Milk Colour Explosion!

in today's science elective we were learning about milk and when you put food colouring and soup into it and this is what happened... 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).

The secret of the bursting colors is in the chemistry of that tiny drop of soap. Like other oils, milk fat is a non-polar molecule and that means it doesn’t dissolve in water. When soap is mixed in, however, the non-polar (hydrophobic) portion of micelles (molecular soap structures in solution) break up and collect the non-polar fat molecules. Then the polar surface of the micelle (hydrophilic) connects to a polar water molecule with the fat held inside the soap micelle. Thanks to the soap connection, literally, the non-polar fat can then be carried by the polar water. This is when the fun begins.

The molecules of fat bend, roll, twist, and contort in all directions as the soap molecules race around to join up with the fat molecules. During all of this fat molecule gymnastics, the food coloring molecules are bumped and shoved everywhere, providing an easy way to observe all the invisible activity. As the soap becomes evenly mixed with the milk, the action slows down and eventually stops. This is why milk with a higher fat content produces a better explosion of color—there’s just more fat to combine with all of those soap molecules.