We just started to learn about Making Oil, which is also called petroleum.
One part of making oil is Crude Oil.
Before oil can be used in car engines or used to make things like plastics, it has to be cleaned up.
Almost like drinking water from a river might have a bunch of dirty things in it, oil can be the same way.
Crude oil means oil that is just found underground, and has to be cleaned up.
Sometimes it is floating above some water and below some gas, and doesn't need much cleaning.
Other times it is mixed up with sand and has to be filtered out. This is called bitumen or asphalt.
Other times it is thick almost like jelly and has to be made into more of a liquid. This is called heavy oil.
(from: wikipedia - petroleum)
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