Have you ever tossed some sticks into a pond? Or maybe you like to bring a
bunch of toys into the tub!
Either way, you’ve probably found that not all objects act the same when they’re in
the water.
Some things sink right to the bottom, while other things float on the top. Why does that happen?
Well I brought in some friends to see if we can figure that out!
Hi everyone! My name’s Webb and hi
and I’m his sister, Bill! Since we live in a pond, we see a lot of things sink
and a lot of things that float!
I bet! You know, you can actually learn a lot about something by seeing what it does in the water.
So, I’d say this calls for an experiment!
[Music]
First, we’ll need a pretty big container of water. We’ll fill it about three-quarters
full, and set it up where it’s okay if some splashes out.
Now we need some stuff to put in the water.
All kinds of different stuff!
We’re gonna look for a couple things around the fort that are okay to get wet. If you want to try
this experiment at home, make sure you ask before you put anything from your house into the water!
Let’s see what we found! Alright … Squeaks found a penny, I found a stick,
and Bill and Webb, they found two different spoons, a metal one, and a plastic one.
Good job guys!
Now, before we get started, let’s take a closer look at what we’ll be testing.
All of these things are made out of different materials, like metal, plastic, and wood.
Some of them are pretty small, and some are a little bit bigger. I think we have a pretty good group
of objects, because they’re all pretty different!
Now, before we start putting things in the water, let’s guess whether each one will
sink, or float. And let’s keep track of our guesses, but, how will we… [Squeaks squeaks]
Great idea Squeaks! We’ll use a chart!
Alright, let’s start with the stick. Bill, Webb, what do you think? Will it will sink, or float?
[Ducks quacking]
Well! I, I can tell you guys are pretty excited! Tell us what you’re thinking.
Well, in the pond where we live, I’ve never seen sticks that have sunk, only ones that
float.
Well, that’s because you haven’t seen the ones that’ve sunk.
Well that's because they all float Webb.
Ok fine! Put me and Bill down for the stick floats.
Ok! Here we go. And it floats! Good job you two!
Yay! Woooo!
Next, let's try the metal spoon. What do you think? Will it sink...or float?
I’ve never seen a spoon float.
Me neither.
[Ducks quacking]
We think it’ll sink!
Ok! Let’s see.
It sinks!
Woo! We're the smartest ducks in the world! Yeah!
Now what about the plastic spoon?
Do you think it will sink, or float?
[Ducks quacking]
Well, it’s the same shape as the other spoon.
Yeah!
And, we think it might sink, just like the metal spoon did.
Okay, let’s see.
It floats!
Awww bummer!
Well, that’s okay, guys, that’s how we learn, right?
Yeah, I guess. It’s just weird! The other spoon sank!
Well, let’s record our results and see if we can find out why it sank after we test our next
object.
Our next object, will be the penny. Do you think it will sink...or float?
Hmmmm... well, a penny feels a lot like a metal spoon. So... I think it’ll sink.
Alright, and Webb what do you think?
Well it’s so light, but kind of small, and I don’t usually see things that small
floating...uhh... I'll have to agree with my sister this time. It’s gonna sink.
It sinks! Good Job! [Celebrating]
Woo-hoo!
Now that we’ve tested all of our objects, let’s look at our chart. Some of the objects
floated, and some of them sank.
Let’s see…
...the metal spoon and the penny sank… ...the plastic spoon, and the stick floated.
Is there anything that’s the same about the things that floated and the things that sank?
Well, we know that the metal things sank. And the metal spoon feels kind of heavy…
...but so does the stick...and the stick floated, while the spoon sank. So maybe it’s not
all about how much something weighs or it’s shape?
You're right! And that might help us explain why some things float and some things sink. The answer
has to do with something called density.
Everything, and I mean EVERYTHING, is made of tiny particles that we can’t see. And
how dense an object is depends on how much space is between those particles.
Particles?
Jessi, what the quack is a particle?
Now, that’s an awesome question! Let’s use our imaginations and pretend that particles
are marbles. We’ll start with a bunch of marbles on a table. If you had the marbles
all right next to each other, that’s kind of how the particles would look inside an
object that's dense … like the metal spoon.
But if those marbles were spaced really far apart, that’d be more like what the particles
are like in something that’s less dense … like the plastic spoon.
The metal spoon is more dense than the plastic spoon. It’s about the same size and shape,
but the particles that make it up are closer together than the particles that make up the
plastic one.
But remember! Everything has density...including water!
Whhhaaatt?
It’s true! Since water has it’s own density, if something is more dense than the water
it’s in, it’ll sink.
The metal spoon and the penny were more dense than the water, so they sank…
and the stick and the plastic spoon were less dense than the water...so they floated.
So, will it sink, or will it float? It depends, in part, on density!
How did your experiment go?
Did you make some wrong guesses like us?
I bet you got some right!
Let us know what you use in your experiment, and how it turns out! Just get help from
a grown up and leave us a note in the comments below, or send us a picture at kids@thescishow.com!
And we'll see you next time! Bye!