Fog is a colloidal solution in which water (liquid, dispersed phase) is dispersed in the air (gas, dispersion medium).

Sols are classified on the basis of size of solid particles present in it. Explanation: When solid particles that are very small in size are present in a continuous liquid medium then the solution formed is known as sol. For example, blood, cell fluid, milk of magnesia etc are all sols.

Milk is a colloid, with tiny globs of butterfat suspended throughout the liquid. Whipped cream is a colloid too. Colloids typically don’t separate into their individual components over time.

Ketchup is a colloid, i.e. a substance that cannot be easliy placed into either the solid, liquid or gas categories. Ketchup is in fact a sol, which is solid particles suspended in liquid.

Colloids contain some particles that are intermediate between those in a solution and those in a suspension. Examples include peanut butter, pudding, Jello, whipped cream, and even fog! Do not separate into layers. Colloids and solutions will not separate into layers; suspensions will.

Examples of Suspension

• Muddy water.
• Milk of magnesia.
• Sand particles suspended in water.
• Flour in water.
• Slaked lime for whitewashing.
• Paints in which dyes are suspended in turpentine oil.

Orange juice is an example of a suspension. In a suspension, the components that make up the mixture may seem to be distributed almost evenly. However, when the mixture is allowed to sit, one component settles to the bottom. When orange juice sits for a while, the pulp settles to the bottom of the container.

If you try to put too much sugar into a cup of tea, it will not fully dissolve and will leave some sugar on the bottom of the cup, making the tea a Suspension. Because tea consists of a solvent (water) and many solutes (sugar cream, milk, etc.).

Milk is not a solution because it has more than one phase suspended in it — it has a liquid phase and a solid phase. Unhomogenized milk is not a solution, it’s a suspension because the fat (aka cream) will separate from the rest of the milk and rise to the top, since fat is less dense than water.

Filtered tea is a colloid and hence it is a heterogeneous mixture. A colloid is a heterogeneous mixture. The solute particles do not settle down when the mixture is left undisturbed.

A colloid has small clumps of one material in another (e.g. milk in water or flour in water). The particles are large enough to block light, so a colloid does not let light pass through, and looks cloudy. If students add enough flour or milk powder, some may settle on the bottom and be classified as a suspension.

Butter and mayonnaise are examples of a class of colloids called emulsions. An emulsion is a colloidal dispersion of a liquid in either a liquid or a solid. A stable emulsion requires an emulsifying agent to be present. Mayonnaise is made in part of oil and vinegar.

Salt water is a true solution and is not a colloid. It is a true solution since salt particles completely dissolve in water.