What is a compound?

A compound is defined as two or more elements that are chemically combined in a fixed ratio. This means that the individual elements undergo a chemical reaction to form a new substance, which has properties distinct from the original elements. For example, when hydrogen combines with oxygen in a specific ratio, it forms water (H2O), which exhibits entirely different characteristics than hydrogen or oxygen alone. Compounds have a uniform composition throughout and can only be separated into their constituent elements through chemical reactions, distinguishing them from mixtures, which can involve various substances without any chemical bond. Understanding this concept is fundamental in chemistry, as it lays the groundwork for more complex topics, including chemical reactions and the behavior of substances in different environments.