easily be processed and engineered into a wide range of products, from containers to automotive parts, making them versatile materials in manufacturing.

Plastics are typically not characterized primarily by their low molecular weight, which does not apply to most conventional plastics. While some plastics may have the ability to burn easily, this is not a universal trait and varies depending on the specific type of plastic and its formulation. Lastly, while certain plastics can offer electrical resistance, this is more of a functional attribute rather than a defining characteristic of all plastics. Thus, the correct answer captures the essence of what defines plastics as materials used across various industries.