A substance made up of two or more elements is called a compound.

Here are some key points about compounds:

* Chemically bonded: The elements in a compound are chemically bonded together in a fixed ratio.

* New properties: Compounds have properties that are different from the elements that make them up. For example, water (H₂O) is a liquid at room temperature, while hydrogen and oxygen are both gases.

* Cannot be separated by physical means: Compounds can only be broken down into their constituent elements by chemical reactions.

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