Just a Needle and a Lot of Surface Tension

Overview

Objectives/Goals The objective of this experiment was to determine if surface tension of water is affected by temperature. Methods/Materials For this experiment 10 containers were used that had different temperatures of water in them. I poured the water into another shallow bowl under a balance made from two tin cans and a wood rod with a needle as the fulcrum. To balance the beam, I used a small amount of modeling clay. A paper basket tied with eight inches of string was attached to one end of the wooden rod. I put pieces of small paperclips in this basket to allow me to measure the surface tension and a triple-beam balance scale to measure the mass of them. On the other side, four inches of nylon string held a needle which rested on the surface of the water. The different temperatures of water were measured with a digital thermometer in degrees Celsius. I heated or cooled ½ cup of water. After measuring the temperature, I put the water into the shallow bowl and rested the needle gently on top of it. Using tweezers, I gently put the small pieces of paper clips into the paper basket until the needle lifted off the surface of the water. Then I measured the mass of the pieces of paperclip. Then using the formula F=2sd (s=surface tension, d=length of the needle resting on the water, and F= (mass of paperclips)x(9.83)x(10^-3) to make it N/g). I repeated did this 10 times for each different temperature. Results 10 trials were taken for five different temperatures of the water. Each trial was measured in grams. I recorded the results in a table and calculated the surface tension with the formula F=2sd where s is the surface tension, d is the length of the needle resting on the water and F is the mass of the paper clips x the gravitational pull of the earth x 10^-3. Surface tension is expressed in Newtons/m. The results demonstrate that as the temperature of the water increases the surface tension decreases and creates a somewhat linear graph. Conclusions/Discussion My hypothesis was proven correct when I discovered that the higher the temperature gets, the lower the surface tension is. There are various examples of surface tension in real life. Temperature plays a big roll in the behavior of a liquid. When the liquid is stretched by something or is poured on a surface, it tends to form the droplets due to the surface tension.

Competition history

• CSEF 2011 Chemistry · Entry J0609

Resources

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