Matter is primarily classified into two broad categories: pure substances and mixtures.
Pure Substances
Pure substances have a fixed composition and distinct properties. This means their makeup is consistent throughout, and their characteristics (like melting point or boiling point) are always the same under the same conditions. Pure substances can be further broken down into:
- Elements: These are substances that cannot be broken down into simpler substances by chemical means. They consist of only one type of atom. Examples include gold (Au), oxygen (O), and nitrogen (N).
- Compounds: These are substances composed of two or more different elements chemically bonded together in a fixed ratio. They can be broken down into simpler substances (elements) by chemical reactions. Examples include water (H₂O), sodium chloride (NaCl), and carbon dioxide (CO₂).
Mixtures
Mixtures are physical combinations of two or more substances (elements and/or compounds) where each substance retains its own chemical identity. They can be separated by physical means. Mixtures can be categorized as:
- Homogeneous Mixtures: These mixtures have a uniform composition throughout. The different components are evenly distributed, and you cannot see the individual substances. A good example is saltwater (salt dissolved evenly in water) or air.
- Heterogeneous Mixtures: These mixtures have a non-uniform composition. You can see the different components. Examples include a salad, sand and water, or oil and water.
In summary, matter is classified as either a pure substance (element or compound) with a fixed composition and properties, or as a mixture (homogeneous or heterogeneous) containing two or more substances physically combined.
