Why Won't it Mix? Discover the Brazil Nut Effect

Introduction

Have you ever noticed that the dried fruits or nuts in your breakfast cereal are not evenly spread out inside the box, or that in a container of mixed nuts Brazil nuts gather at the top? This phenomenon is commonly called the "Brazil nut effect," and the science behind it is surprisingly complex and far-reaching. This phenomenon can be a nuisance when you want to fill silos, bags, or bins with different types of materials. It can also be used to our advantage: an avalanche airbag uses the Brazil nut effect to keep skiers on top of the snow during an avalanche! In this activity, you challenge yourself to mix different kinds of granular materials. It's not as easy as it sounds!

Credits

Materials

• Empty, transparent cylindrical container. Electrical tape containers, makeup containers, or Petri dishes are good options. A small food container works too.
• Colored sand (available at arts and crafts stores), enough to fill your container 1/3 full. Sifted dry sand from a sandbox or extra fine granular sugar is fine, too.
• Single color of dessert sprinkles. Make sure your sand and sprinkles are each a different color so when mixed, you can easily tell them apart.
• Measuring spoon
• Small spoon or spatula
• Additional granular materials such as lentils, flour, rice, ground coffee or coffee beans, dried fruit, etcetera