Measuring Surface Tension
The surface tension of a liquid can be found by measuring how high a liquid climbs a capillary tube.Copyright Michael Krahe, Wikimedia Commons http://commons.wikimedia.org/wiki/File:Oberfl%C3%A4chenspannung_Kapillareffekt.jpg
Students observe capillary action in glass tubes of varying sizes. Then they use the capillary action to calculate the surface tension in each tube. They find the average surface tensions and calculate the statistical errors.
The chemical engineering of many industrial processes depends on the accurate measurement of surface tension. When an object must be painted or coated with a material, the surface tension of the coating must be carefully maintained to produce the desired coating thickness without any unevenness. The strength and effectiveness of detergents are also partially determined by surface tension. One accurate way to measure surface tension is through capillary action.
After this activity, students should be able to:
- Describe how the combination of adhesive and cohesive forces causes water to rise in a thin tube (capillary action).
- Discuss the role of capillary action in measuring surface tension.
- Practice using scientific notation and calculating experimental error.