Dive con

[darnallj]

WEll I am about halfway through the SSI Divecon program, Water stuff is fairly easy I jsut don't like the teachback stuff. I have to do a 15 min lecture on dalton's law saturday anyone have any insight on this

 

[ClayJar]

Insight on what, exactly? Is it the physics aspect or the instructional side that you'd like some tips on?

If you're looking for examples, one I like is using balls and their collective weight to represent gas molecules and their collective pressure:

Toss a quarter pound of marbles and a quarter pound of pinballs into a bowl, and tada! You have half a pound, total, of 50% marbles. Mix half a pound of 50% marbles and half a pound of 100% marbles, and what do you have? (Basically, the concept goes like that, and you can separate them out and weigh them to verify the results.)​

By turning something that is mysterious and invisible (gases following Dalton's Law) and turning it into something simple and concrete (balls and weight), you can give people something to connect. Of course, there's still all those fractional numbers, percentages, and decimal points, but that's another presentation.

Incidentally, did you just get assigned the lecture? I thought usually people were given much more time than that to prepare, as developing a lesson plan, teaching notes, and any training aids isn't exactly something that's best done overnight. Sure, it's just one 15-minute lecture on an elementary topic, but surely you'd need at least enough time to practice in front of a mirror.

(On the other hand, I guess you could develop the lesson tonight, practice tomorrow night, and deliver it Saturday... I'm glad we're given more advance notice than that for our first lessons.)


(Actually, if you used marbles and something else that doesn't roll, you can probably separate out the bits a lot more easily. You just dump the bowl onto a slightly sloped tray, "drain" the marbles, and scoop the rest up. If you had many hundred dice, that would work well, but I doubt most people have the functional dice collection I do. :biggrin

 

[darnallj]

Yes the instructional side I understand the physics side fairly well.

Yes I was assigned this topic Last night for Saturday I have made a powerpoint presentation and in it I have three Gas molecules drawn out one for Surface, then 33ft and 66ft. And then inside those I show the actual nitrogen molecules and oxygen mlecules in each gas molecule. and how if you take the pressure you are under say 2 atm or 33 ft how to figure out what percentage the O2 occupied and much the Nitrogen occupied.

 

[ClayJar]

Yes I was assigned this topic Last night for Saturday I have made a powerpoint presentation and in it I have three Gas molecules drawn out one for Surface, then 33ft and 66ft. And then inside those I show the actual nitrogen molecules and oxygen mlecules in each gas molecule. and how if you take the pressure you are under say 2 atm or 33 ft how to figure out what percentage the O2 occupied and much the Nitrogen occupied.

I know you were just summarizing what's in the PowerPoint presentation, but you allow me to bring up an important point. When teaching, it is very important that you be clear, that you be correct, and that you be consistent.

You have confused me with "gas molecules". The molecules in air and nitrox (ignoring argon and the trace gases) are oxygen (O₂) and nitrogen (N₂). Obviously, you've got that down, but what are the "gas molecules" that you're showing oxygen and nitrogen inside? If they're just gas bubbles, pockets of gas, containers, or whatever, it is important not to call those "molecules", since a "molecule" is a well-defined thing (O₂, N₂, CO₂, et cetera). If you use the word "molecule" in some other meaning, you would be saying something that is not correct. Even if you had an alternate meaning of the word "molecule", using two meanings is not consistent, and inconsistency strongly impairs learning.

I'm also confused by the part, "...what percentage the O2 occupied and much the Nitrogen occupied." (Again, this may just be your summary; your presentation may be perfect, but I have only the summary on which to comment.) Are you asking about what fraction of the gas is oxygen versus nitrogen? Are you asking about pressures? "Occupied" is a word that's used with *volume*, which is a completely different thing than either of those. Each gas occupies the same volume, i.e. that of the "bubble". (I'm ignoring such concepts as "mean free path" and the like, as they aren't relevant and are outside the scope of dive classes.) It takes extra effort to be perfectly clear, but it makes learning that much easier.

