00:02
Hi there.
00:03
To answer this question, we need to talk about a few terms.
00:07
One of these terms is cohesion, and cohesion are forces of attraction between like molecules.
00:33
For example, water molecules being attracted to other water molecules.
00:50
So water molecules to water molecules.
00:52
Another term is adhesion.
00:59
Adhesion refers to forces of attraction between different molecules.
01:26
For example, in this case, water molecules to the molecules of the glass in the tubing.
01:40
And there's yet another term that i want to add here, and that is surface tension.
01:47
Surface tension we particularly see in water, and that is the stronger attraction of water to itself at the surface.
02:02
And that's due to an imbalance in forces.
02:09
I'll describe that just a second.
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So the water almost acts like it has a thin skin on it.
02:16
A little water bugs can walk on it.
02:19
If you're careful, you can float a paper clip on it.
02:21
That's because of surface tension.
02:24
And as i mentioned, it's due to an imbalance of forces.
02:27
So we have water molecules attracted to other water molecules.
02:32
And typically, if you are within the water, these forces of attraction occur in all directions.
02:40
But at the surface, they can only be directed downward and to each side because there's no water above them.
02:51
So we have this imbalance of forces where the water molecules are attracted downward and laterally, but not upward.
02:59
So that ends up giving us a little bit stronger attraction there at the surface.
03:03
All right, so with these terms in mind, let's talk about the capillary tube.
03:10
So here's our capillary tube.
03:18
Let's talk about the forces at work.
03:21
We have water molecules that are attracted to each other.
03:29
At the surface, they're attracted even a little more strongly...