Clear plastic wrap. Tupperware containers. Scotch tape. Swimsuits. Are all of these things plastic in different forms? What is the unifying chemical structure common to all these different things that makes them all plastic?
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Other people are explaining what carbon based polymers are, which is brilliant, but miss one important bit:
Why are some things plastics, some rubbers (elastomers), and some gel or liquid, despite all being carbon based polymers.
And the difference is… Well, exactly what it seems. The consistency. Polymers can exist in most of these states depending on temperature. Rubbers become rigid and crack when cooled. Plastics soften and stretchy when heated. Polymers that aren’t crosslinked (like vulcanised rubber is) can melt.
The only difference really is what properties the specific polymers have in the “human” temperature range, or the one they’re meant to otherwise operate in. Plastics are hard and stiff in “our” temperatures, that’s honestly the only definition (Of course it can get complicated real fast with some edge cases). Rule of thumb, jf it’s a polymer but is isn’t stretchy or runny at room temperature, it’s a plastic.
In technical terms, there’s a thing called “glass-rubber transition temperature”, most polymers have one. Rubber is obviously rubber, “glass” is what we commonly call plastic. It’s called that because it’s solid, stiff and brittle but not a crystal, so the technical definition of “glass”. So we divide things into “rubbers” and “plastics” roughly based on whether the glass transition temperature is above or below about 0-30C.
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