ELI5: How is plastic made from petroleum?

Plastic is made by taking dark, gooey oil from deep underground, breaking it down into tiny chemical pieces, and linking those pieces back together like toy building blocks to form everyday objects.

Think of crude oil (petroleum) as a big bucket full of mixed-up Lego bricks of all shapes and sizes. To make a plastic toy, a water bottle, or a grocery bag, scientists follow a few simple steps:

• Sorting the pieces: The oil is heated up in a giant tower. This process separates the heavy, thick parts from the light, airy parts.
• Cracking the blocks: Scientists take a specific light liquid from the oil and "crack" it with super-high heat. This chops large chemical chains into very tiny, identical pieces called monomers. Think of this like separating all your snap-together beads so they are ready to use.
• Snapping them together: Next, heat and a special helper ingredient cause thousands of these tiny beads to click together into super-long, strong chains called polymers.
• Melting and shaping: These long chains come out looking like tiny plastic grains or squishy noodles. Factories melt these noodles down and pour them into molds, puff them up like balloons, or squeeze them out flat.