Colorful Milk and Soap

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Materials

  1. Milk

  2. Plate

  3. Food coloring

  4. Liquid dish soap 

  5. Q tip//Cotton Swab

  6. Potentially useful tool: Talking Color Sensor

 

Procedure:

  1. Pour milk into your plate to completely cover its surface.

  2. At the center of the plate, add one drop of each color of the food coloring into the milk.

  3. Touch a plain cotton swab to the milk in the center of the plate. Check if any reaction occurs.

  4. Dip the dry end of your cotton swab in dish soap.

  5. Place the end of the cotton swab with the soap in the middle of the milk. Check if any reaction occurs.

  6. Try placing the cotton swab in different places on the plate and observe.

Results:

The plain cotton swab should not have any reaction with the contents in the plate. After the cotton swab is dipped in dish soap and placed in the middle of the milk, the food coloring expands away from the center. Putting the side of the cotton swab with the dish soap should also make various designs and reactions when dipped longer or in different areas in the plate.

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Science behind this experiment:

Polarity

The majority of molecules in milk are water molecules, but it also consists of other molecules like fat and protein. These fat and protein molecules are nonpolar, so they do not dissolve in water. The dish soap is made of soap molecules, which have micelles that break up and collect the fat molecules. Then, the polar part of the soap micelle connects to the polar molecule while having the nonpolar milk fat inside it. The soap molecules act as a connection between the polar water molecules and the nonpolar fat molecules in the milk. This causes the nonpolar milk fat molecules to be carried by the polar water molecules. The food coloring allows us to see the connections being formed between the molecules because of the soap. The food coloring molecules move around with the molecules, showing the reaction.

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Further Experimentation

Conducting this experiment with different dish soaps or milk with different fat contents will show the varying reaction based on the molecules of these substances.