Surface Tension
Question: Why does the food coloring spread out when the soap is added to the milk?
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Hypothesis:
We thought that happens because of a chemical reaction.
Our Experiment
Materials: material
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Procedure:Detail steps so anyone can reproduce this at school or home
Use a numbered list
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Watch us in action:
before starting
after experiment
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The Science behind it
You probably first noticed that the drops of food coloring just sat on the surface where you placed them. That's because food coloring is less dense than milk, so it floats on the surface, and the colors do not mix because you didn't stir the milk.
Then the action began with a drop of soap! The soap reduces the surface tension of the milk by dissolving the fat molecules, which is why fattier milk works better. The surface of the milk outside the soap drop has a higher surface tension, so it pulls the surface away from that spot. The food coloring moves with the surface, streaming away from the soap drop. Due to the convection that results from the moving surface, the food coloring may be drawn down into the liquid, only to appear rising again somewhere else. That's why it's best to use a clear bowl so you can see what's happening.
As the soap becomes evenly mixed with the milk, the action slows down and eventually stops. Addition of another drop of soap will start the process again.
Then the action began with a drop of soap! The soap reduces the surface tension of the milk by dissolving the fat molecules, which is why fattier milk works better. The surface of the milk outside the soap drop has a higher surface tension, so it pulls the surface away from that spot. The food coloring moves with the surface, streaming away from the soap drop. Due to the convection that results from the moving surface, the food coloring may be drawn down into the liquid, only to appear rising again somewhere else. That's why it's best to use a clear bowl so you can see what's happening.
As the soap becomes evenly mixed with the milk, the action slows down and eventually stops. Addition of another drop of soap will start the process again.
Conclusions
Surface tension is what causes this to happen.
About DouglasHello, my name is Douglas and I love playing golf. My teacher is Mrs.Morreale. Also I love science and math.
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About Daniel
Hello, my name is Daniel and I like playing baseball and football. I love math and science. My teacher is Ms.DeBellis.
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