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Surface tension for water and mercury

  1. Oct 14, 2003 #1
    At 20 C degrees the surface tension for water is 73 dyn/cm and mercury is 470 dyn/cm how do I find this value in SI units?

    part 2

    a small capillary tube of 1mm diameter is placed into a container of 20 degree C will the level of the water in the tube move above or below the level of the water? by what distance in meters? Then how do I calculate the volume and mass in kg of the water being moved up or down. Where do I begin? I know there is a formula how do I find it?

    one more really stupid question
    what effect does temperature have on surface tension?
     
  2. jcsd
  3. Oct 14, 2003 #2
    part 1

    The dyn is the CGS unit of force, so:
    1 dyn = 1 g cm s-2

    part 2

    The idea is that the water surface inside the tube is not flat. It curves up towards the wall, touching the wall at an angle smaller than 90°. Experiments have shown that for 'water in glass' you may assume 0°, that means the surface being vertical at the wall.
    So it's the surface tension that holds the water up. Find the total force by taking into account that the tension acts all around the rim. When you know that force, it should be easy to find how much water can be held up.

    part 3

    Surface tension goes down as temperature goes up. Because the inter-molecular distance increases.
     
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