Here’s the dirt on com­ing clean

Medicine Hat News - - YOUTH - Patty Rooks

I do not know about you, but it seems like I can never get caught up on the laun­dry th­ese days! Per­haps one of the is­sues I am fac­ing is that my new laun­dry de­ter­gent is not work­ing as well as I had hoped. Of course, this al­lowed me to stop and think for a mo­ment. Is there a way to “test try” the de­ter­gent to see which kind will work the best in my ma­chine and with the type of wa­ter I have? Of course there is and may I also men­tion that this could be the start of a great Sci­ence Fair Project … Let’s get started!

*Re­mem­ber to ask an adult be­fore do­ing this ex­per­i­ment.


- wa­ter - roll of white cot­ton string - 4 clear jars with tight fit­ting lids - mea­sur­ing spoons - mea­sur­ing cups - three dif­fer­ent kinds of de­ter­gent - some­thing to make the string dirty (soil, juice, grease) - scis­sors - mask­ing tape - marker - spoon - timer


1. La­bel the four jars with the mask­ing tape and marker. For in­stance, you will have “no de­ter­gent” on one jar; “De­ter­gent A” on an­other; “De­ter­gent B” etc. 2. Set aside for now. 3. Choose what you are go­ing to soil the string with. You want it to be the same sub­stance you are test­ing. It is im­por­tant to have this con­trolled in your ex­per­i­ment as dif­fer­ent soaps may clean dif­fer­ent sub­stances bet­ter or worse. We want to test it on the same sub­stance and have a fair test.

4. Cut a 30 cm length of string and soil it with the sub­stance of your choos­ing. Rub it in well for 30 sec­onds. Place one soiled string in each one of the jars.

5. Re­peat un­til you have four strings in each of the four jars.

6. Mea­sure 1/2 cup (125 mL) of tap wa­ter and place it in the jar la­belled “no de­ter­gent.” Re­peat for the re­main­ing three jars.

7. Mea­sure one ta­ble­spoon (15 mL) of “De­ter­gent A.” Pour this into the jar la­beled “De­ter­gent A.” Stir this around gen­tly in the wa­ter for 30 sec­onds.

8. Re­peat with the re­main­ing two strings and de­ter­gents. 9. Set aside for 10 min­utes. 10. Re­move the strings from the wa­ter and rinse gen­tly in clean tap wa­ter for one minute.

11. Ob­serve.

What is go­ing on?

You should have ob­served that de­ter­gent of some kind was bet­ter than no de­ter­gent at all. This is be­cause the emul­si­fy­ing ef­fects of the de­ter­gent in the wa­ter help lift the dirt (or what­ever you soiled the string with) from the string. This should have also been seen by your ob­ser­va­tion skills as the wa­ter with the de­ter­gent in them was likely slightly dis­cloured. I can­not guar­an­tee which de­ter­gent cleaned the best, but I bet your par­ents would love to know this in­for­ma­tion — as would I — let me know how your ex­per­i­ment turned out!

Patty Rooks, Se­nior Sci­en­tific Con­sul­tant PRAXIS, “Con­nect­ing Sci­ence To The Com­mu­nity”. Con­tact Praxis at praxis@prax­, www.prax­, Tweet or fol­low us @Prax­isMedHat, or friend us on Face­book. NOTE our NEW ad­dress: #12 826 11 Street S. E., Medicine Hat, Al­berta, T1A 1T7 Phone: 403.527.5365, email: praxis@prax­

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