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.

Suspensions are homogeneous mixtures with particles that have diameters greater than 1000 nm, 0.000001 meter. The size of the particles is great enough so they are visible to the naked eye. Blood and aerosol sprays are examples of suspensions. Suspensions are "murky" or "opaque". They do not transmit light. Suspensions separate on standing. The mixture of particles can be separated by filtration.

Artificial polymer colloids

Some examples of artificial polymer colloids (including some that are studied by the KCPC) are:

• paints
• adhesives
• soil conditioners
• carpet backings, paper coatings
• artificial rubber (for tyres, running shoes and so on), Teflon®, neoprene (for fanbelts and wetsuits) - all made by emulsion polymerization, a polymer-colloid process
• flocculants for cleaning waste water (again made by a polymer-colloid process)
• latexes for diagnostic kits

Sometimes, artificial polymer colloids can show opalescence because all the colloidal particles line up and diffract light - even as a liquid!

Natural polymer colloids

Natural polymer colloids are also very common, for example:

• starch (in many foods including rice and potatoes)
• alginate hydrocolloids (for dental impressions, heartburn recipes, etc.)
• natural rubber latex (used for surgical gloves and condoms - vital in preventing the spread of HIV)