A good experiment procedure for detergents and surface tension?

Question

We need it for our 9th grade Science class. Please help me out. Thanks :)

Answer 1

Put water into a shallow pan.
Sprinkle pepper (or somehting similar) all over evenly.
Take a piece of wet soap and touch it to the water.
You will see that the pepper spreads out immediately from the soap showing that it spreads over the surfasce of the water breaking the surface tension.



I've never been able to accomplish the following, but maybe you will have luck.

If you take a small'ish needle, it is possible to GENTLY rest it on the surface of the water (shallow pan again filled with water).

Once you get it resting on the surface you can use the soap again to see if you can sink the needle, showing again the surface tension breaks.




If you fill a glass to the top you can take a dropper and add still more water, and if you look closely at the side while adding water you will see the water 'piled up' showing how the surface tension keeps it from running over. Can use soap again here to.


Too bad you can'r get mercury anymore.....there's a way cool experiment where you can float a steel ball bearing larger than a marble in a small pool of the mercury......heck, I played with mercury as a kid, and I turned out fine...aside from the fact that I went into physics that is. ;)

Answer 2

1) Fill a bowl with water.
2) Sprinkle small particles of something that floats into the water (e.g., talcum powder).
3) Put a bit of dishwashing liquid on your finger, and then dip your finger into the middle of the bowl. Watch what happens to the talcum powder.

This and some other experiments are listed at the website below.