Science Moms Guide to Water Part 3 Capillary Action

We expect water to move downhill. After all, rain falls down from the sky and rivers flow downhill to the ocean. But water can move uphill too. I'll show you with a paper towel. I dip just the bottom edge of this paper towel in water and in just a few seconds the entire paper towel is wet. Water traveled uphill against the force of gravity. How is this possible? Capillary action. Capillary action is very important for moving fluid in our bodies. Have you ever heard of capillaries? Those super small parts of your circulatory system? They would not work without capillary action. It's also important in plants for moving water from the roots up to the leaves, and in geology. Capillary action plays a big role in weathering and frost wedging. In this video we're going to do four fun activities that explore how water moves, both through capillary action and siphons. In our first activity I'll prove to you that black ink is not really black. To set it up, I draw a line on a paper towel with a marker. Then I arranged the towel so that only the very bottom of the towel will get wet, making sure that the marker line is above the level where the water will be. As soon as the paper towel gets wet, you can see the water traveling up the towel. And look what happens to the ink. It's moving too! This takes several minutes, so will speed up the video so you can get a better look. And check that out! You can see that what looked like black ink was actually a mixture of pink, blue, and yellow dyes. Here's how it worked: when the water travels up the paper towel, it can carry other things with it, like the dyes in the marker ink. Some of the dyes are smaller and they travel faster. Other dyes are bigger and they travel a little slower, and that's why we get the separation of the colors from the black ink. Let's do this activity again, but this time we'll write a message using different markers on the paper towel [music] Isn't it fantastic that what started out looking like that, ended up looking like this? You can have a lot of fun by trying different types of paper and markers. Here's the same marker on a paper towel a Kleenex and a coffee filter. And here are several different types of markers on paper towels. Notice how the permanent marker doesn't change at all. You can use colored markers too. But whatever marker or paper you use, be sure that the line of ink stays above the water. In our second activity we're going to move the water in these cups just using paper towels. This is one that takes a little while, depending on the size of the cups and how much paper towel you use, the temperature of the water, the time can vary a lot. So once I get these set up I'm going to speed up the view so you get to watch it in fast motion. [music] You can use any size of cup for this investigation, and if you didn't have paper towels, you could use cloth or even pieces of string. Sometimes the water mixes right away and other times the water will be layered with one color being on top of the other one for a while. But if you wait long enough, the water level will become completely even between all the cups and the colors will be fully mixed as well. To understand why this works, you need to realize that small spaces do not function the same way as big spaces. This is something we know intuitively. We're not surprised when ants carry seeds that are 100 times heavier than they are. But we would be very surprised if a person carried a fully loaded semi truck. It's not possible. Are ants stronger than humans? No. They're smaller. If a person could be shrunk down to the size of an ant and still be functioning alright, They'd be able to pick up an ant-sized semi trailer with no problem. Size matters. And the rules for how things move and behave change depending on the scale. The best example of this is quantum physics. At the quantum level, things get really bizarre. You have particles that can pop in and out of existence. Hello. Goodbye. Things can exist in two places at the same time. I'm in two places at once! That shouldn't be possible! And you have particles that change how they behave based on whether or not their being watched. I'm a wave. Now I'm a particle. It's fascinating and incredible but to understand it, you need a lot of math. So keep up your math practice, and one day you might be lucky enough to take a course in physical chemistry or particle physics and get to learn more about bosons and quarks and neutrinos and the mysteries of quantum mechanics. Buy we don't need to go down to the quantum level to understand capillary action This property of water takes effect when we're on the scale of molecules to millimeters. At this scale water can travel any direction regardless of where gravity is telling it to go. But it will only do so if it has adhesion. If you had a small space that was oily and hydrophobic, then the water would not move up it and you would not have any capillary action. But the fact of the matter is, most of the world likes water. Water has good adhesion with rocks, glass, plastic, and of course, paper towels. And paper towels are full of small spaces, both in between the layers and fibers of the towel, and in between the cellulose molecules that make up the paper towel, That is why they're so absorbent. So that explains how water went up the paper towel in chromatography, and how water traveled from cup to cup in the walking water experiment. But why did the water level end up being completely even across our cups? It's because we just made a siphon! And we'll do it again in our next activity. Humans have been using siphons to move water for thousands of years, and if you ask most people how they can get water out of this big container without tipping it over, they'll say, well, get a tube and suck on it to get the air out, and then, you know, bend the tube and the water will come out. Something like this. Bleach It works well, but it's a bit messy, and you might not want to get a mouthful of the water that you're trying to move, So let me show you a better way. To make a staw siphon, all you need is a bendable drinking straw. If you put the drinking straw into the cup of water like this, nothing will happen. But, if you cap your finger over the top first and then let go, something will. Here's why: Watch, if I cap my finger over this end and put the straw in the water, most of the straw is still full of air. And when I let go, water will shoot up. Did you see that? So now, if I put my finger over the top and place the straw all the way down to the edge, When I let go, the momentum of the water should carry it up and over and start my siphon. There we go! We have a siphon! I want you to make a prediction. Do you think that this straw is going to empty ALL of the water out of the big cup, and make a huge mess over my table, Or do you think it will stop part way through? If you think it will stop, tell me when and where. Where do you think the water level will drop to before the siphon stops. Pause the video. Make a prediction. And then start it again to find out. And, do you hear the change? The water is going slower now, and pretty soon it will start to drip. Ah! There it goes! And, now it's stopped. As long as the straw allowed the water to move from higher elevation to lower, the water was flowing. But as soon as the levels became equal, then there was no reason for the water to travel up and through the straw. Here's another way to think of it. If I have two cups with the same amount of water, then the amount of water in the tubing is equal. There's no reason for it to flow from one cup to the other cup. But look what happens when we change the elevation. Now the sides are no longer balanced. One part of the tubing has much more water in it than the other, and that greater weight is what drives the siphon. [music] Our last activity is fountain in a bottle. I drilled two holes into the lid of this bottle and then I put tubing through and secured it with duct tape so that it would be airtight. I have one end going to my fill cup here, and the other end going down here to a drainage cup. And all I need to do to start the fountain is flip it over. Watch this. See the blue water coming down the line? And now the fountain is working! The fountain will keep running as long as we have water in our fill cup, or until I flip the bottle back over, whichever comes first. If you flip it over, it becomes kind of a dribble fountain, and it will keep going as long as this level is lower than the fill cup. But if you get that level higher than the full cup then, of course, it will stop. And that's the fountain in the bottle. Don't forget to print out your science coloring book that goes along with this video. It has instructions for all of the activities that we just did and you can find it for free at my website, available in several different paper sizes. And our brave books that provided the elevation change in the siphon experiment are the book recommendation for this month. These are Nathan Hale's Hazardous Tales, and they are fantastic. They go through real U.S. history events with a narrator who time travels and takes you back to see what really happened in history. So check these out. My kids love them. I love them. They're really well done. And that's it! Work hard, grow smart, I'll see you next time. The momentum of the water shooting up will carry it over Oh! you're kidding me. Wa wa waaaaah! It didn't work. Cap it. Make SURE that you don't let your get wiggly. Pause the video? what do you need? (soft voice of child telling on sibling) Oooh. (Sibling): "It was an accident!" And then you've got to get water in this tube, so I'll suck it in, Blegh! And if you don't tip the tube enough, it stops! Oh that tasted bad. Like plastic. It looks kind of the Starship Enterprise. I like it. [singing] Siphon. Siphon. My voice will sound like a chipmunk when I speed it up. [chipmunk voice] Siphon, siphon. My voice will sound like a chipmunk when I speed it up!