Water play

(Children) Boats.

(BJ) Hi, I’m BJ.

Welcome to Science Time, Experimenting at Home.

Do you like experimenting?

I do and at home we can do lots of different science experiments.

Today we’re experimenting with boats.

Do you like boats?

Have you ever seen a boat on the water?

Have you ever been in a boat when it’s on the water?

They’re lots of fun aren’t they?

Here I’ve got a rock.

So, we’re going to do some experimenting with water.

What do you think will happen to this rock when I put it in the water?

Let’s do an experiment and find out.

When you do an experiment in science you start by asking question,

having a bit of a think about what you think might happen,

and then you can do a test to find out.

So, what will happen when we put the rock in the water?

Have you had a think?

Shall we test?

Oop, it sank to the bottom.

Float or Sink

Is that what you thought was going to happen?

Yeah.

Lots of things when you put them in water they’ll either float or sink.

You can do some floating and sinking experimenting at home.

You can get a tank of water like this one or you can use anything that holds water, little containers, or the bath is a great place for doing floating and sinking experiments.

So, I’ve got a question, why does this little rock sink to the bottom of the water when a big, heavy boat will float on top of the water?

How does that happen?

Let’s do some more experimenting and find out.

So, here I’ve got a container with water.

And do you notice I’ve put some blue tape here at the top of the water and that marks where the level of water is.

Now, what happens to water when we put something in it?

Let’s test and find out.

So, here I’ve got a whole bunch of rocks.

Let’s put some rocks in the water and see what happens to the water.

So one, can you count with me? Let’s count together.

Ready, one, two, three, four… what’s happening to the water… five, six.

Can you see what’s happening to the level of water?

Is it still on the blue line?

It’s gone above the line hasn’t it.

So, the water level has risen.

When I put the rocks in the water they need to make room for themselves so the rocks push the water out of the way and it displaces that water.

The water’s got to go somewhere so it comes up and it makes the water level rise.

You can experiment with this at home in the bathtub.

Next time you have a bath ask your grown up to mark the level of water

with some tape like this or a little waterproof pen and then get into the bath and see what happens to the water level.

I wonder what will happen.

You can experiment at home and find out.

So, how does pushing water out of the way

make things float like big, heavy boats?

Let’s do some more experimenting.

So, here I’ve got two balls, a ping-pong ball and a golf ball.

Have you ever seen ping-pong ball and golf ball?

They’re the same size.

They’re the same shape but there’s something that’s different about them,

the weight.

The ping-pong ball just has air inside so it’s very light

whereas the golf ball has rubber inside and that makes it quite heavy.

So, one is heavy and one is light.

Do you think that will make a difference

when I put them in the water?

Let’s experiment.

I’ll get the rock out.

What do you think is going to happen

when we put our golf ball and our ping-pong ball in the water?

Let’s test and find out.

Weight

Oop, what happened?

The ping-pong ball floated on top

but the golf ball sank to the bottom of the water.

They’re both pushing water out of the way

and water also weighs a bit as well.

If something is lighter than the amount of water it pushes out of the way like our ping-pong ball it will float on top of the water.

But if it’s heavier than the amount of water it pushes away,

like our golf ball, it will sink to the bottom.

So weight has a bit to do with why big boats float.

But boats can be pretty heavy can’t they?

So, it can’t just be the weight.

Let’s do more experimenting.

I’ll get these balls out of the water.

Now, I’ve got a container lid.

You’ll probably have one of these at home in your kitchen.

I’ve put a black cross on it so we can see it well on the video.

So, what will happen when we put this lid in the water.

What do you think?

Let’s test and find out.

Oop, it floats, it floats on top of the water.

Float

OK well let’s put our lid in a different way.

We’ll put it this way.

What do you think will happen?

Let’s experiment and find out.

Did you see that?

Hey, we’ll do it again, watch.

It sank.

So, why did the lid float one way and sink the other way?

Mm, when we put it this way

only this little edge here is pushing water out of the way

so it doesn’t push much water

and the lid is heavier than the little amount of water that it pushed away.

But if we hold it like this with a big, flat surface here,

it’s pushing more water out of the way

and now it’s lighter than the amount of water it’s pushed out of the way and it will float.

So, boats need to push a lot of water out of the way

when they are on the water in order to float.

Now, lots of boats have big bits like this

under the water that push lots of water out of the way

and makes the boat float.

Now, you can make a boat out of all different sorts of materials at home.

You can do your floating and sinking experiments

and maybe make a boat out of something that floats.

So here, I’ve got a stick.

What will happen when I put the stick in the water?

What do you think?

Do you think it will float or sink?

Let’s test and find out.

Boats

It floats.

So, sticks are really good things to make boats out of.

Here I’ve collected a bunch of sticks from the garden

and I wonder if my little stick boat will float.

You can make a stick boat at home and find out.

Now, other materials we could use

is foil.

You might have some foil in your cupboard at home.

Now, both these pieces are exactly the same size.

So, they’re the same weight

and made out of the same materials

but I’m going to make two different boat designs.

This one I’m going to fold up like this and make a nice flat raft.

But this one I’ll fold up, and instead of being flat,

this one I’m going to make with sides.

Have the boats that you’ve seen,

have they been flat, or have they had sides?

Mm, so this one has sides.

So, do you see what I’ve done there?

You can get your grown-up to help you with this.

I’ve folded up the edges and now it has sides.

So, we’ve got our flat raft and our boat with sides.

What do you think will happen when we put them in the water?

Shall we test?

Oop, look they both float really well.

Now, at home a great experiment you can do

is try to build a boat that will carry the most weight.

So, I’ve got some rocks here.

We’ll get our rocks from before

and let’s see how much weight our raft

and our boat with sides will hold.

So, we’ll do one rock on each.

OK, ready.

Oh, they’re both floating.

Shall we try a second rock?

Here we go.

Oh, our boat with sides is floating.

Oh no, what happened to our raft?

It sank.

But our other boat is still floating really well.

I wonder how many more rocks we can put in it before it sinks.

Shall we keep going?

So, we’ve got two, three, oh, three rocks it held.

So, at home you can experiment with

boats made of foil just like this,

or you can use other things as well.

Containers like a milk bottle are really good,

and you can put it in the water and see

how many of your toys you can put in your boat before it sinks.

Another fun thing to do with boats is to make them move.

So, I’ve got my little container boat here

and how could I make the boat move?

I could push it;

there it goes to the other side.

Is there any other way we could make our boat move?

Maybe we could put something on the boat, something like a sail.

Have you ever seen a sail boat with big sails

that catch the wind and make the boat move?

You can make a sail out of all different sorts of things.

So, here I’ve made a sail out of paper

and I’ve also made a sail out of a leaf.

You could use all different things

and you just need something to put your sail on like a mast it’s called.

Here I’ve used a stick or a wooden stick here.

You could even use a pencil, anything that’s straight.

And you could put it on your boat and then you can be the wind

and you can attach your sail to your boat and do a big blow

and see how far you can move your boat.

And you can experiment with what you make the sail out of,

also the different shapes of sail.

You could use a square one, a rectangle one, even a triangle sail,

and see how that changes the way your boat moves.

There’s so much experimenting you can do with boats at home.

And I want to see your experiments.

So, you can take a video like I have today, or take a photo.

Send them to us on our email or post them online.

There’s so much fun you can do experimenting at home.

So, I’m going to put my sail on my boat and see how far I can make it move.

You have fun experimenting at home and I’ll see you next Science Time.

Bye.

[Song] There is science outside, at the playground, in the sunshine.

There is science. Wake up.