Can a Boat Float In Supercritical Fluid? (Stabilized Version)

this is liquid CO2 right before it reaches its super critical point the most fascinating part about watching a liquid turn Super critical for me is that before the Super critical point there's obviously a liquid below with a gas above separated by a line or a meniscus but once it turns Super critical that line just kind of Fades away and it becomes one state a super critical fluid but this gave me an idea and raised a question in my mind if the line just kind of goes away then what would happen if there was a boat floating on the surface of the liquid right when it turns Super critical what happens to the boat does it just stay right where it was floating before or would it now float to the top since the whole tank is now filled or would it sink to the bottom because there's no layer of liquid to float on well today I'm going to be testing this out by actually floating a small styrofoam boat in liquid CO2 and then heating it to its super critical point in order to do this I have to contain a lot of pressure the super critical point of CO2 is at 73 atmosphere which means I need to contain over 1,000 lb per square in in my vessel so to do that I'm going to be using this vessel here it has two thick pieces of acrylic windows and I can bolt these together over the body that has a valve and a pressure gauge right here this tank has been tested to over twice the pressure that I'm going to get to today but it still makes me a little nervous using it getting to this high of a pressure so to start off we need some CO2 when it's solid we call this dry ice so I'll just just grab some chunks of dry ice and put it in the vessel now I'll tighten these bolts and then close the valve as soon as the pressure increases the dry ice stops turning from a solid directly into a gas oh there it goes but it can now turn into a liquid so now we've got liquid CO2 in here if I release the pressure it freezes into solid CO2 again okay so now let's do this for for real let's put in our dry ice and I'm going to add this half sphere of Styrofoam to act as our boat floating in the liquid okay now let's put our little boat [Music] in let's close it up okay this styrofoam is very squished but it is floating okay now I'm heating it up see if we can get to Super critical pressure here it'll be at around 1,00 PSI okay we're above 500 PSI we're about halfway there and see there's still the meniscus there it's not even cold anymore we're getting close okay right now we're at 68° F we're waiting to get to around 87° f look how the fluid splashes we're getting very close to the super critical State okay here it goes going to wiggle it a little bit see what it looks like whoa what is happening it's like dripping from the top it's condensing and dripping down look at [Music] that it's like a waterfall that is so weird that means it's super critical on the right side but then it's condensing back into a liquid on the left side cuz the right side is where my heat is so what's happening is the refractive index of the gas and the liquid are becoming the same and so you don't see a meniscus or you don't see the light Bend when it goes through the [Music] liquid even when I shake it you don't see a real difference difference between the refractive indices but you can still see the styrofoam floating on top uh-oh the styrofoam is dipping deeper down in it [Music] now wo it's like disappearing look the line's disappearing that meniscus is just going away but the styrofoam staying pretty similar place to where it was [Music] okay the line is literally going away you can still see it disrupt the background though in this shot so there's still slight meniscus [Music] there but it's going away W and it's kind of rising up above the surface of the styrofoam oh the styrofoam sunk it sunk down in the [Music] liquid but now I can no longer see a meniscus on top you can't really tell where the gas and the liquid separate from each other okay it's fully super critical now over 1,000 PSI now and the styrofoam is at the bottom you can still see that it's being heated from the side there so you can see some little waves happening from the hot fluid Rising but it's all super critical there's no meniscus whatsoever if I pick up the vessel and move it around you can see that there isn't two states in here anymore it's just one state that's a little viscous and the styrofoam can just fall through it slowly [Music] okay now let's let it cool down a bit and it should revert from its super critical State into a liquid with gas above it again and I think the styrofoam should float once again okay I'm going to put an ice cube on top oh it disappears from view gone oh there it is I saw it start to float and it's back on top look at that as soon as it's out of the super critical phase then it floats back on top of the meniscus that is so cool totally back on top okay now I'm going to release the the pressure okay 3 2 1 whoa the styrofoam got sucked out the little tiny hole there tried to leave here's our styrofoam boat it survived that's where it tried to get sucked out of that little hole at the end so why did this boat sink when it went super critical well if you think about it right before it turns Super critical there's a liquid on bottom and a gas on top since the boat is floating right on the surface of the meniscus that means the average density of the boat is more dense than the gas but less dense than the liquid but then once it becomes super critical these two states suddenly become one so it would make sense that the density of the remaining fluid should be some average of these two states and sure enough if you look up the density of liquid CO2 it's around 800 G per liter at room temperature but then once it reaches its critical point it suddenly drops to just above 400 G per liter this average density is less dense than the boat's average density so it sinks to the bottom this would also be the case with any real boat that had an open top as well so there we go now we know that boats sink in super critical fluids so next time you're on a lake that suddenly Turns Super critical be sure to get to shore quickly for more practical tips like this be sure to subscribe to my channel if you you haven't yet and we'll see you next time

Channel: Action Lab Shorts

Views: 42,112

Keywords: Science, carbon dioxide, supercritical co2, supercritical fluid, pressure vessel

Id: acFkZiELN2g

Length: 9min 12sec (552 seconds)

Published: Fri May 24 2024