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LESSON 7: Milk Rainbow - chemed.org

92 LESSON 1:Goofy Putty92 LESSON 1:Goofy PuttyYou Be The Chemist Activity Guides |page 92 You Be The Chemist Activity Guides |page 92 You Be The Chemist Activity Guides |page 92 You Be The Chemist Activity Guide |page 92 LESSON 7: milk RainbowESTIMATED TIMES etup:5 minutes|Procedure:5 10 minutes DESCRIPTIONC reate swirls of color in milk and explore a propertyof liquids known as surface tension. OBJECTIVEThis LESSON will demonstrate the property of surfacetension and the effect that soap, a surfactant, has on thesurface tension of milk .

You Be The Chemist®Activity Guide |page 94 LESSON 7:Milk Rainbow LOWER GRADE LEVELS/BEGINNERS Use Lesson 15: Floating Paper Clipsto introduce the concept of surface tension. Then, perform this experiment to add some color to the lesson and explore

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Transcription of LESSON 7: Milk Rainbow - chemed.org

1 92 LESSON 1:Goofy Putty92 LESSON 1:Goofy PuttyYou Be The Chemist Activity Guides |page 92 You Be The Chemist Activity Guides |page 92 You Be The Chemist Activity Guides |page 92 You Be The Chemist Activity Guide |page 92 LESSON 7: milk RainbowESTIMATED TIMES etup:5 minutes|Procedure:5 10 minutes DESCRIPTIONC reate swirls of color in milk and explore a propertyof liquids known as surface tension. OBJECTIVEThis LESSON will demonstrate the property of surfacetension and the effect that soap, a surfactant, has on thesurface tension of milk .

2 Students will apply soap tomilk with food coloring on the surface to visualize theeffect of soap on the surface tension of milk . Thelesson can be extended to discuss a type of mixturescalled emulsions. CONTENT TOPICSS cientific inquiry; states of matter; properties ofmatter; attractive forces (surface tension); mixtures MATERIALSoWhole milk oWaterproof plate or shallow bowl oFood coloring oLiquid dish soap oCotton swabsAlways remember to use the appropriate safetyequipment when conducting your to the Safe ty Firstsection in the Res our ce Gui deon pages 421 423 for more detailed information aboutsafety in the ahead to page 95 to view theExperimental & RESEARCHBACKGROUNDM atter exists primarily as a solid, liquid, or gas on theearth.

3 Solidshave a definite volume and a definite shape. Examples of solids are chairs, books, and a definite volume but no definite of liquids are water and orange juice. Gaseshave no definite shape and no definite of gases are the oxygen we breathe and thehelium that fills balloons. Along with differences in shape and volume, the differentstates of matter have other unique properties. For example,surface tensionis a property of liquids that describes theattraction of liquid particles at the surface. The strongattraction of particles at the surface of the liquid creates asurface film that makes moving an object through thesurface of a liquid more difficult than moving the objectwhen it is completely submerged in the liquid.

4 Surfacetension is also the reason liquids tend to keep a low surfacearea. For example, water droplets will tend to form into asphere rather than spreading out is a white liquid produced by female mammals andis the primary source of nutrition for young mammalsNATIONAL SCIENCE EDUCATION STANDARDS SUBJECT MATTERThis LESSON applies both Dimension 1: Scientific and Engineering Practicesand Dimension 2: Crosscutting Conceptsfrom A Framework for K 12 Science Education, established as a guide for the updated National Science EducationStandards.

5 In addition, this LESSON covers the following Disciplinary Core Ideas from that framework: : Structure and Properties of Matter : Chemical Reactions : Forces and Motion : Influence of Engineering, Technology, and Science on Society and the Natural World (see Analysis & Conclusion)You Be The Chemist Activity Guide |page 93 LESSON 7: milk Rainbowuntil they can digest other foods. Humans, especiallychildren, often consume the milk of other mammals as apart of their diet. In the United States, cow s milk isproduced on an industrial scale and is the mostcommonly consumed form of milk .

6 milk is made mostlyof water, but it also contains vitamins, minerals, fats, andproteins. Water has a very high surface tension because of strongattractions between the water molecules (hydrogenbonding). Because milk is primarily water, it also has a high surface tension. In this experiment, the highsurface tension of the milk supports the dye moleculeson the surface and keeps the dye relatively centralized.(The tendency to keep a low surface area minimizes the distance that the dye will spread across the milk ssurface.) In contrast, soap is a surfactant.

7 A surfactant(or surfaceactive agent) is a substance that has the ability to reducethe surface tension of a liquid. Therefore, when a drop of liquid dish soap is added to milk , the surface tensionof the milk is reduced. As this occurs, the fat (butterfat)and protein particles in the milk can move more freelyand easily. In addition, the soap interacts with the fat andprotein particles in the milk , causing the particles tomove around. This action can be seen as the dye swirlsthrough the & EQUATIONSMilk is a liquid made mostly of water, but it also containsvitamins, minerals, fats, and proteins.

8 milk is a uniquesubstance known as a colloid, so it does not have aspecific chemical formula. A colloidis a mixture in whichvery small particles are spread evenly through anothersubstance. In milk , the fat globules, proteins, vitamins,and minerals are spread throughout the water. The molecules that make up soaps and detergents havetwo main parts (ends) that behave differently. One end ofa soap molecule is attracted to water, while the othercomponents are repelled by water but attracted to drops of liquid dish soap are added to milk with drops of food coloring on thesurface, the soap will reduce the surface tension ofthe milk and react with the fat.

9 This interaction willcause the particles in the milk to move around andcreate swirls of TO THE YOU BE THECHEMISTCHALLENGEFor additional background information, pleasereview CEF s Challenge study materials online Additional information on states of matter andproperties of matter, including surface tension,can be found in the Classification of Mattersection of CEF s Passport to Science Exploration:The Core of FactThe fat content of milk dependson the type of milk (skim, whole,etc.) and the type of cow. Holstein-Friesian cows tend toproduce milk with a lowerpercentage of butterfat thanJersey Be The Chemist Activity Guide |page 94 LESSON 7: milk RainbowLOWER GRADE LEVELS/BEGINNERSUse LESSON 15: Floating Paper Clipsto introduce the concept of surface tension.

10 Then, perform thisexperiment to add some color to the LESSON and explore the concept further! Pour small drops of water on a plate to illustrate surfacetension. Students should notice that the water does notspread out completely. Instead, it will form droplets, andthose droplets will attract other small droplets to formlarger puddles. HIGHER GRADE LEVELS/ADVANCED STUDENTSDESCRIPTIONE xamine the composition of the milk and how soapinteracts with the components of the LESSON examines the properties and composition ofmilk and uses soap to illustrate the effects of surfactantson the properties and components of & RESEARCHMost of the things around us are mixtures, like the air webreathe and the orange juice we drink!


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