Experiment: The Brazil Nut Effect

In Stratification & Segregation: Why Does Some Sandstone Have Stripes? [1] Hernán Makse shows how sand grains of different sizes and shapes may naturally separate after being thoroughly mixed together. Here's a way to show how large grains separate from smaller grains.

Tools & Materials

A glass jar about a liter (a quart) in size, with a wide mouth
Uncooked rice to fill the jar about three fourths of the way to the top
A small rubber ball

The Experiment

Put the ball in the jar along with the rice. Push the ball down so that it is buried in the rice.
Now place the jar on the table and shake it back and forth. What happens? Can you explain the phenomenon?

But why is it called the "Brazil Nut Effect"? When you open a can of mixed nuts -- peanuts, cashews, almonds and Brazil nuts -- it often seems that the big Brazil nuts are on top. How did it happen?

Check our results. [2]

Course:

Science [3]

Result/Solution(s)

We took the jar with the rubber ball buried in the rice and shook it back and forth for a few minutes.

The ball popped up out of the rice!

Can of nuts When we opened our can of Mixed Nuts there were four Brazil nuts visible on the surface. We closed the can and shook it back and forth for a few minutes as we did with the jar that had the rubber ball buried in rice.

When we opened the can there were five Brazil nuts visible on the surface.

As we ate the nuts we found a total of ten Brazil nuts in the can. When we got toward the bottom we found mostly peanuts.

The Brazil nuts are considerably larger than any of the other nuts in the mix. Like the rubber ball in the jar of rice they tend to rise to the surface when the container is shaken.

The can of mixed nuts contained
Brazil nuts, cashews, almonds,
filberts, and peanuts.

There was most likely a whole lot of shaking going on while the nuts were being transported by truck or train from the factory where they were canned to the store where they were sold. That's probably why there were already four of them on top even before we shook the can.

earth science [4]

ps_nid:

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