Mixture

For other uses, see Mixture (disambiguation).

A suspension of flour in water, a heterogeneous mixture

In chemistry, a mixture is a substance made by combining two or more different materials without a chemical reaction occurring. A mixture is very different from a compound. The objects do not bond together in a mixture. A mixture can usually be separated back into its original components. Some examples of mixtures are: fruit salad,ocean water and soil, some examples of heterogeneous mixtures are sandy water, iron fillings, sulfur and salt mixed with sand. Mixtures are the product of a mechanical blending or mixing of chemical substances like elements and compounds, without chemical bonding or other chemical change, so that each ingredient substance retains its own chemical properties and makeup.

While there are no chemical changes in a mixture, physical properties of a mixture, such as its melting point, may differ from those of its components. Mixtures can usually be separated by any mechanical means. Mixtures are either homogeneous or heterogeneous.

Homogeneous mixtures

Solutions

A solution is when a homogeneous mixture of one or more substances (the solutes) dissolved in another substance (the solvent). Solutions have all particles within the size of atoms, small molecules or small ions, less than 1 nanometer (nm) in all dimensions. A common example would be a solid dissolving into a liquid (i.e. salt or sugar dissolving in water or gold into mercury). Liquids dissolve into one another, and sometimes liquids dissolve into gases, for example water vapor and the atmosphere. Common examples include fountain drinks, where carbon dioxide is trapped in the liquid through carbonation. Several solution properties collectively called colligative properties change as a function of solute concentration. Solubility is a compound property.

Heterogeneous mixtures

Main article: Heterogeneous

Heterogeneous mixtures are mixtures with inconsistent, non-uniform composition. The parts of a heterogeneous composition can be mechanically separated from each other. Examples include salad, trail mix and granite.

Suspensions

Main article: Suspension (chemistry)

A heterogeneous mixture in which the particles, of at least one component is larger than 1μm (1000nm) in at least one dimension, larger than colloidal particles. Unlike colloids, suspensions will eventually settle. An example of a suspension would be sand in water another example would be clothing made up of 2 or more materials such as cotton and polyester. Particles of suspensions exhibit the Tyndall effect, that is, they are big enough to disperse light.

Colloidal dispersions

Main article: Colloid

Colloids are heterogeneous mixtures in which the particles of one or more components have at least one dimension in the range of 1 to 1000nm, larger than those in a solution but smaller than those in a suspension. In general, a colloid or colloidal dispersion is a substance with components of one or two phases. It creates the Tyndall effect when light passes through it. A colloid will not settle. Jelly, milk, blood, paint, fog, and glue are examples of colloid dispersions.

Mixtures and compounds

A compound is not a mixture. A compound has very different properties than the elements it is made of, but a mixture contains several substances which keep their properties.

See also

• Concrete#Chemical_admixtures
• Colligative properties
• Molar solution
• Percentage solution
• Plasticizer
• Separation process
• Solubility equilibrium
• Superplasticizer
• Suspension (chemistry)
• Water reducer

External links

• IUPAC Gold Book Definition