Milk Art Experiment
Materials
Milk (whole or homogenized)
Cotton Swabs (Q-tips)
Liquid Dish Detergent
Dinner Plate
Food Colouring (many colours)
Method
- Pour milk into the dinner plate until the bottom is covered and allow the milk to settle.
- Add 8 drops of each of the food colouring colours in the centre of the plate of milk. Aim to keep the colours very close together.
- Dip the cotton swap into the liquid dish detergent. Enough to completely cover the tip of the cotton swab but not so much that it will drip.
- Gently dip the soapy end of the cotton swab into the centre of the food colouring drops.
- Observe.
Why it Happens
Properties of substances can change when they interact with one another. For example, adding baking soda to vinegar produces gas; adding flour to water creates a paste.
Milk is an emulsion. An emulsion is a mixture of liquids such as water, proteins, fats and minerals. The chemical bonds between the milk and the proteins are weak and can be easily altered so that the fats and proteins can settle.
The water and milk have similar surface tension. When the detergent breaks the surface tension of the milk a chemical reaction occurs and the dance begins.
The detergent is an emulsifier that sends the fat and proteins off in all directions. This reaction causes the molecules to bump into each other around the dish. When a detergent molecule hits a fat molecule they swirl together. The dance will come to a stop when all of the molecules are evenly distributed throughout.