Chemistry

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tplilipad
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Chemistry

Post by tplilipad »

I worked with my granddaughter on a Science Fair Project. She wanted to find out which of three laundry detergents would best remove ketchup stain from 100 percent cotton fabric. We bought 3 detergents from a list of top 10 we found on line. One did not mention its ingredients. Another listed some ingredients and gave a website or 800 number to call. One listed all of its ingredients. She learned about surfacants and enzymes.

She tested each detergent for its ability to remove ketchup stains by putting the same amount of ketchup on cotton squares.Then like a normal 4th grader would do, she wiped off excess ketchup with a paper towel. The amount of water changed in each of three tests (500mL, 355mL, and 237mL). She used plastic containers with lids as "washing machines".
The amount of detergent remained the same each time: 1mL.

She chose the detergent that removed the stain best (but not completely)...now we have a question. Why did the the "washing machine" with the most water (500mL) remove each of the stains better than the other two lesser amounts of water?

We are thinking because ketchup contains vinegar which we found out contains 80% water, that it is a water-based stain and, therefore, required MORE water, rather than less to clean. We thought the same amount of detergent with less water would remove the stain better. Can you help us? Thank you so much. Pam Lillis (Gram) and Charlotte Patty (4th grader)

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tdaly
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Re: Chemistry

Post by tdaly »

Hi tplilipad,

Thank you for being so detailed in your post! It makes it much easier for us to help you.

Too much laundry soap can actually make the detergent less effective because the detergents are designed to work at a particular concentration. So, both too much detergent and too little detergent can be problematic. In addition, you need some movement between the fibers in the cotton to help get the stains out. (This is why rubbing a fresh stain under cold water does a better job of removing the stain than simply putting the stained item in a sink of cold water.) I suspect that the combination of these two factors contributed to the results that you got.

Post back if you have other questions or want some additional clarification!
All the best,
Terik
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