Aim: To find out why milk "dances" or "moves" when dishsoap is added into it.

Hypothesis: Dishsoap has bipolar characteristics which weakens the chemical bonds that hold the fats and proteins together in the solution.

Apparatus & Materials:

-10mL of milk (whole and skim as used in this experiment)

-Petri dish 

-Toothpick (a Q-Tip would work too)

-Dishsoap (Lemon Ajax dish soap as used in this experiment)

-Cinnamon* (or a coloured powder substance insoluble in milk)

*optional

Observations:

Note that cinnamon was also used in place of food colouring for each type of milk (whole and skim) in order to prove that food colouring does nothing more than make the movement of milk visible to the naked eye.

Discussion: Milk contains droplets of fat (or lipids) which are suspended in the solution. These fats (as well as proteins) are sensitive to changes in the solution around it. Because dishsoap has bipolar characteristics (non-polar on one end and polar on the other) it weakens the chemical bonds that hold the fats and proteins in the solution. The soap's polar or hydrophilic end dissolves in the water content found in milk, whereas the soap's non-polar or hydrophobic end attaches to a fat globule in the milk.

Conclusion: Dishsoap is a surfactant which lowers the surface tension between the fats in milk and the water content in milk. Dishsoap has a hydrophilic end which aligns itself with the water content in milk whereas the hydrophobic end penetrates the surface tension. This causes a reduction in surface tension and an emulsification of the fat and water content in milk.