Milk Rainbow Lab (RECORD TITLE IN SCIENTIFIC NOTEBOOK)

Description: Explore the process of the scientific method and lab procedures by reviewing the effects of food coloring and dish soap on milk. Objective: The lesson will demonstrate the properties of surface tension and the effect of soap on the milk. Students will apply soap to milk with food coloring on the surface to visualize the effect of soap on the surface tension of milk. Students will then evaluate specific lab procedures, the importance of the scientific method, and how these topics relate to all scientific concepts.

Research Question: What do you think will happen when a drop of dish soap is added to milk with food coloring?

(RECORD QUESTION IN SCIENTIFIC NOTEBOOK) Background Information: Surface tension is a property of liquids that describes the attraction of liquid particles at the surface. The strong attraction of particles at the surface of the liquid creates a surface “film” that makes moving an object through the surface of a liquid more difficult than moving the object when it is completely submerged in the liquid. Surface tension is also the reason liquids tend to keep a low surface area. Milk is made mostly of water, but it also contains vitamins, minerals, fats, and proteins. Milk has a very high surface tension because of strong attractions between the water molecules. In contrast, soap is a substance that has the ability to reduce surface tension of a liquid. Therefore, when a drop of dish soap is added to milk, the surface tension of the milk is reduced. Hypothesis:(if, then, because statement)

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Materials: Milk Tin Pan Food Coloring Liquid Dish Soap Cotton Swabs Experiment:

1. Fill the waterproof plate with milk and let the milk settle for a minute. 2. Add several drops of different food coloring close together, but separate, in the

center of the milk. 3. Dip a cotton swab in liquid dish soap 4. Touch the cotton swab to the milk’s surface near the drops of food coloring.

Observe the reaction 5. Move the swab to different areas of the plate and observe the reaction.

Observation Notes:

RECORD IN SCIENTIFIC NOTEBOOK CLEAN UP: BEFORE PROCEEDING -- Dump the tin pan in the sink and rinse out pan with water. Pick up any trash around work station and wipe down table with paper towel if messy. Data Collection/Results: Answer these questions.

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1. What happened when the food coloring was first added to the milk? 2. What happened when the soap was added to the milk with the cotton swab?

Conclusion: Answer these questions.

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3. Is your hypothesis valid? Why or why not? What are your next steps if your hypothesis is not valid?

4. Why is knowledge of the scientific method and lab procedures important for all concepts in science?