>Where did the chemicals come from?

they came from the heavy elements created in the cores of stars via nucleosynthesis (and blown out into space when those stars exploded into supernovas), which came from interstellar nebula of hydrogen and helium, which came from matter produced from energy which was created by an inflationary false vacuum emerging out of a quantum vacuum fluctuation at the beginning of the universe.

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"Study your math, kids. Key to the Universe." - the Archangel Gabriel, 'The Prophecy'