Substance:
* Definition: A pure form of matter with a fixed and definite composition.
* Characteristics:
* Has a uniform composition throughout.
* Cannot be separated by physical means (like filtration or evaporation).
* Has a fixed set of properties like melting point, boiling point, and density.
* Examples:
* Water (H₂O): Always composed of two hydrogen atoms and one oxygen atom in a fixed ratio.
* Gold (Au): Pure gold is an element and has a consistent atomic structure.
Mixture:
* Definition: A combination of two or more substances that are not chemically bonded.
* Characteristics:
* Can have a variable composition.
* Can be separated by physical means.
* Properties are a blend of the individual substances.
* Examples:
* Saltwater: A mixture of salt (NaCl) and water (H₂O), which can be separated by evaporation.
* Air: A mixture of gases like nitrogen, oxygen, carbon dioxide, and others. The proportions of these gases can vary slightly.
