ELI5- What’s Surface Tension?
In: Chemistry
Each water molecule has a slightly negatively charged part (oxygen end) and a slightly positive part (hydrogen) because of its shape. So the delta positive hydrogen of one water molecule is attracted to the delta negative oxygen of another water molecule, called hydrogen bond. As there are so many molecules of h20 in water there are lots of hydrogen bonds, meaning a higher force is needed to break these bonds which is surface tension.
The more water you try and displace the higher this surface tension, for example you could run your hand slowly through water with little resistance, but if you try and slap the water you will be met with more resistance as you will break more hydrogen bonds with a quicker hand movement.
Surface tension is basically the tendency of molecules of a liquid to attract one another. This causes the surface of the liquid to behave as if it were an elastic membrane. In the abscence of any other forces, surface tension will cause the surface of the liquid to contract into a sphere, which is why water droplets take on a spherical shape. The effects of surface tension can be seen clearly in [this video](https://www.youtube.com/watch?v=H_qPWZbxFl8), taken on board the ISS. Another illustration is [this picture](https://www.warrenphotographic.co.uk/15106-pond-skater) of a pond skater – the water surface is deformed near the insect’s legs, a bit like it would if you were standing on a trampoline. Without the surface tension, the insect would just sink.
Liquids are made up of tiny things called molecules. To be called a liquid, a big lump of molecules needs to meet two requirements: sticking together, and being able to slide around past each other.
Surface tension is these molecules sticking together at the surface of a pool of liquid, and often causes the pool to round off its corners, forming tiny bulges and overhangs that seem to defy gravity.
Think of it like a net picking up a bundle of fish from the water. The fish are heavy and flop about, sliding past each other. If the net wasn’t there, the fish would fall out and eventually settle into a pretty much flat pile. But because of the net, the fish are held in a bugling, writhing shape.
At the surface of a liquid, the stickiness of its molecules acts like a net, holding the molecules mostly inside the main body of liquid.
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