- 1.1.1 - Science Standard
- 1.1.2 - Science Standard
- 1.1.3 - Science Standard
Prior knowledge & experience:
The purpose of this demonstration is to provide an interesting introduction to a lesson either involving colloids, polar vs. non-polar interactions, suspensions vs. solutions or even possibly simple diffusion. This demo can also be used as opposed to others for its value in including common substances in the chemistry lab. This aspect may help students to connect concepts from the class to everyday life.
Is milk a colloid or s suspension.
Milk contains salts and sugars dissolved in water as well as small globs of fat and proteins that are suspended in the water. These fat globs are hydrophobic, which means they cannot dissolve in the water. The detergent added to the pan has molecules with both hydrophilic and hydrophobic ends. This means that it is able to lower the surface tension of the water, which is approximately 87% of milk. The hydrophobic ends of the detergent molecules try to surround the fat globules in the milk, causing movement of the milk at the molecular level this re-orientation of the different phases of the milk cause the swirling effect we notice when the colours in the milk begin to mix. The movement stops when the re-organization has place most particles in a lowest energy arrangement.
Milk is a solution and not a colloid.
Photographs and Movies
Put all photos in the class Picasa Album and reference here. Do not upload the photos directly to this wiki as there is not enough memory in the website.
Chemistry of Colloids