How a single particle of sand and a pile of sand behave differently!
BY IKBAL AHMED
Hey there, future scientists! Let’s dive into the fascinating world of granular materials. But before we begin, let’s declutter the jargon.
First, what are granular materials? Think about stuff like rice, lentils (dal), sand, or even tiny beads. These are all examples of granular materials. They’re just a bunch of small particles hanging out together.
Now, imagine we have this box with different compartments. Each compartment holds a collection of different materials — rice, lentils, beads, sand, you name it. But one compartment has something different — a single egg. Weird, right? So, here’s a question for you: Which one of them doesn’t belong to a particular group?
You might be thinking, “What’s the big deal about these granular thingies?” Well, let me tell you, scientists use these to explain complex physical phenomena. Even though each grain or particle in a granular material might be different in size or material, when you put a bunch of them together, something interesting happens.
A box containing different granular materials (image source: AI-generated)
When you poke them or shake them, don’t depend on what each particle is made of or how big it is.
Now, let’s relate this to our everyday lives. Think about it — these granular materials are all around us! From the sand at the beach to the rice in our kitchens, they’re everywhere. And they’re super important in industries like food, construction, and pharmaceuticals.
Okay, let’s dive a bit deeper. You know how we’ve learned about solids, liquids, and gases in school, right? Well, let’s think about what makes each of them unique. Solids, like a rock or a brick, have a fixed shape and volume. Try squeezing them into a different shape — it’s not happening! Now, liquids, like water, take the shape of whatever container you pour them into. But here’s the kicker — you can’t squish them into a smaller space. They’re what we call “incompressible.” And then there are gases, like the air we breathe. They also take the shape of their container, but here’s the cool part — you can squish them into a smaller volume.
So, here’s a brain teaser for you: Is a single grain of sand a solid, liquid, or gas? What about a bunch of them together in a granular material? Do they behave like you’d expect?
Activity 1: The Magic of Sand: Defying Gravity!
Welcome, young physicists, to an exciting challenge that will defy your expectations and maybe even gravity itself! In this mind-bending experiment, get ready to discover the secrets of sand.
Challenge: Lifting a glass full of sand without touching the glass
Materials Needed:
(1) Plastic cup filled with sand (easily available at home), (2) cardboard cylinder (you can use the inside of a paper towel or toilet paper roll)
Instructions:
1. Take your plastic cup filled with sand and the cardboard cylinder.
2. Insert the cardboard cylinder into the sand in the cup, ensuring it’s standing upright.
3. Now, here’s the tricky part — lift the cup using only the cardboard cylinder. Yes, you heard that right — without touching the cup!
Now, let’s unravel the science behind this seemingly impossible feat. You see, when you insert the cardboard cylinder into the sand, something interesting happens. The sand grains around the cylinder start sticking together, creating a sort of “sand bridge” between the cylinder and the cup.
Although it may seem fragile, this sand bridge is surprisingly strong when compressed. When you lift the cup using the cardboard cylinder, the sand bridge bears the weight of the cup, allowing you to lift it without the cup slipping off!
Real-Life Example: To better understand this concept, think about trying to lift a cup of water with a pencil inside it. It simply won’t work because water doesn’t stick to the pencil-like sand does to the cardboard cylinder.
Try It Yourself: Now, it’s your turn to try this at home! Find a plastic cup and fill it with sand. Then, grab a cardboard cylinder – you can easily find one by cutting open a paper towel or toilet paper roll. Insert the cylinder into the sand, and voila! You’re ready to lift the cup using just the cylinder.
Conclusion: This challenge shows how sand’s unique properties can defy our expectations and even enable us to perform seemingly impossible tasks. So, the next time you’re at the beach or playing in a sandpit, remember – you’re not just having fun; you’re exploring the fascinating world of physics right at your fingertips!
Activity 2: Marble Migration Challenge
Imagine you have a tube with a marble sitting at the bottom, and some sand poured on top, resembling a mini-sand dune. Your challenge? Move the marble to the top of the sand without opening the tube. Let’s delve into the physics behind this intriguing experiment.
Here’s what you’ll need:
(1) A tube with a marble placed at the bottom (like a Falcon tube), (2) a sea-sand (easily found in playgrounds or even in your backyard).
Instructions:
1. Take your tube with the marble at the bottom.
2. Pour sand into the tube until it reaches around the 40 ml mark (fill up around 3/4 of a tube).
3. Seal the top of the tube securely.
Now, think about moving the marble upwards without disturbing the tube’s contents.
What did you do to achieve this? Did your solution provide insights into whether sand behaves more like a solid or a liquid?
Here’s the scoop:
When you pour the sand into the tube, something interesting happens. The marble, being denser and heavier, naturally sinks to the bottom. However, the sand particles around it aren’t stationary; they can move. As you tilt the tube or gently shake it, the sand particles start rearranging themselves. This movement creates pathways for the marble to gradually rise through the sand, like how you might swim through a crowd at a busy marketplace.
Now, let’s talk physics!
Ever heard of the Brazil Nut effect? It’s like finding the biggest nut at the top of a mixed nut container. In our experiment, the marble represents the large Brazil nut, and the sand particles are like the smaller nuts. Despite being heavier, the marble can still rise to the top due to a phenomenon called size segregation. The larger particle gets “marooned” at the top, demonstrating this intriguing effect.
So, there you have it! With a simple tube and some sand, you can explore the fascinating world of granular physics right at home. Give it a try, and post your findings in the discussion section!