Question

1. Skip to 2:51 in the video below. The host uses a small magnet to attract a piece of (totally not a Cheerio for copyright reasons) cereal floating in water. We know that cereal as a whole is not magnetic (it's not going to stick to your refrigerator or collect towards the North side of the cereal bowl), so what could be causing this? Make a guess, and explain the physical reasoning behind it?

https://www.youtube.com/watch?v=1Xp_imnO6WE

2. Begin watching the host's explanation, which is the first in the video below. Pause at 1:08. Upon grinding up the cereal, what is his first explanation for the attraction between cereal and a magnet? What evidence does he offer that this explanation is actually insufficient?

3. Watch the rest of his explanation. What is actually causing the apparent "attraction" between the magnet and the non-magnetic object?

https://www.youtube.com/watch?v=jIMihpDmBpY

Answer 1

1. Cereal has a lot of iron content in them, that means the metal iron is present as a composition of it. As magnet attracts iron the cereal is attracted towards the magnet too.

2. The host indeed points out that a part of the grinded cereal is attracted to the magnet because it contains iron, the printed composition on the box directly mentions it too.
But upon further investigation many non magnetic material like paper and plastic floating on the surface of water also gets attracted to the magnet and they do not contain any iron. So the explanation is insufficient.

3. Water is diamagnetic, i.e. it slightly repels the magnet and create a local minute depression on the surface of water, the floating objects generrally fall towards this depression and this seems like an apparant attraction.