Science Buddies: "Ask an Expert"

Hello everyone,

I hope to answer the question of How does the chemical composition of a pool affect your speed?
Being an elite swimmer, I find that many competitive pools use different chemical treatments for their water. I also feel like some make the water thinner, or less dense, than others, which could lead to faster movement through the water, no? I need help finding general chemical compositions for pools and maybe compositions for competitive ones too. I am open to any suggestion to improve on my project. Every answer helps!

That is a really interesting question and observation! All of my children swam competitively and we never thought about that one!!! We knew the temperature of the water had something to do with their times - but we attributed that to their muscles being tight or relaxed - when in fact I should have realized that temperature of water also affects its density. Do you notice that in different pools your times are better or worse depending on the temp of the water? Indoors? outdoors? Do you think maybe temperature of pools might be an easier variable to test?

Your idea is a good one, though you'd have to get water samples from the pools and the chemical reports to compare each of the pool's water composition.
Then, how will you determine the effect on swimmer's times? There are too many variables to use human subjects to test times, so you'd have to design an experiment to test the speed at which an object moves through each of the water samples.

It's a really interesting idea! Imagine what your findings might suggest?

Keep us posted - and good luck!

Hi MDG,

I second Yvette's post--cool project! Like her i knew that water temperature really affects how well i swim unless i've just run a couple miles and am really warmed up. I just swim for fun and exercise so wouldn't notice density as a factor.

Finding the composition of the water in a specific pool may not be so easy, but finding the density is. All you need is a 25 or 50 ml volumetric flask and an electronic scale that has a sensitivity of 1 milligram (0.001 g) or better. Most high school labs have one of these. First weigh the flask empty and zero the balance with the flask on it. Now fill the flask with pool water so that the meniscus falls exactly on the line. If you haven't had chemistry 101 yet then this will tell you what a meniscus is and why you need to use it: http://chemistry.about.com/od/chemistry ... -Flask.htm

Now weigh the flask with the water and record the weight in your lab notebook. If you used a 50 ml flask then the weight of the water should be very close to 50 g because one milliliter of water (one cubic centimeter) weighs exactly 1.00000 g at a temperature of 21C. To get the density, divide your weight by 50. Say your weight turned out to be 50.4 g, then the density of your pool water would be 1.008. For comparison, also measure the density of your home water, some bottled water, distilled water, or even ocean water. Record all this in you notebook along with an explanation of what you are doing and why.

There's another factor besides density that might affect your swimming ability and that's water resistance: http://www.usaswimming.org/ViewMiscArti ... temId=5004

I would bet that certain chemicals can alter the frictional drag of the water or how it sticks to the swimmer's body. I don't know if anyone has studied this, but I think it would make a great project. I don't know how you would measure water 'resistance'--probably with some very expensive machine. Maybe you can come up with a simpler, cheaper way.

Keep posting to this same thread.

All the best,

Sybee

Thanks for the replies guys, you both raise some good and interesting points. As it was pointed out, a human subject would involve too many variables, so what if i timed how long it took for something such as a sinker or weight to hit the bottom of a preset depth, then compared it to the chemicals,temperature, and location of the pool? It's cheap, and i can use a lot of places to test it.

I have to defer to those who might now more about the physics involved here.
My experience is in biology - but what I think you should choice one variable you are testing.. either the chemical composition of the water or the temperature. Once you choose ONE - then all other factors must be held constant - depth of water, place in the pool (we all know the reason the fastest swimmers are seeded for those middle lanes etc... everything EXCEPT for the ONE thing you are testing.

I'm really interested to find out what what you discover - since I always heard talk of 'fast pools' and 'slow pools' !

good luck!

Thanks for the help Yvette, I really appreciate it. I think I will compare the differences in chemical composition. Speaking of which, are there any kits or equipment that can be used to test for chemicals used in pools? And second, do you think I would need permission to take water from a public pool?

From my experience being around pools - I think you could ask the pool staff for their chemical reports? Maybe you can get some more guidance from the pool managers you are considering using.

Good luck!

A fine range hydrometer is another way to measure pool water density. Either way you will need to make all of your measurements at the same temperature or at least record the temperature and correct for temperature differences later. Pool water is tested constantly, so discovering the composition may be as easy as befriending the guy or gal who adds chemicals and tests the samples.

Cheers,
Colin