Analytic/Background Essay



 Lab Report

 Analytic/Background Essay




St. Matt's School Site



  The object of DEEP was to design and test a fully functional lab report. We chose to do Dalton's Law of partial pressures. Though this experiment we have discovered the secret to analyzing results, researching topics, and the miracle of partial pressures.

Our experiment deals with Dalton's law of partial pressures. But, before we can explain our experiment one must know what Dalton's law is. Dalton's law is the law of partial pressures. If a gas is composed by a mixture of gasses, then the total pressured exerted by the gas is partly given out by each of the gasses in the mixture. This means that if there was a mixture of 20% oxygen and 80% nitrogen, 20% of the pressure would be exerted by the oxygen and 80% of the pressure would be exerted by the nitrogen. This relates to Henry's law. Which states that if a gas is under pressure that, over time, the gas will go into a liquid, due to the random movement of the molecules. This is only true if the gases have contact with each other. More on Henry's law. With both these laws it means that different mixtures of gas have different amounts of the gas are forced into the liquid. This is very beneficial to scuba divers, because if they get too much dissolved gas in his blood stream and he rises too quickly, then he can get the bends. This is a very serious and painful condition where you get bubbles of trapped gas the block your joins, which is described more thoroughly in Henry's law. Since partial pressures prevent as much of this gas to enter your body (Blood), it is very important to what sort of air you breath under pressure. Our experiment shows how a scuba diver's blood would react to different mixes of oxygen and nitrogen. See Method and Materials for any questions on our experiment. After pumping up our bottles with different mixtures of oxygen and nitrogen, we let them sit to simulate the time a person would spend at depth. We did this for a much longer period of time than an actual diver would. When we opened the bottles quickly the gas in the water began to bubble, simulating the bends. According to Dalton's law the partial pressures should have determined how much of the gas was forced into the liquid. Since the bottle with the most bubbles was 100% oxygen, then 20% oxygen and 80% nitrogen, and lastly 40% oxygen and 60% nitrogen, it agreed with Dalton's law. This is because 100% oxygen had the largest single partial pressure, with all of the pressure coming from the oxygen. Then with the 40% oxygen and 60% nitrogen the largest partial pressure came form the nitrogen, which was only 60%, so it was the least.

We did our experiment twice, but the first time was a flop, so we only used our second experiment. In our first experiment we did three big mistakes that almost ruined our project, because we were not prepared. Our first mistake was that we use cheap tire valves and a sealant that did not work. With these things, when we filled the bottles they leaked air and when we tried to check their pressure the valves fell into the water. This made us go out and get very good tier valves and sealant. Our next two mistakes were that we put in very pure water and didn't let it sit long enough for the gas to go into the water. This is described in Henry's law. Since we did not let it sit very long there wasn't enough time for the molecules to go into the water. The water was so pure that the gas molecules had nothing to attach to so the came out of the water very easily.

For the most part our data was very reliable, but there was room for improvement. Some of error occurred in the filling of the bottles. We used a pressure gage to tell the amount of pounds per square inch or psi that was in the bottle. Unfortunately we were not very skilled in using the gage and our measurement of the pressure per square inch in the bottles could have been off. Assuming we did not make an error putting the right amount of pressure into the bottle, a problem definitely occurred when we switched from the hose to the cap. When we switched the cap allowed pressure to leak from the bottle. If we were to improve our project we would get someone experienced in the art of using a pressure gage, to fill the tank. We would also improve the way we switched from the pressure hose to the cap. If instead we of covering the bottle with the cap right away we just quickly put some duct take over the lid of the bottle and screwed the cap on over the tape. A major problem in our experiment was the way we covered the lid of the bottle. It was not sealed very well, with a insubstantial sealing job. When the bottle is pressured to its maximum capacity and the two former factors are combined we get a leak. To stop the leak we would have covered the lid with a rubber sealant. With use of rubber seant would we have been able to let the pressure out more quickly. Since we used a cap the pressure was let out slowly because it took some time to unscrew it. If we had used the rubber selant we could have just poked a hole in it, to imideatly released the pressure. Another improvement we could make is to have less water in our bottles. This would improve our project because there would be more pressurized air molecules that could be pushed into the water and there would be less water for the air molecules to occupy. This could produce more air bubbles, which would amplify our results and create a clearer distinction between each the mixtures.

This DEEP program was a great experience for both of us. We have learned more about science and the lessons that go along with it, about diving, how to design an experiment, and about Dalton's law. Thanks to DEEP we have gone though a teachers eye on designing a experiment from scratch. This has provided us a new found respect for our teachers'. The many steps of designing a lab are strenuous and time consuming. Diving is a difficult task to learn, but the DEEP program has provided us an opportunity to learn how to. It consist of complicated dive tables, and intense knowledge. One must learn all about the many pieces of equipment and how they are used. Though DEEP we have learned about Dalton's Law. Not only did I learn about Dalton's Law but I also learned how to research it. To do this we spent many hours on the internet, and books. Deep has given us a very valuable gift for the future.

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