Claire Corlett

Fish Food, Fish Tanks, and More
Science Spotlight: Fish, Swim Bladders and Boyle’s Law

Science Spotlight: Fish, Swim Bladders and Boyle’s Law


Ok, so today I’m using this balloon to
simulate the swim bladder of a fish and I’ve also got some weights attached to
it. So, these are sort of simulating the
weight of the fish that normally would drag it down and an artificial swim bladder that’s filled with gas, so that it would keep it neutrally boyant.
So, what we’re going to do is place it inside of this canister and slowly
increase the pressure. Ready? So, I’m gonna screw this on and we seal it up, so that we can increase the pressure. Make sure it’s nice and tight. Got
everything all connected now, so I’m going to flip on the pump. Shut our
bleed valve, and you can see water going in right now. Because there’s not a
whole lot of pressure on the gas inside that balloon, it takes up a lot of volume. It’s
basically displacing water and, by doing that, it increases its boyancy. So, the pressure in here is starting to decrease the volume enough inside that balloon that we can
see it sink. Ok, so we’re at about 50 psi right now
which, according to the Coca-Cola company, is how much pressure is inside of a can
of Coca-Cola in a room temperature room. It is equivalent to diving down about a
110 feet under the ocean. 15 psi is atmospheric pressure at sea
level. And you can see that the balloon has shrunk quite a bit. When it went in,
it was about the size of a tennis ball, now it’s about the size of a ping-pong
ball or so. And, if I continue to increase the pressure, it will get even smaller. So, the gas inside the balloon is being
pressurized. So, what Boyle’s law tells us is that, as
you increase the pressure on a gas, the volume decreases. And also as you decrease the pressure,
the volume of a gas increases. That’s because the atoms of the
molecules inside the gases have space between them, and as you increase the
pressure — those atoms and molecules get closer together and so they occupy
less volume or less space. Still the same number of molecules in
there but what happened was the molecules get closer because of greater
pressure, and so the volume decreases. So, now what I’m going to do is release all
the pressure that’s inside here, and the volume of the gas is gonna increase —
and you can see it floats right back up to the surface.

9 comments on “Science Spotlight: Fish, Swim Bladders and Boyle’s Law

  1. this video was recommended on school house teachers and i think it is a great way of explaining a fishes swim bladder. thank you!

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