In short
An element has only one kind of atom. A compound has two or more elements chemically joined in a fixed ratio. A mixture has substances that are not chemically joined and can be in any ratio.
Elements, such as iron and oxygen, cannot be broken down by chemical reactions. A compound, such as water, has properties different from its elements and can be separated only by a chemical reaction. The parts of a mixture, such as air or sea water, keep their own properties and can be separated by physical methods such as filtering, distilling or evaporating. Steam is a compound, because it is water in the gas state.
Iron and sulfur powders stirred together are a mixture: a magnet takes out the iron. Heated together, they make iron sulfide, a compound that the magnet no longer separates.
Also searched as: is steam a compound.
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