If you think you have never stumbled across a thing called “colloid”, you are most certainly wrong. Have ever seen the wiggly Jell-O? That is a colloid. What about deodorants and perfumes? Yes, they are colloids as well. In fact there are so many colloids that we use or come across in our daily lives that we should be mindful of them. Milk is also a colloid and so is the cheese that they put in your pizza. Can you find a link between these examples of colloids and come up with a befitting definition?
What is a colloid?
A colloid is a system of two distinctly different kind of particles. Such a system is called a heterogeneous system as it has separate boundaries of separation between the two kinds of particles. If you mix yellow and red gummy bears, you will get a heterogeneous system of gummy bears. You can pick and separate the two different of kind of gummy bears through a physical process. Air, on the other hand, is what you would call a homogenous mixture. It contains a mixture of gases which you cannot separate and there are no boundaries of separation between the different kinds of molecules of nitrogen, oxygen and the rest of the gases. Some scientists believe that the particles that dissolve in a solution and the particulate matter that compose the colloids are not so different and regard colloids as homogeneous mixtures. Although, there are no strict definitions, one must resort to tradition when approaching such matters.
Dispersed phase and medium
All colloid systems are composed of a dispersed phase and the dispersed medium. The dispersed phase and medium can be of any of the three states of matter: solid, liquid and gas. The medium must be continuous and the dispersed phase must be dispersed in it, meaning it should not settle down at the bottom of the container and keep on floating for a long time. Did you know that dust is a colloid that has a solid dispersed phase and gaseous dispersed medium? If you need an example of a gaseous dispersed phase in a solid dispersed medium then look no further than your eraser.
Tyndall has an effect
The Tyndall effect is a phenomenon that we observe in our everyday life. When you open the window in the morning, there are small particles of dirt or dust coming in which sparkle or shine. These dust particles can be thought of as the dispersed phase and air as the dispersed medium. This effect occurs for colloidal solutions which have a dispersed phase which very keenly scatters any light that hits it and a dispersed medium which otherwise provides no hindrance to light and allows it to pass through. The glitter filled lava lamps are colloidal systems that provide a great example of Tyndall effect. The glitter is the particulate matter that scatters light that falls on it and bounces it off in different directions. The glitter remains in a suspended motion, as if they have almost stopped moving but not quite, inside the lamps.