The Cheerios Effect
At the breakfast table have you ever noticed that your cereal floats or sticks together on the edges of your bowl and wondered why? Now most of you would have not bothered to find the answer. Well, nobody knew the exact answer to this, but some scientists thought that they should find a reason for this. And eventually, they did which is called ‘The Cheerios Effect’. They made a discovery which not only answered the above question but also how do other objects like coins and paperclips or even insects float on water. If this has made you curious you may want to keep reading further.
Well let’s start by knowing what is cheerios effect?
“The Cheerios effect arises from the interaction of gravity and surface tension; the tendency of molecules on the surface of a liquid to stick together, forming a thin film across the surface.” Research published in Physical Review Letters
How does it work?
Well the weight of the cereal is less than that of the milk and so is able to float on the milk. If we look closely there’s an upward curve where the cereal meets milk, even on the edges. This is due to the Meniscus effect. Water molecules are very sticky. They are attracted to each other but even more attracted to the edges of the container and the object. They make the objects stick together and push the object to highest meniscus point. This also leads to the formation of a U shape. So when the cereal is poured into the bowl it moves towards the edges and forms an upward curve.
In fact, the water molecules hold on to each other so tightly that they form some kind a layer, that can hold light weight objects on the surface. For example, leaves, insects or even properly placed paperclips, pins and coins.
Can we stop the Cheerios effect?
Yes. This can be changed by adding just an appropriate amount of soap. This is because the chemical properties of soaps interfere with surface tension of the water by lowering it. Which then makes anything that can float on the surface of water, sink. However, this does not apply to cereals or other buoyant objects as they do not rely on the surface tension.
Therefore, as Mahadevan explains the Cheerio Effect using three basic concepts from physics: buoyancy, surface tension and the meniscus effect.