let's talk about one of the most amazing forces in nature capillary action now without capillary reaction you would be dead and everything else in the world would be as well so this is awesome let's cover the basics what it is i have a capillary tube set here and we're going to show you why trees are awesome capillary action is the ability of a liquid to flow against gravity up a narrow cube now this is a combination of actually two different forces cohesive forces which is the attraction between molecules in a liquid and adhesive forces the attraction between the liquid and the surface of the tube now it doesn't have to be in a tube specifically but in this example we will be using cubes if the adhesive forces are stronger the liquid will rise what does that mean well that means that if you have a very very small tube water will actually rise against gravity and not just water liquid in itself so i have a capillary tube set here and we're going to be playing with that and we're going to be talking about trees but first i want to show you what happens when i pour a liquid into a container look what happens it flows downwards because of gravity into the other container and it stays there that is the level at which it reaches equilibrium and that is a flat plane this is a capillary tube set we have four different tubes of different sizes this one's fairly large this one's smaller smaller still and absolutely tiny so let's pour it in here and we'll see actually let's zoom in there we go all right i'm going to pour this in very slowly as we pour it in let's watch what happens to the other tubes okay capillary action in its most basic form is water is sticky liquids are sticky they want to stick to things on a molecular level they want to stick to things so badly they're actually willing to fight gravity upwards as they stick higher and higher and higher the larger the relative surface area is to the liquid ratio the stronger this capillary effect is what does that mean that means just the smaller the diameter of the tube the higher the water is going to be able to get up the tube all right so as we see here we have this is our baseline this is where water is going to be at a natural pressure right now that is the equal amount pressure from the atmosphere and pressure from the liquid as we move across the pressure is the same all the way down but as we move up each tube has a different height of the liquid this is actually a lower pressure anything above this line is a lower pressure than the atmosphere itself it's fighting gravity so much it's actually lowering its pressure now this is why there's a limit to how tall capillary action can be because if you lower the pressure of a liquid just like this liquid is doing here as using capillary action to lower its own pressure to rise up the tube the lower the pressure is the lower the boiling point of that liquid is so as this gets lower and lower pressure all the way up eventually it's going to boil spontaneously in normal temperatures approximately that level is 30 feet or 10 meters anything any tube that is longer than 30 feet or 10 meters will have need such a low pressure in order to either suck it up if you're using a really really long straw or a capillary action tube the pressure will be so low the water just boils away and it doesn't exist anymore that's very cool that's capillary action the basics but how do trees use capillary action okay so you might remember when you've learned about trees in your science books that trees use capillary action to whisk water around from the ground up through the trunk into their branches and leaves and then that kind of fuels photosynthesis etc etc that is true but also impossible because remember trees are taller than 30 feet tall some of them so how do they get around the absolute laws of physics where the height of the tube inside of these trees actually dictates that the water should be boiling long before it gets to the top of the trees and into the leaves so how does this work well trees are so cool what they actually do is they create negative pressure they create negative up to 15 atmospheres of pressure at the top of the tree so how does that work you can't get below a vacuum can you ah yes you can you can't get lower than a vacuum in gases but you can get much lower pressures in liquids and solids so in solids we would see this as tension so there's i'm tensioning this balloon far beyond negative one atmosphere of pressure well the same thing works with solids so when a tree creates negative 15 atmospheres of pressure at the top of the tree it's using capillary action to whisk up in minuscule little tubes water from the bottom all the way to the tippy top of the trees now why doesn't it boil it's because trees are nearly perfect tubes that have never had anything except for water in them what does that mean well that means that there's no nucleation point for the water to boil so just like a super saturated solution or a super chilled bottle of water where it's not going to freeze until you give it a jolt and turn it into ice so too does the water not boil in a tree because there's no nucleation point there's no air bubbles in those little tiny tubes running through a tree so that's so amazingly cool there is an awesome video done by veritasium a long long time ago i think that really explains the tree aspect of this better than i can so go check it out this is destructive creativity i hope you enjoyed see you next time bye [Music] you