penny coated with soap solution

penny without soap solution

Conclusion:

This experiment investigated how many drops of water would fit on one side of a penny in order to test the increase or decrease in surface tension depending on if the penny was covered in soap solution or not. In order to study the problem, eight pennies were tested to see how many droplets of water they could hold on one side. Four of these pennies were covered with a soap solution and the other four were not. Results showed that the pennies covered in the soap solution held less water droplets, therefore decreasing the surface tension, than the pennies not covered in the solution. Based on observations, the water droplets seemed to slip and roll off the soap covered pennies compared to the clean pennies that let the droplets sit on top. This proved that the hypothesis that if the liquid placed on the penny decreases the surface cohesion, then the penny will hold less drops of water was supported because the soap reduced the cohesive force, therefore breaking the surface tension causing the water molecules to have a much harder time clinging together creating the “bubble” on top of the penny. The results from all of the groups were similar with the number of drops on the soap covered penny but the results of the number of droplets on the clean penny varied. Some possibilities for the similarities and differences could be size of the droplets of water let out from the dropper, the amount of soap on the pennies, and the speed at which the droplets were placed on the pennies. To extend this experiment, using different coins such as dimes, nickels, or quarters could be an interesting way to see different results. Questions about the experiment include what other substances cause the decrease of cohesion force? Finally, if the experiment was repeated, some changes to improve the experimental design could be to use other substances along with soap to see the effect of them.