Types of Mixtures

Homogeneous mixtures are uniform throughout. The composition is the same in all directions in the substance. The types of particles observed in one direction are the same that are observed in all others. A solution of sugar in water is homogeneous.

Heterogeneous mixtures are not uniform. There are pockets of one substance surrounded by pockets of different substances. A mixture of soil in water to make "mud" is heterogeneous. Likewise a mixture of oil and water in salad dressing is heterogeneous.

Types of Homogeneous Mixtures

Solutions

Particle sizes distinguish one homogeneous mixture from another. Solutions are mixtures with particle sizes at the molecule or ion level. The particles have dimensions between 0.1 to 2 nanometers. Typically solutions are transparent. Light can usually pass through the solution. If the solute is able to absorb visible light then the solution will have a color. A blue liquid transmits blue light and absorbs the other colors of the spectrum.

A mixture of water H₂O and ethanol CH₃CH₂OH is homogeneous. The particles are individual molecules of H₂O and CH₃CH₂OH. The two molecules are spread uniformly throughout the solution.

A mixture of water and sodium chloride is homogeneous by chemistry standards. The particles in the mixture are molecules of H₂O and hydrated sodium cations, Na⁺, and chloride anions, Cl^1-.

Solutions are transparent. You can see through them. The mixture remains stable and does not separate after standing for any period of time. The particles are so small they cannot be separated by normal filtration.

A solution may have a "color" but it will still be transparent.

Colloids

Colloids are mixtures with particle sizes that consist of clumps of molecules. The particles have dimensions between 2 to 1000 nanometers.

The colloid looks homogeneous to the naked eye. Fog and milk are examples of colloids.

Colloids frequently appear "murky" or "opaque". The particles are large enough to scatter light. You have experience with the way fog interacts with the light from car headlights. Colloids generally do not separate on standing. They are not separated by filtration.