I hope you don't take this as me disapproving of everything. Far from it! I'm just trying to point out a few fairly easily correctable things that were in your summary in order to give you a better shot at avoiding some of the bigger pitfalls that end up catching most all of us early on. If you can learn from my mistakes, you might not end up making all of them. :biggrin:

(Of course, no matter how good you end up being, there's always something that trips you up when you're doing these. Do your best, and be glad it's not broadcast to the world like American Idol tryouts. )

 

[darnallj]

LOL on american Idol, Yes wording of molecules in the last mesage wasn't the best what I did was take and drew a ballon on power point and then drew bubbles perse inside the ballon and colored them different I drew 8 bubbles of nitrogen and 2 for oxygen, then showed how to calculate that nitrogen made up 11.76 psi of the total 14.7 on the surface and oxygen made up the rest, then i duplicated that image except for incrasing the number of bubble inside the ballon to 16 and 4 to show how the nitrogen would still occupy 80% of the total volume of 29.4 psi since you would be at 33ft then done the same for 66ft. I sent the powerpoint into one of the instructors of the class and he thought it looked fine.

Thanks for your input on wording. appreciate any and all help as I am not a great speaker or teacher I can do the skills and help ppl with skills but relaying the actaul techinical info in calss is my biggest weakness.

Any thoughts on say an attention getter to start off the talk and then, They like us to give each topic a value of importance, I was going to tie in the value with the importance of understanding the law and breathing compressed gas and the risks of nitrogen narcosis and oxygen toxicity.

 

[tstormdiver]

This is probably kinda vague & may not help too much, but form my recent Dive Con course,try to be thorough on your subject, but keep it simple. You have to remember that you're supposed to be lecturing to beginners in your presentation. Most will have essentially, no clue of how these laws work. Don't overwhelm with big terms & too many numbers. To be honest,I did not have that subject myself during my training, but the one that did, got so involved & way too deep (with even some inaccurate info) that he had everyone scratching their heads. He even had the instructors confused. A few visual aides can certainly help with the understanding, but like I said earlier, just try to keep it as simple as possible & should do OK. Good luck to you.

 

[AzAtty]

If you had many hundred dice, that would work well, but I doubt most people have the functional dice collection I do. :biggrin

Aha! An RPG geek! I knew it!

 

[ClayJar]

Aha! An RPG geek! I knew it!

Actually, I've never once played a paper-and-dice RPG. Other than one complete RPG-style set I bought to entertainingly make up dive table questions, all I have is a breadbox (hehe) full of D6 dice and a Boggle box (go figure) of D12 dice, all of which are used for odd custom games.

Hehe, in other words, I'm even *more* odd than your standard RPG geek!

(Oh, Mom *did* give me a set of brass dice for Christmas... which ought to be fun when they show up on a platform in a quarry somewhere... )

 

[AzAtty]

My second guess would be a craps nut, but they don't rattle D12s.

 

[Kevfin]

PowerPoints are nice. I have them them for SSI. They help keep you on topic, can prevent you from missing important points, and help the subject matter move along. I haven't found an OW student that likes a 2 hour lecture on gas laws (if there was one, they didn't say).

Ah, but the catch is that PowerPoints can make a dry subject even more dry. I'd suggest not focusing on your own presentation. Don't just look at and read the Power Point. Look-up and around, smile, breath, pause, vary the pace of your presentation. Can be hard to do if you're feeling anxious...

Most SSI shops also like when you sell gear during a presentation. Even if done subtly. When lecturing about gas laws, it's a good time to mention computers/bottom timers etc. and how they help with ascent rates, nitrogen loading, or whatever (specially for new divers)... just do your best to keep it simple.

The DiveCon book covers Dalton's law pretty good. So you have all of the basic info you need.
I'm sure you will do fine. Have fun with it (if you can).

All the best,

K

Here is some lame humor you could try prior to your lecture, to lighten things up:

You know your buddy hates you when:
a. He gives you the "wait here" sign and you are still on the boat?
b. He "forgets" to close your dry suit zipper?
c. You give him the out of air signal and he passes you his snorkel.
d. When you indicate you are low on air, he writes on his slate "I'll get you some" and swims off?
e. You give him the "OK" signal and he gives you the finger?
f. He spits in your mask for you, but you haven't taken it off yet?