A substance that can be split up into simpler substances is called a compound.

Here's why:

* Elements are the simplest pure substances that cannot be broken down further by chemical means. Examples include oxygen (O), carbon (C), and gold (Au).

* Compounds are formed when two or more elements chemically combine in a fixed ratio. They can be broken down into their constituent elements through chemical reactions. Examples include water (H₂O), table salt (NaCl), and sugar (C₁₂H₂₂O₁₁).

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