Penny Lab

This experiment investigated if the pennies being dipped into a soap solution would change the amount of water drops the pennies could hold before spilling over the edge.

In order to study the problem, as many water drops as possible were placed on a penny before it spilt over the edge with nothing else on the penny. This was repeated 4 times. The average amount of water drops the pennies could hold was then calculated. Next, the pennies were dipped in the soap solution and the same process was followed (water drops until it spilt over the edge and repeated 4 times) and the average was then calculated. The results from both part one and part two were compared and…

Results showed that the soap solution did, in fact, reduce the cohesive force of the water. The results from part one were much more successful with an average of 18.5 water drops that a penny was able to hold, compared to part two with an average of 5.5 water drops.

This proved the hypothesis that if the pennies were dipped in the soap solution then it would reduce the cohesive force of the water. The hypothesis was supported because the soap reduced the “strength of the surface skin of the water.”

*I wasn’t there for the experiment in class so I do not have the results of the class to compare to my own…*

To extend this experiment, instead of only using only pennies other coins could be used with a bigger surface area. It would be interesting to see if it would have the same effect, just on a bigger scale. Another way to extend the experiment would be to use a different soap solution to see if it had the same effect as the one used. Would it have the same effect and reduce the cohesive force of the water? Or less soap solution could be left on the penny, or soap solution could be put on only one half of the coin so that way when the water is dropped on, it would be evident which side it’d be gravitating towards.

Finally, if the experiment was repeated, some changes to improve the experimental design could be that the pennies are left in the soap solution for the same amount of time, or that the exact same amount of solution would be on the penny. For example, the way that the water is dispensed on the penny, by an eye dropper, the solution could be done the same way. That way how much solution is used is controlled so that it’s not overflowing, but also it ensures that there is the exact same amount as the other pennies. Another thing to improve this experiment would be to repeat it more than 4 times.

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