Intro: Water Drop Science: 8 Explorations
Water you waiting for? There's an ocean of knowledge and experience lying in every wee drop water, and it's now you can start checking it out. From looking at surface tension to magnifying effects to vapor cushions, the water drop makes being little seem like a pretty big deal. I love doing these explorations with my students, and each one is a take-off point for more.
Water Drop Science: 8 Explorations is a way to dive into water drops like you never have before. If you have some other water drop experiments that you love, share them in the comments. H2Okay, let's go!
Step 1: Leidenfrost Drops
A hot drop on the right surface will start to boogie. Heat up a metal spoon over a stove or any other flame, and once it is very hot, squeeze out a couple water droplets. The drops will collect and remain in a surprisingly orb-like shape and dance around the metal spoon even after you've taken it off of direct heat. Play around with the temperatures, shapes, and ways that you heat the spoon to get massively different effects. Of course, be careful when dealing with hot things!
This all happens because of something called the Leidenfrost Effect where a liquid when in contact with a surface much hotter than its boiling point, produces a vaporized layer creating a buffer between the surface and the drop. It's like a water drop hovercraft! Additionally, with special heated surfaces, you can even get water to "climb uphill" as you can see in this Leidenfrost Maze.
Step 2: Water Lenses
Drop a few water drops on to a mirror to get a fascinating lens effect looking back at you. You'll see your face in each one of the drops on the mirror. but with the image flipped upside down. These actually work like any other lens, including our own eye, where the light coming in gets refracted and projects upside-down which means our brain is doing the flipping. See how many you can fit! For more information on lenses, start with this!
Step 3: Penny Blobs (surface Tension)
See how big you can make your penny blobs before they spill over (44 drops for one of them!). Besides giving all of your pennies bulging hats, you're exploring surface tension, which is the nature of liquids to try to reduce surface area by sticking together with adhesion. You can fit a bunch of drops on the head of a penny, even beyond what you'd think!
Try the experiment out with other liquids such as milk, oil, water with salt, and water with soap, and you'll find you get different results with how many drops a penny can take. It turns out that water has a relatively high surface tension compared to other liquids, which means other liquids don't make it as long before they run off the side. Try it out, count your drops, and clean up those micro-messes after!
Step 4: Water Drop Macro Lens
With a dab of water on your phone's camera, you can suddenly create a macro lens for some up-close magnifying photography. This is kind of like the water mirror lenses, but now we can see through from the other side, and you can use this to explore quite a bit in nature. Dab a little bit of water over a phone camera, and click away to get some neat photos. Try fingerprints, leaves, and clothing to get a start on your new world of macro photography!
This is due to the convex nature of water drops, which bend light such that objects will appear larger in the camera than they truly are. Play around, and see what you can discover in your world when you look up close.
Step 5: Life in a Drop
A drop of water can be like a little world when it comes to microfauna. Drop a cup of water with weights into the ocean, a river, a lake, a pond, or a puddle, and pull it out to get a sample of the local water. Often the closer to the base sediment you get, the more it will be teeming with visible life.
After you scoop it up, drop a bit of it on a mirror, and take out your handy-dandy laser. Get in a dark area, and shine your laser through the drop of water, which will act like a projector displaying the shadows of any life that go by. I found some zooplankton! What will you find in yours?
Step 6: Accordian Snake (capillary Action)
This one is a fast-food special. Scrunch up your straw wrapper on the straw, and then nudge it off one of the ends. It sits there compressed, until you begin dropping water on it, and then HUZZAH! A serpent grows!
This is from something called capillary action. When water hits the snake, it begins to spread throughout the paper due to water being attracted to oppositely charged molecules in the paper. As it spreads, due to adhesion, it takes other drops with it until the straw wrapper is wholly soaked. As the fibers absorb the water, the wrapper acts like a sponge, and grows as it twists and turns in front of you.
Step 7: Drops on Leaves
See how nature deals with the wet stuff! Many plant leaves are extremely hydrophobic, which means they repel water. This has to do with their structure, and namely something called the contact angle of the water drop and the leaf itself. Drop water on different parts of a plant, and you'll find different it acts in different ways. A common trait for broad leaves is that water drops form into beads.
We are still not fully sure as to why there is a prevalence of hydrophobic leaves in nature, but many believe that it is to help clean the leaves of dirt and would-be invading microbes. This also keeps them from getting damp, which would provide a host area for molds and other organisms as well. The plant most famous for its hydrophobia is the lotus plant, being the namesake of the lotus effect.
Wander around and test some leaves, and then you can see what they look like up close, and how humans have engineered materials and chemicals to have similar hydrophobic tendencies. This is also a place where you can see many examples of the water drop lens effect in nature.
Step 8: Water Drop Trampoline
With a little bit of laminar air flow, you can get water drops to hop around! Make a fistful of straws with skinny straws in the middle and wider straws on the outside, and put them in a mailing tube. Tape the tube to a blowdryer, and run it on cool. After stabilizing it and turning it on, you'll find that you can drop water and have them bounce up and down for a bit before falling off and being ripped apart.
The water drop trampoline relies a lot on pressure, the Bernoulli principle, laminar flow, and water's adhesion, which is quite amazing when you think about it. if you want a full Instructable on how to make this, check mine out here!
I'm excited to hear what other experiments and explorations you do with water drops! Share them in the comments below and I'll try to add some in as we go! Have fun and keep exploring.