Experiment I - Observation of Surface Tension - Bio 205 Lab Surface tension buffers Nadiya Abramyuk Prof.Faiza Peetz Experiment I Observation of Surface

Experiment I - Observation of Surface Tension - Bio 205 Lab...

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Bio 205 Lab Surface tension & buffers Nadiya Abramyuk Prof.Faiza Peetz Experiment I - Observation of Surface Tension Object: The following will demonstrate the phenomenon of surface tension. Materials: 2 empty petri dishes, medicine droppers, powdered charcoal, camphor, salad oil, paraffin oil, soap solution, and alcohol 95%. Procedure: A. Fill a petri dish cover 3/4 full of water. Place on white paper. Sprinkle some powdered charcoal on the surface of the water. With the medicine dropper, introduce a few drops of 95% alcohol to the bottom of the petri dish. Observe what happens to the charcoal. Study currents which are visible if you watch carefully. The powder, charcoal, move toward the alcohol and stick together. H2O is being attractive to alcohol. B. Again fill cover of petri dish 3/4 full of water. Place a drop of salad oil on the surface of the water. Add the soap solution. Observe what happens to the drops of oil. Repeat procedures using chloroform in place of soap solution. The single drop of oil merges with water. Some bubbles appear after adding soap and disappears. C. Fill petri dish cover 3/4 full of water. Float camphor particles on the surface of the water. Observe. Add a trace of paraffin oil. What happens? Describe. Explain. Camphor particles in water formed groups and circulating over the whole surface area of the dish. After adding one drop of paraffin oil the motion stop and moved to the border of the petri dish. Experiment II - Measurements of Surface Tension Materials: triple beam or double pan balance, (2) 5m1. Pipette, (4) 50 cc. beakers, 2 petri dishes, 95% alcohol, distilled water, and capillary tubes. Part A - Drop - weight method Object : This method is based upon the weight of liquid drops delivered from the tip of a tube calibrated against known liquids. The weight of the drop is proportional to the surface tension of the liquid. Procedure : From a pipette held vertically carefully add 40 drops of distilled water to a tared beaker on a scale, which is set to zero, and weigh. Repeat once. Rinse pipette twice with 95% ethyl alcohol. Use this pipette to repeat the experiment with 95% alcohol instead of the water. Get average values for the weights of 40 drops of water and alcohol. Weight of 40 drops water alcohol Trial 1: 2.2 g 0.9 g
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Bio 205 Lab Surface tension & buffers Nadiya Abramyuk Prof.Faiza Peetz Trial 2: 1.6 g 0.6 g Average: 1.9 g 0.75 g Questions: a. What ratio of surface tensions between water and alcohol do you calculate using the above data?
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  • Fall '15
  • Dr. Charles Kramer
  • pH, Surface tension

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