THE CAT'S MEOW / MILK CO-MOTION
To observe the interaction of detergent with the fat of the milk and food color
1. Provide a possible explanation of phenomenon you observed based on the
result of your experiment.
When food color is added to milk, it floats because it is less dense than milk. The non-polar fat in the milk prevents the food color from spreading, as it cannot participate in hydrogen bonding with water. When detergent is added to milk and the food color, the non-polar ends of the soap molecules attracts towards the non-polar fat of milk, and the interaction of the detergent with the fat in milk results the food color to swirl around. Whenever the detergent touches the milk, it breaks up the drops of fat, which spread out, allowing the food coloring and milk to mix. The food coloring swirls into the places where the fat was.
Detergent molecules dissolve fat of milk by having one hydrophobic end (which interacts well with the fat) and one hydrophilic end (which interacts well aqueous part of the milk).
2.How would the results of this experiment differ if:
a)Skim milk was used?
(Milk from which the cream (fat) has been taken is called skimmed milk.)
If skim milk was used, the drops of food color would dispersed in milk without
the need of detergent because all the fats has been taken out of milk and it allows
the food color to dissolve in it.
b)Homogenized milk was used?
(Homogenized milk is the milk in which all the fat are mixed so that it does not rise on the top)
Fat is insoluble in water. Water-soluble food colors will spread and dissolve in water, but their motion would be slow if homogenized milk was used,