SCIENCE

Colloids play an important role in the transport of nutrients and toxins over short and long distances to the ecosystem. Colloids, for example, can carry nutrients such as phosphate to deeper horizons through channels in soil, as well as over much longer distances in surface waters.

In many biological, laboratory, and industrial applications of chemistry, solutions play a very significant role. Solutions containing substances dissolved in water, or aqueous solutions, are of special interest. … Another main component of this unit is quantitative measurements of solutions.

A colloid is one of the three main types of mixtures, with a solution and suspension being the other two. A colloid is a mixture that has particles with a diameter ranging from 1 to 1000 nanometers, but can still remain uniformly distributed in the solution.

Suspensions are heterogenous mixtures where the individual components of the substance can be physically observed (when left to settle). Think about how many oil-based salad dressings separate into two layers in a bottle. Or how a bit of dirt in a glass of water eventually falls in a layer of silt at the bottom. These are all examples of suspensions.

Colloids are also heterogenous mixtures of particles, but the particles in colloids are significantly smaller than those found in suspensions — only 1 to 1,000 nanometers in diameter. Although these particles are very tiny, they remain larger than those found in homogeneous solutions and generate a tell-tell opaque appearance when light is applied to them. Indeed, colloids are often differentiated from solutions via the Tyndall Effect, the scattering of light that occurs when a light beam encounters the particles within a heterogenous mixture. If a beam cannot pass through a substance but rather bounces off it, you know that there are individual particles suspended in that substance reflecting the light, thus making it either a colloid or a suspension. Some examples of colloids include milk, mayonnaise and butter.

A solution is always translucent, and light passes through without dispersing from solvent particles that are molecule-sized. The solution is homogenous and does not calm down. … A colloid is an intermediate between a solution and a suspension. When a suspension splits apart, a colloid won’t break.

Crema is an air foam suspended in an emulsion consisting of water and vegetable oils. You might decide to have orange juice instead of coffee, which, too, is a colloid. It is a sol, a suspension in an aqueous continuous phase of solid particles of pulp.