Science Buddies: "Ask an Expert"

Hi,


I am in 8th grade and my Science Fair is fast approaching. I like the look of this project: https://www.sciencebuddies.org/science- ... shtml#help

Which is measuring the surface tension of water, but the procedure is confusing me quite a bit. Could someone help me understand the procedure and/or put it into simpler terms?

Thanks!

MZMZ - The simplified explanation of this experiment goes something like this. You are constructing a sensitive balance using a straw or some other light material. From one end you hang a small receptacle to contain your counter balance weights - small pins, drops of water etc. From the other end you hang a small needle or straight piece of wire - a paper clip was suggested. You carefully add a small weight to the beam - like modeling clay - to perfectly adjust the beam so it is perfectly level, the needle and wire in perfect balance with the container. You carefully raise a small dish of water (or other liquid you are testing) so that the needle or wire, which is also perfectly level, just touches the surface of the water. Surface tension will tend to hold it on the surface, keeping it from sinking. The test begins when you slowly and carefully start to add units of weight to the pan (pins or water drops) until the surface tension of the liquid acting on the needle or wire is just overcome and the needle breaks free and rises out of the water a very small distance.

When you've done that, calculate the weight you added to the receptacle and process it through the equation for calculating surface tension "s" which is the surface tension per unit length, in units of newtons/meter (N/m).

Hope this helps a bit.

Rick Marz