Inside: Use LEGO and sand to study physics with kids. Grab a bucket of sand and some LEGO bricks for a quick demonstration of a Brazil Nut Effect.
Have you noticed that beach trips aren’t what they used to be when you were a child?
When I was a kid, a beach trip was all about splashing in the waves, chasing seagulls, and looking for seashells and stones.
Now I’m a mom.
Every beach trip starts with military precision packing. From sunscreen to drinking water, the list goes from here to China and back again.
The actual time at the beach involves keeping a vigilant watch on my older kids, while chasing my energetic toddler.
It all ends with a few hours of de-sanding my home—removing five pounds of sand that somehow mysteriously traveled from the beach with us.
Exhausting? Yes. Boring? Not necessarily.
I try to make beach time more fun for myself with edu-fun-cation: education + fun + vacation. That’s the term I came up with for turning any outing with our kids into a science adventure.
Yes, I do have to do more preparation in advance, but once we are at the beach and I need a break from “the usual,” I put my toddler in a carrier, call my kids over, and we do some science together.
Let me share with you how you can observe the Brazilian Nut Effect with LEGO pieces and sand.
Brazil Nut Effect with LEGO and Sand
Have you ever looked at a bowl of mixed nuts and wondered why all the large nuts are on top? I like hazelnuts, so I’m forever digging around trying to find them at the bottom. It’s inconvenient, but it’s also counterintuitive. Shouldn’t all the big, heavy pieces end up on the bottom? (What are your favorite nuts?)
So finally I googled “why Brazil nuts are always on top.”
You could have knocked me over with a feather when the results came in.
It turns out it’s a scientific phenomenon that scientists (physicists to be exact) study in the lab. And it has a fitting name. Did you guess it? The Brazil Nut Effect.
The Brazil Nut Effect (its official name is granular convection) refers to size-separation of granular material in response to jostling and stirring. It simply means that when you have a mixture of different sized objects, larger objects end up on top.
I thought, “Wait a minute. Does it mean, if you throw a bunch of LEGO pieces in a bucket of sand they will all pop up?”
I had to try!
What you need
NOTE: We choose to do our experiment on the beach, but you can do it anywhere there is sand.
What to do
Fill your bucket halfway with sand and add the LEGO pieces.
Cover the LEGO pieces with sand.
Ask your kids what they think is going to happen to LEGO pieces once you start shaking the bucket.
Shake the bucket. The goal is to create a vertical vibration. Watch our video below.
See the LEGO pieces popping up out of the sand?
We were so surprised that a simple shaking motion could uncover all of our LEGO pieces that we kept doing it again and again with LEGO bricks of different sizes and shapes and with DUPLO blocks. And in different buckets.
Note: Why fill the bucket halfway with sand before adding LEGO pieces? To speed up the results. You can put the LEGO pieces at the bottom of the bucket and fill it all the way to the top with sand. It works! It just takes longer for the pieces to work their way back up. If your kids have a shorter attention span, you might find them wandering off before they can see the magic (I mean the end of the experiment).
Some kids might enjoy hiding the LEGO pieces in the bucket’s sand one by one. My 3-year old certainly is a big fan of filling the bucket with sand and then pushing each LEGO piece in manually.
Related: Books to get your kids swimming
What is happening
As you shake the bucket, the particles from the center of the container are pushed upward, leaving small empty spaces that are immediately filled with small particles sliding down. But unless a big gap opens up among the small particles, the bigger pieces can’t go back down. They stay on top.
There is a little nuance to the Brazil Nut Effect that you might or might not want to mention, depending on the age of your children. If there is no substantial difference between the density of bigger particles and small ones in your mix, the objects will stay mixed. You can experiment with it at your leisure.
If you are a kid, time at the beach is all about discovering and exploring. But if you are a mom who wants to make beach time more fun for you, you can add this simple science activity, and nobody would even guess that it counts as physics for the day.
If you like playing and learning with LEGO, check out some other LEGO posts.