In our project we were trying to show Henry's Law. Henry's Law states
that the amount of gas molecules that can be dissolved into a liquid is proportional to the pressure of the gas. When the gas is under high pressure more of the gas will dissolve into the liquid. But when the pressure of the gas is decreased, the gas molecules will not remain in a dissolved state, they will bubble out of the liquid. This law directly relates to the effects of pressure on the divers as they descend deeper into the water. This is so because blood is a liquid and the pressure being put on the diver goes into the blood. The further the diver goes down, the more pressure there is being put on the lungs.
In the bottle there is enough pressure to dissolve
the gas into the liquid. At this point there are about fifty pounds
per square inch of pressure already in the bottle. When you open
the bottle at the surface the pressure drops to 14.7 pounds per
square inch. This is equal to one atmosphere. So at the surface
there will be a lot of bubbles because there is not a significant
amount of pressure. When you take the bottle down to five feet
below the surface there are also fifty pounds per square inch
of pressure in the bottle, but when you open the bottle at this
depth the pressure drops to about 16.8 pounds per square inch.
Then when you take the bottle down to ten feet and open it the
pressure again will drop. This time the pressure will drop from
fifty pounds per square inch to about 19 pounds per square inch.
Finally, when you take the bottle down to seventeen feet the pressure
will drop from fifty pounds per square inch to about 22 pounds
per square inch. As you can see as you go further into the water
there is more pressure put on the bottles at the different depths.
This results in a noticeable decrease in the amount and size of
the bubbles in the bottle. There is high pressure inside the bottle
as well as outside the bottle. When the cap is opened at the bottom
of the pool (seventeen feet), where there is a high pressure,
there will be fewer bubbles. Keeping this in mind, think about
how far you would descend in order to have no bubbles when you
open the bottle. You would have to go very deep into the ocean
to be able to open a bottle and see no bubbles come out. If a
diver surfaces too fast from a great depth, they will get a condition
called "The Bends." The Bends occurs when a diver is
down deep in the ocean too long and having a large amount of pressure
on your body. After being at a great depth for too long and then
rising too quickly can cause your blood to start to bubble. It
bubbles because of the nitrogen that is forced from the lungs
into the bloodstream. After ascending to the surface the diver
must be taken to a decompression chamber to have the nitrogen
dissolved back into a liquid. It takes a long time because if
they decrease the pressure to make the gasses in the blood dissolve
back into a liquid. If the diver rises too quickly, it is exactly
like opening a club soda bottle.
The results of our experiment matched our hypothesis perfectly. Our hypothesis said that as we went deeper into the pool, the amount and size of the bubbles would decrease. Our results show that there is a decrease in the time of the "Big Boom." The "Big Boom" is the great explosion of bubbles when we first opened the bottle at various depths. The results also show that there was about a .21 second drop at each depth. We did three trials at a depth of five and seventeen feet and two trials at ten feet. There was an 8.1% decrease from five feet to ten feet. From ten feet to seventeen feet there was an 8.4% decrease. As we mentioned before, there was also a very noticeable change in the size and amount of bubbles at the different depths. At five feet, there were many large amounts of bubbles and the bubbles were pretty big. At 10 feet, the change in bubbles was noticeable but there was still not much change. The bubbles were smaller and there were fewer of them. But at seventeen feet, you could tell a definite change in bubbles from five feet. The bubbles were significantly smaller and there were fewer in number when we first opened the bottle and there was the "Big Boom."
Our results relate to a real diver because the results show that as you go deeper, more pressure is put on the body. Because there are fewer bubbles releasing out of the bottle at greater depths it shows that the gas is being dissolved into a liquid. In the human body, this is the nitrogen being forced and dissolved into the bloodstream.
For each depth, we found the percent of error
in all of the trials. For five feet, the percent of error in our
trials was only three percent. At ten feet, the percent was larger.
It came out to be 10.6 percent error. At ten feet, we only had
two trials, instead of three. We think that this could be one
reason why there was so much more of an error at this depth. Finally,
at seventeen feet there was a 2.4 percent error. The percents
of error at five and seventeen feet, was only .6 percent off.
These two percents were a very close in error. The percents were
very small considering the experiment that we attempted to complete.
There could have been many different things that could have happened during this experiment that would have caused a lot of error in our results. Since we used stopwatches, we did not start them on the exact time. As you can see this happened when we were at 10 feet. One trial we timed it to be 2.76 seconds and the other time we got 2.23 seconds. As you can see, this is a pretty significant difference because, there was a .53 seconds between these two times. The average for this depth was 2.5 seconds. One time that we were doing the experiment at ten feet; the stopwatch did not work. Because of this, Lucy had to count the minute in her head. That did not work too well. This affected our results because Lucy did not count at the same time, as the watch would have timed it, because it was an approximation rather than a measured amount of time.
There were some things that we could have done better if we were to repeat the experiment. One thing we could do is test the bottles at greater depths. For example, we could try it at 60 feet, a totally different atmosphere. Since there is a much greater amount of pressure at each atmosphere, this would make our experiment more interesting. We also could have found a better way to express our results. We used a video that shows our experiment very well, but we could have used graphs and tables to show our results better. But all in all, this experiment was a very fun and educational experience.
We learned so much from this experiment. We learned a lot about Henry's Law and scuba diving. We learned how to scuba dive and it was fun to be able to do something that not many kids in middle schools have the chance to experience. We will also get to learn even more from our classmate's projects. This wonderful program provides us with the chance to go into further detail about physics and all the different laws that go along with it. We had the greatest time doing this with our classmates!