How to walk on water!

In Chemistry, Physics by Mystifact

‘How to walk on water’… impossible, right? I mean, if you could walk on water, at least you are able to guarantee you have impressed your crush. Is there a way to genuinely be able to, and if not, could we bend the rules a bit to still manage to put a smile on her face? 

Properties of Liquids

We need to understand a couple of properties of liquids; viscosity, surface tension and cohesion – to find out how we can potentially overcome the problem of walking on water.

Viscosity

Viscosity is simply a measure of how thick a liquid is [1]. The higher the viscosity, the thicker the liquid. Ketchup is more viscous than water, for example.

Surface Tension

Surface tension is the force created due to molecules on the surface of an object being attracted to each other; in our case, this ‘object’ is water [2]. The attraction of like molecules is known as cohesion. In our example this is the attraction of water molecules. This will all make more sense by the end of this article.

How do insects run across water?

In case you didn’t know, some insects are capable of running on water; but how? It is time to apply what we now know about surface tension. When an insect light enough steps on a body of water, the forces due to cohesion of water molecules are larger than the weight of the insect itself. This means the surface of this water remains intact with the insect standing on it thus allowing for some of them to walk on water as effortlessly as they do on land!

So, why can’t humans walk on water?

Humans are so big and heavy, that the force they impose on the water once they stand on it is a lot larger than the force of surface tension mentioned above. Hence, the human sinks and has no chance of being able to walk on the surface of water. So, how can humans walk on water? Is there even any way having said all that?

Non-Newtonian fluids

We are all aware that matter can exist as a solidliquid, or gas – but what if matter can behave as more than one state at the same time.

What is a Non-Newtonian fluid?

These are substances that don’t behave like we expect them to. Newtonian fluids have a constant viscosity (recall definition of viscosity above). This is not the case with Non-Newtonian fluids [3].

Depending on varying forces or pressures applied to them; Non-Newtonian fluids flow at different rates. An example of a Non-Newtonian fluid would be ‘Oobleck‘ which can be made in the comfort of your own kitchen!

How to make Oobleck

All you need to do is have some water in a container of your choice, and slowly add cornstarch a bit at a time whilst stirring. Keep doing this until the solution goes gooey and hopefully, you have made your first ever Non-Newtonian fluid!

What relevance does this fluid have?

Generally speaking, the larger the force or pressure you apply to this solution, the more it acts like a solid. Once you remove this force, it behaves like a liquid, so applying this knowledge, surely this means humans can walk on water… (mixed with cornstarch), right? Since we are so heavy, our forces acting on the surface of this Oobleck should mean that it acts as a solid upon impact, correct? Well, see below this incredible video, for yourself.

If you have any questions, leave them below and until next time, take care.

~ Mystifact


References:
[1]: https://physics.info/viscosity/
[2]: https://en.wikipedia.org/wiki/Surface_tension
[3]: https://www.sciencelearn.org.nz/resources/1502-non-newtonian-fluids

Please note; no copyright infringement is intended. All images used have been labelled for re-use on Google Images. If any artist or designer has any issues with any of the content used in this article, please don’t hesitate to contact me to correct the issue.

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