For this week's experiment in class, I told the kids we will scare some pepper. Ofcourse questions like how can you scare pepper as its not live to what can scare pepper came up. I asked them to try making scary faces to see if they could scare the pepper that way. I told them they cant blow or move the setup to scare but can try anything else that doesnt involve touching/blowing etc... Although by this time the kids know me enough that they didnt agree that maybe we are doing some magic.
But first, here's the experiment.
Take a plate and pour some water (maybe half a centimeter deep). Sprinkle some powdered black pepper. Let it rest for a few seconds. You see that the pepper floats (yes, a few grains that are big enough might sink to the bottom but most of it should float.
Take a cotton swab, dip it slightly in dishwashing soap. Now touch/dip the tip of the swab in the middle of the plate without disturbing too much. What closely while doing it to see what happens to the pepper...
What's happening?
At the top of the plate, all the water molecules are close together (since there are nothing else above them to stick to) thus forming what we call "Surface Tension". When we introduce soap in the middle of the plate, the soap breaks the surface tension as the water molecules now can stick to the soap molecules as well...And it starts radiating outwards with the water molecules trying to pull from the rim of the plate but there is nothing to pull back from the center....so the pepper gets pulled to the rim of the plate soon. Now that surface tension is broken, you will also see that the pepper starts sinking down as well.
Can you think of another experiment you can do using the same principle?
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