* Multiple components: Seawater is composed of water (H2O), dissolved salts (mainly sodium chloride, but also magnesium, potassium, calcium, and others), dissolved gases (oxygen, nitrogen, carbon dioxide), and even small amounts of organic matter.
* No fixed composition: The proportions of these components can vary depending on location, depth, and other factors. For example, the salinity (salt content) of seawater is higher in some regions than others.
* Separable components: The components of seawater can be separated by physical means. For instance, salt can be extracted by evaporation, and fresh water can be obtained through desalination processes.
In contrast, a pure substance has a fixed composition and cannot be broken down into simpler substances by physical means. Examples of pure substances include water (H2O), gold (Au), and oxygen (O2).
Therefore, because seawater is a combination of multiple components with varying proportions that can be physically separated, it is classified as a mixture, not a pure substance.
