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Thread: Emulsifying Experiment

  1. #1 Emulsifying Experiment 
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    I'm kind of new here and not the greatest biologist (i think this applies in this forum) and was wondering if users could possibly help me out with something that has been baffling me.

    The other day my biology teacher for my Grade 12 Academic class showed us a little experiment involving homogenized milk, food colouring, and detergent. I'm aware that the milk is mostly comprised of water and contains some fats, that food colouring is water soluble, and that the detergent is an emulsfying agent (not quite sure what emulsion is), but that is were my knowledge ends. The experiment went like this: We took a petri dish and half filled it with the homogenized milk and let it sit for like two minutes. After it was left to sit, we took four different colours of food colouring and placed them in four different corners for each colour. Once that was done we took a single tooth pick and placed the end in some detergent and then took that end put it in the centre of the petri dish. This caused the food colouring to spontaneously disperse quickly to the edge of the corners and then disappear into the milk. A few minutes later the colours remerged and dispersed once again but slowly in a way that looked like a tie dye commericialswhere different streams of colours moved and swirled. If anyone can explain why these things happen it would be greatly appreciated because i want to impress my teacher and dont avoid sounding condescending because the simpliest anwser is good too. Thanks.

    PS- if you happen to know the properties of those 3 things (milk, food colouring, detergent) please do enlighten me


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  3. #2  
    Forum Freshman Leukocyte's Avatar
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    It's hard to make out what exactly happened in the experiment because I guess it's pretty hard to describe in text. So I'm gonna go have a go at it in the kitchen and see if I can make sense of it


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  4. #3  
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    This looks like a homework question to me, I suggest you start by studying 'surface tension' that will lead you to the answer.
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  5. #4  
    Forum Freshman Leukocyte's Avatar
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    I did it, but I only had one bottle of food colouring and no toothpicks, so it was really bucket chemistry, but it did look pretty cool.

    I'm not sure of the mechanism behind the initial interaction where the food colouring was driven towards the edge of the dish and pulled under the surface (but like billco says it was most likely due to surface tension), but the resurfacing 'tie-dyed' look was due to the emulsifying action of the detergent, as you said - see wikipedia's article on emulsion and then follow the link to surfactants to get a better idea on that.

    I agree with billco here that for homework questions (which seem to pop up in the chemistry section a fair bit) you should try and do a bit of research on your own - wikipedia is usually good, but bear in mind that anyone at all can contribute to articles so sometimes it's good to double-check the facts. Try to look up a chemistry textbook that discusses (like billco said) surface tension, or surfactants (ampipaths) that pretty much any chemistry text will describe in detail.

    Good luck!
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  6. #5  
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    Well, i made up a hyothesis after conducting some research on the emulsion, which i am still unsure about, and this is what i believe occured.
    Since the detergent is a natural emulsifying agent it is suffice to say that as soon as it is in contact with the homogenized milk, it reacts instantaneously to its fat contents. This reaction is emulsion and causes colloid suspension. Surface tension caused by the addition of the detergent forces the food colour to disappear in the uniform white which is the milk. Since the food colouring is insoluble in the water makeup of the homogenized milk does not dissolve in it. This allows the colours to re-emerge completely as they were and stream across the petri dish

    This is a pretty rough hypothesis since it doesnt clearly explain how emulsion works and whether or not it was the reason for the food colouring to be pulled under. I can obviously assume that the detergent influenced it but that isn't factual. I will look into surface tension, but my only source is the internet bc they havent given us our textbooks yet..Anyways, thanks for taking the time to read and give me advice and feel free to add or fix any loose ends in my hypothesis. thanks
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  7. #6 PLZ Help 
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    PLZ HELP I MUST SUBMIT THIS TOMORROW and i'm not sure if my hypothesis fully explains the experiment. If any one can verify it, plz do it would be helping me out a lot. I've transfered to academic and i needed this credit, but i need do well plz help. thanks
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