Use household materials for a fantastic and easy science
- A shallow dish – One that is clear is best, to see what’s happening under the surface of the liquid, but a shallow bowl, aluminum pie tin, or plastic or paper bowl will work just fine.
- Milk – The higher the fat content the better. Half-and-half or whole milk works best.
- Food coloring – Four different colors will be more colorful.
- Liquid dish soap ( I think Dawn works best for this experiment)
- A tooth pick or cotton swab
Pour a layer of milk in the dish about (1 cm) deep. Room temperature milk works much better than cold milk.
- Carefully put one small drop of each of the four food colors onto the surface of the milk, widely separated, and not in the center of the dish.
- Get ready to watch what happens! Very carefully drop one drop of dish soap onto the surface of the milk in the center of the dish. You can use a toothpick or cotton swab.
Background Information for the Teacher
The detergent lowers the surface tension of the liquid so that the food coloring is free to flow throughout the milk. The detergent reacts with the protein in the milk, altering the shape of those molecules and setting them in motion. The detergent repels the fat (which is why it helps cut grease on dishes).
Over time during the experiment you will notice the movement of the colors slows down. That is because the soap has now done it’s job and removed the fat from the milk.
Questions for Students:
What did the milk look like when you dropped dye on it?
What happens when you add the dish soap?
Why did the dyed milk disappear? Where did it go?
What do you think will happen?
Can you think of a way this relates to real life? (cleaning up oil spills, washing dishes)
Try this experiment with different types of milk (whole, 2%, 1%, fat free)
Ideas for Interactive Notebook
This lesson on Milk, Detergent and Food coloring is now available in my store! It comes with interactive notebook inserts, informational text article, response pages and more.