Praxis: Here’s the dirt on coming clean

By Medicine Hat News on November 10, 2018.

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 É Let’s get started!

*Remember to ask an adult before doing this experiment.

Materials

– 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

Procedure

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@praxismh.ca, http://www.praxismh.ca, 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@praxismh.ca.

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