Physical properties of water
About this video
This short video explains why water droplets form and stick the way they do. Cohesion is water sticking to itself, and adhesion is water sticking to other materials such as glass. Together they explain water climbing a paper towel, insects walking on water, and trees pulling water up from their roots.
You'll be able to
- define cohesion and adhesion with examples.
- explain how cohesion and adhesion help water move up paper and narrow tubes.
- describe a real use of water's properties, such as fog nets.
Key words
- cohesion
- Water sticking to itself, like tiny magnets.
- adhesion
- Water sticking to other materials, such as glass or paper.
- droplet
- A small ball of liquid held together by cohesion.
- fog net
- A mesh that collects water droplets from fog in dry places.
- waterproof material
- A material designed so water does not soak through or stick to it.
Transcript
water is everywhere it's in the air we breath, the clouds above us, the oceans below and even inside us. but have you really ever stopped to notice how water behaves? I mean, how exactly do those droplets form everywhere even on the spider's web? Or check this out, how can these tiny insects walk on water?
This is all due to a phenomena called cohesion. Water's ability to stick to itself like magnets. But wait, water can also stick to other things like glass that's called adhesion. You've probably seen it when water moves up a paper towel or through tiny tubes, and it's partly the reason why trees can pull water all the way from their roots to their tallest leaves But, what exactly is this cohesion and adhesion?
What causes them? And how do they cause so many beautiful phenomena? Being curious and asking these questions is the first step to doing science, because when we do understand, we can use that knowledge to create some clever solutions like waterproof materials that protect our electronics or our clothes, and even our entire homes.
We can also create lifesaving technologies like micro fluids used in medicines where water's properties help deliver drugs in precise ways. Or think about fog nets that collect water literally from the air in the driest parts of the world, making life possible in places where rainfall is scarce.
So water is everywhere. It shapes life as we know it, and without it, we wouldn't exist. Yet, it's so common that we often forget to notice the curious properties it shows us every single day. So next time you see a water droplet, take a moment to wonder, why does it behave like that?
What's really going on?
Video © Khan Academy, used under CC BY-NC-SA. Watch on Khan Academy. Puzzicle is not affiliated with Khan Academy.