 Mixture

A mixture contains two or more chemical substances combined in proportions that need not be fixed. A chemical compound instead has a definite composition: water has two hydrogen chemical atoms per oxygen chemical atom, whereas a sucrose and water mixture can contain different sugar proportions. A homogeneous mixture has uniform composition on the scale of representative samples; a heterogeneous mixture has distinguishable regions of different composition. A chemical solution is homogeneous, whereas sand dispersed in water is a particle suspension.^[ref]

The distinction concerns the sample, not merely its ingredient list. A vessel with dissolved sodium chloride and excess undissolved sodium chloride contains a chemical solution and an ionic crystal thermodynamic phase. The liquid portion can be homogeneous while the whole vessel is heterogeneous. Similarly, molecular oxygen dissolved in water is part of a chemical solution; visible gas bubbles introduce a separate gas thermodynamic phase.

A mixture is a combination of two or more substances that are not chemically bonded to each other. The components of a mixture retain their individual properties and can usually be separated by physical means. Mixtures can be classified into two main categories: 1. **Homogeneous Mixtures**: These have a uniform composition throughout. The individual components are not easily distinguishable. Examples include solutions like saltwater or air. 2. **Heterogeneous Mixtures**: These consist of visibly different substances or phases.