1. Fixed Composition:
* Compounds: Have a fixed and definite ratio of elements. Water always contains two hydrogen atoms and one oxygen atom per molecule (H₂O). This ratio never changes.
* Mixtures: Can have varying compositions. For example, saltwater can have different amounts of salt dissolved in water.
2. Chemical Bonding:
* Compounds: Formed by chemical bonds between atoms. In water, hydrogen and oxygen atoms share electrons, forming a strong covalent bond.
* Mixtures: No chemical bonds form between components. In saltwater, the salt crystals are simply dissolved in the water, not chemically combined.
3. Properties:
* Compounds: Have unique properties different from their constituent elements. Water is a liquid at room temperature, while hydrogen is a gas and oxygen is a gas.
* Mixtures: Retain the properties of their individual components. Saltwater still tastes salty because it contains salt, and it's still liquid because it contains water.
4. Separation:
* Compounds: Can only be separated by chemical reactions, breaking the bonds. Electrolysis can separate water into hydrogen and oxygen gas.
* Mixtures: Can be separated by physical means, such as evaporation, filtration, or distillation. Saltwater can be separated by evaporation, leaving behind the salt.
5. Homogeneity:
* Compounds: Are homogeneous, meaning they have a uniform composition throughout. Water is the same throughout its entire volume.
* Mixtures: Can be homogeneous (like saltwater) or heterogeneous (like sand and water).
In summary, water's fixed composition, chemical bonding, unique properties, requirement of chemical methods for separation, and homogeneity all point to it being a compound, not a mixture.
