Scuba Dive!

Introduction:

Scuba diving is a recreational sport that is enjoyed by thousands of people world-wide.  However, it is also one of those sports that can be fatal if the equipment malfunctions or if the divers are careless.  The SCUBA tank (Self Contained Underwater Breathing Apparatus) was invented by the famous underwater scientist, Jacques Cousteau and it revolutionized underwater exploration.  It changed diving from a hazardous and difficult operation involving long hoses and heavy suits to a relatively simple operation where the diver carries his own air supply. 

The Participants:

You may in pairs or in triples (no more than 3).  However, since there are "more heads," it is the expectation that the overall quality and quantity of work will increase relative to the number of people involved.  You must clearly identify "who did what" in written form within the project.  Also, you need to determine when you will work with the others on your team and if the times will work with the other's personal schedules.

The Task: The gas laws are used to determine the pressure of compressed air in a scuba tank.  This project will require you to make some basic measurements necessary to calculate the amount of air required to remain underwater for a given time.  You will devise a method for measuring the amount of air you would breathe in 30 minutes.  Then, using the appropriate gas law, you will calculate the final pressure of a scuba tank holding that much air (Assume that the temperature remains constant and the interior cylinder dimensions of your scuba tank are 8 inches in diameter with a height of 26 inches).  You will then create a PowerPoint presentation OR a web-page describing your work.

The Procedure:

Design a method to determine the volume of air needed for 30 minutes of breathing.  This will likely be your biggest challenge.  (Note: A bag's stated size is what it can hold when it is completely open.  When the top is pulled together to blow into, the volume is reduced considerably.)  The volume of air actually used in scuba diving varies substantially among divers on the same dive, so that there is no single "right" answer.  Because scuba diving involves exercise (swimming), you will need to figure out a way to exercise while measuring the air you breathe.  What is important here is that you devise a workable plan and carry out your experiment scientifically.  In addition, since while we use English units for measurement here in the United States, scientists around the world use the metric system.  So, where ever you encounter English units, you must first convert them to metric units before any calculations are made.

Data: Organize your data into a table with appropriate headings and units.  If your collection of data lends itself to a representative graph, be sure to include your graph.  All English measurements (gallons, inches, cubic feet, etc.) must be converted into metric measurements BEFORE you make your calculations!  All answers must be reported in the metric system.  Remember, what are the METRIC units for volume?  For pressure?

Questions to Answer:

1.     How did you determine what volume of air would be required?  Describe the materials, the process and the procedure that you designed yourself and used.  Be detailed.  Remember, you may NOT use anything like spirometers or air flow meters.  You must design the device yourself.
2.     What volume of air did you determine would be required for a 30 minute dive?  Be sure to include ALL your calculations.  Again, remember to convert all non-metric units to METRIC before making any calculations.
3.     Use the appropriate gas law to make the calculation of final pressure that your air will be under when it is in the tank.  Which gas law will you use?   Assume that the temperature remains constant and the interior cylinder dimensions of your scuba tank are 8 inches in diameter with a height of 26 inches - convert into metric volume units first before making any calculations for volume.
4.     The volume of air that you calculated for a 30 minute dive was the volume of air breathed on land.  What volume of air would you need to compress for a 30 minute dive at a depth of 10 meters?
5.     Why might it be important to consider the temperature of the water where the dive would occur when doing the calculations for this experiment?  Would the amount be different for diving up off the coast of Maine in June compared to diving off the Florida Keys in that same month?  What would happen?
6.     If 3750 L of air must be compressed into a 26L tank, what will be the final pressure of the air in the tank?  Assume that the air is originally at atmospheric pressure.
7.     Why are pressurized tanks required for deep scuba dives?  What can happen?
8.     What might happen if an overfilled scuba tank was left sitting in the sun on a hot day? Why?
9.     Use what you have learned about scuba diving to hypothesize what problems might be encountered in a suddenly depressurized airplane cabin at 30,000 feet.  What would happen?  Why would it happen?

The Report:

You will EMAIL US one of two options:  (Note - for Spring 2008 - students have the Word Document choice as well....)

• PowerPoint presentation (Office 2000 or later):

  • Must contain a minimum of 15 slides.

  • Must include clip art, original art, color and/or graphics.

  • NOTE: In order for a movie to play within a Microsoft Power Point, the supported movie file formats are: .asf, .wma, .wmv, .wm

  • Movies that require QuickTime (Apple products) will NOT be fine and will NOT run within a Microsoft product (thank Bill Gates for that one....).

• Web page.

  • If you use your own server space, all you need to do is email us the fully qualified URL.

  • Must include clip art, original art, color and/or graphics.

For any of the options above ...

• NO spelling errors of any kind are allowed. 5% deduction (5 points out of 100) for  any spelling errors.  Grammar counts too!  Have someone proof your work!  Remember, in the "real world" of "final presentations," folks don't tolerate any grammar or spelling mistakes.

• You must include the names of each participant.

• You must clearly indicate how the work was split up and the contributions that EACH person made to the project.

How do you give us your project? BY EMAIL - no other way is accepted.

• When you email us your project, you MUST include in the SUBJECT LINE the following (and in this order):
  Your block number and your name(s)    Example:   G3/Janelle Smith & Patrick Gill

• Send your projects to YOUR TEACHER:

  • Mr. Schulenborg   merleschulenborg@msdlt.k12.in.us

  • Mrs. Weir  janweir@msdlt.k12.in.us

The Due Date: See the ChemCentral schedule.

The Rubric:

Final Thoughts:

The investigation in this experiment assumes that the volume of air used above water and below is the same.  Of course, this is not correct.  At a depth of only 10 meters, the pressure of the water on the diver's body is about 1.0 atm.  But, this is in addition to the pressure of the atmosphere itself; the total pressure on the diver is about 2.0 atm.  Under these circumstances, air will be consumed at approximately twice the rate as on the surface.  This is because the lungs will continue to expand to their normal size, regardless of the pressure.  Since the volume to which the lungs inflate remains the same, the pressure of the air from the tank will need to equal the pressure outside the lungs - in this case 2.0 atm.  Since the air is being supplied at twice the pressure, it is used up nearly twice as fast.  This can also be thought of in terms of the moles of air required at a particular pressure.