06 June 2012

Milk, Food Colouring, and Soap Experiment

Drink Factory would like to present an incredible video illustrating the effect of surface tension changes and turbulence as illustrated by 3 simple things: milk, dish soap, and food colouring.  When the dish soap comes into contact with the milk and food colouring it causes the colours to swirl and creates fantastic movement and patterns.
So what exactly is happening here?
Milk is mostly water but it also contains vitamins, minerals, proteins, and tiny droplets of fat suspended in solution. Fats and proteins are sensitive to changes in the surrounding solution (the milk).
When you add soap, the weak chemical bonds that hold the proteins in solution are altered. The molecules of protein and fat bend, roll, twist, and contort in all directions. The food colour molecules are bumped and shoved everywhere along with them, providing an easy way to observe all the invisible activity. At the same time, soap molecules combine to form a micelle, or cluster of soap molecules. These micelles distribute the fat in the milk. This rapidly mixing fat and soap causes swirling and churning where a micelle meets a fat droplet. When there are micelles and fat droplets everywhere the motion stops.

The other thing that is happening is the disruption of surface tension. Since milk is mostly water, it has surface tension like water. The drops of food colouring floating on the surface tend to stay put on top of the surface tension. Liquid soap wrecks the surface tension by breaking the cohesive bonds between water molecules and allowing the colours to zing throughout the milk.

Though a drink made with dish soap isn’t a real possibility it is interesting to think of utilizing a process similar to this with drinks in the future. Imagine being served a drink with another secret ingredient on the side. When you drop it into your drink it becomes a colour explosion!

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