Many people have never heard the terms hydrophobic and hydrophilic. Hydrophobic means that the substance does not combine or mix well with water. Athletic apparel, such as Nike Dry-Fit, uses hydrophobic coating on the material. This wicks the moisture from the fabric, keeping you dry in all weather. Some examples of day to day hydrophobic substances are oil and Crisco.

    Hydrophilic means that the substance mixes with water because it has strong polar groups that readily interact with water. Soap and sugar are examples of hydrophilic substances.

We found from our results that when using hydrophobic coating, the ball falls through the tube faster. We found that the average time it took the ball to go through the tube was 11.8 seconds(≈6 in/sec.) when it was coated with hydrophobic coating. While when using hydrophilic coating, it took an average of about 13.5 seconds (5 in/sec). When we used no coating it took an average of about 13.8 seconds (≈4.8 in/sec.). The hydrophobic coating caused the ball to move a little more than 7% faster than the ball without any coating. Through this, we proved that some objects underwater can move quicker when coated with hydrophobic coating.

Our data indicates that hydrophobic coating is significantly affecting the ball, making it travel faster through the water than the hydrophilic coating. Using this information, one could choose to coat boats, submarines and other underwater vehicles so that their speed would increase. Also, this information can explain why certain underwater animals, like penguins, have a hydrophobic skin. They most likely evolved to have this trait because having hydrophobic skin proved to be an advantage over other types of skin. Also, some insects that do not swim in the water but move on the surface of the water have hydrophobic legs. This keeps their legs dry and might allow for less drag from their legs on the water, making them go faster. Overall, we learned that the coating on something can greatly affect its speed through the water.

To show how beneficial to the environment using hydrophobic coating would be to the fuel efficiency of a cruise ship here are some statistics:

The average cruise ship uses 200 gallons of gas per nautical mile traveled. If boat manufacturers were to coat boats with hydrophobic coating one could save 14 gallons of gas per mile traveled. The average cruise ship travels 625 nautical miles per day. This means the average cruise ship uses 125,000 gallons of gas per day. If this ship was coated with hydrophobic coating it would save about 8,750 gallons of gas. While this does not seem like a great amount of fuel saved, if all cruise ships were coated with hydrophobic coating, it would greatly increase the fuel efficiency of the boats, according to our data.

Another example of how beneficial the use of hydrophobic coating is to not only the Earth, but people, is in municipal water mains. Every year, cities spend a great amount of vital energy pumping water through the local pipes. If the Department of Water and Power were to coat the inside of pipes with a hydrophobic coating, the water would slide easier through the pipes, using much less energy per year and saving taxpayers money.

Because we wanted to eliminate as much human error as possible, we decided to use the Vernier Labquest Photogate sensors to record the amount of time it took the ball to fall through the tube. Although we eliminated the form of human timing error, we still had many other sources of error. The first is the variability of the drop height. We tried to drop the balls from the same height each trial, but because we did not have a line or point where we were consistently dropping the ball from, it changed slightly, which caused a few outliers. Another source of error we could have had was the ball hitting the sides of the tube while dropping to the bottom. This would cause the ball to slow down, causing more error.

When looking at our results, we eliminated the results that were clearly outliers. We are not sure what went wrong in our experiment to cause the outliers, but we know something went wrong because the results were completely out of the range of the other data. To make up for the data we lost, we did new trials that turned out close to our average. These extra trials allowed us to get even more accurate data.

Throughout the experiment process, we discovered that many of the key pieces to our experiment needed to be altered or completely taken out. First, we found that when the ball was coated in hydrophobic coating, and placed in a pantyhose bag that was coated in hydrophobic coating, it floated. We also tried to drop a ball with no coating in a pantyhose bag; it also floated. We then came to the conclusion that the ball would not sink with the addition of the pantyhose bag unless weights were added. If we would have known this before we started the experiment, we would have used more weights or a heavier ball for all of the trials. Secondly, it would have been beneficial to have used our time more efficiently toward the beginning of the process. We spent a great amount of time simply figuring out how to get our large pipe to stand up. We first tried to position our pipe in a bucket full of concrete. This idea did not turn out well because the pipe did not stick and stay in the concrete well, and we would have been stuck with carting around a 100 pound bucket. After we had decided against the concrete bucket method, we realized we could simply duct tape the pipe to a wall. If we had figured out that we could stand the pipe up by attaching it to a wall from the beginning, we would have had more time for the completion of our experiment. In conclusion, if we did our experiment again, we would have chosen a heavier ball and we would have found a good way to attach our pipe earlier in the process.

Some things that could be added are different shaped objects. With this addition, we could have tested for a difference with the different shapes and coatings. This would combine the element of hydrodynamics to our experiment. Another possible addition would be the incorporation of a mini submarine that we could coat with the different coatings. This would allow for more realistic results for the use in submarine travel. Another possible adaptation to the experiment would be to test hydrophobic and hydrophilic coatings in different liquids.