Adapted By Kennda Lynch, Elizabeth Adsit and Kathy Zook
July 26, 2012
Moooooogic!
Objective:
Students will use the scientific method to test the difference between using whole milk and
skim milk in this milk and food dye experiment. Students will explore ideas of density, surface
area, convention, and the role of the structure of different types of milk in the experiment.
Colorado Science Standards Addressed:
Standard 1: Physical Sciences
1st Grade: Expectation 1 - Solids and liquids have unique properties that distinguish them
3rd Grade: Expectation 1 - Matter exists in different states such as solids, liquids, and gases
and can change from one state to another by heating and cooling
5th Grade: Expectation 1 - Mixtures of matter can be separated regardless of how they were
created; all weight and mass of the mixture are the same as the sum of weight and mass
of its parts
Adams 50 Science Standards Addressed:
SC.05.31.01.03 Matter exists in different states such as solids, liquids, and gases.
SC.02.51.01.03 Mixtures of matter can be separated regardless of how they were created; all
weight and mass of the mixture are the same as the sum of the weight and mass of the parts.
SC.05.81.03.03 Distinguish between physical and chemical changes, noting that mass is
conserved during any change.
Additional Background Information:
The drops of food coloring stay on the top surface of the milk when dropped onto the milk.
This is due to the fact that the food coloring is less dense than the milk, so it floats on the
surface. The colors do not mix because they were not stirred. When the soap is added, the
soap reduces the surface tension of the milk by dissolving the fat molecules. Students should
notice that this experiment works better for the whole milk versus the skim milk because the
whole milk has a higher percentage of milk fat. 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. 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.
(Modified from: http://www.coolscience.org/CoolScience/KidScientists/tiedyemilk.htm )
Materials:
1. Skim milk and whole milk (Note: milk must be at room temperature)
2. Clear glass or aluminum pie tins (2 per group)
3. Multiple sets of food-dye
4. Dropper bottles of dish soap
5. Plastic beakers or cups (optional: newspaper to covered table)
Adapted By Kennda Lynch, Elizabeth Adsit and Kathy Zook
July 26, 2012
Questions to Ponder
1. Why does the whole milk react differently than the skim milk in this experiment?
2. What is the role of the food dye in this experiment?
Possible Teacher Questions for Students:
1. What happens to the food coloring when you first put it on the milk? Why do you
think that is?
2. What happens when you add the drop of soap?
3. What direction does the food coloring move when you first add the drop of soap?
4. What direction does the food coloring move after the experiment has been running
for a while?
5. Does the movement go on forever? What happens?
6. What happens if you add another drop of soap after the colors have stopped
moving?
7. What did you observe that was different between using whole milk versus skim
milk?
8. Chemically, what is main difference between whole milk and skim milk? Why is that
important for this experiment?
Adapted By Kennda Lynch, Elizabeth Adsit and Kathy Zook
July 26, 2012
Moooooogic Experiment – WHAT’S HAPPENING??!!
Teacher Information
ñWhat happens to the food coloring when you first put it on the milk? Why do you
think that is?
You should see the food dye sitting on top of the milk in small dots. This is because
the density of the food coloring is much less than the density of the milk and so it sits
on top of the milk instead of mixing. The milk also has what we call surface tension,
so the lighter food coloring will sit on top of the milk.
Definition: Density
density is how much something of a set volume weighs. This is generally measured by taking a cubic
centimeter of a substance (cm^-3). If we take a cubic centimeter of some commonly known substances,
we can see that they weigh different amounts:
ñWhat happens when you add the drop of soap?
The soap is what we call a surfactant. A surfactant is a compound that lowers the
surface tension of a fluid and allows unmixable liquids (like oil and water) to mix. So,
for example, this is why you use dish soap to clean up your plate after eating a greasy
cheeseburger. The soap lowers the surface tension of the grease and pulls it away
from your plate.
ñWhat direction does the food coloring move when you first add the drop of soap?
The food coloring should move away from the drop of soap and look like it is
disappearing long the edge of the plate.
ñWhat direction does the food coloring move after the experiment has been running
for a while?
The food coloring will eventually look like it is coming back up from the center of the
initial drop. This movement is because the soap breaks down the fat in the milk,
reduces the surface tension. The milk outside of the soap drop has a higher surface
Adapted By Kennda Lynch, Elizabeth Adsit and Kathy Zook
July 26, 2012
tension and pulls the fluid away from the soap which carries the food dye with it. This
causes what we call convection.
Definition: Convection
The transfer of heat through a fluid (liquid or gas) caused by molecular motion
ñDoes the movement go on forever? What happens?
Nope! Once the soap is evenly mixed with the milk the reaction should stop.
ñWhat happens if you add another drop of soap after the colors have stopped
moving?
The reaction should start again.
ñWhat did you observe that was different between using whole milk versus skim milk?
You should see the food dye convecting (moving) faster in the whole milk vs. the skim
milk.
ñChemically, what is main difference between whole milk and skim milk? Why is that
important for this experiment?
The whole milk has more lipids (another word for fat). Whole milk has about 8 grams
of fat while skim or 1% milk have 1 gram or less of fat.
Definition: Lipids
Lipids are another type of organic molecule (contains carbon). When you think of fats,
you should know that they are lipids. Another type of lipid is cholesterol (see below).
References
http://www.coolscience.org/CoolScience/KidScientists/tiedyemilk.htm
http://www.green-planet-solar-energy.com/definition-of-density.html
http://en.wikipedia.org/wiki/Surfactant
http://www.chem4kids.com/files/bio_lipids.html
Adapted By Kennda Lynch, Elizabeth Adsit and Kathy Zook
July 26, 2012
Name___________________________________
Moooooogic!
Procedure
1. Set up your workstation by getting 2 pie tins and one soap dropper.
2. Fill 2 cups to the marked line inside the cup with milk. One cup should
have whole milk, one cup should have skim milk.
3. Pour the skim milk into one pie tin and the whole milk into another.
4.Carefully put one drop of each of the four food colors onto the surface of
the milk in each, widely separated, and not in the center of the dish. Note:
you will have to share the food dye with other groups.
Your set-up should look something like this:
5.Get ready to watch what happens! Very carefully drop one drop of dish
soap onto the surface of the milk in the center of each dish. (Be careful not
to add the soap directly on top of the food coloring.)
Adapted By Kennda Lynch, Elizabeth Adsit and Kathy Zook
Results
1. What I know…
2. What I want to know…
3. What I learned…
July 26, 2012