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As you watch the video, consider these questions:
• What effect does heat have on metals?
• How are metal structures like bridges and buildings designed to survive the effects of heating and cooling?
Child: The surfing scientist is the best.
Ruben Meerman: Uh, oh.
Child: The surfing scientist is awesome.
Child: Surfing science is like amazing.
Ruben Meerman: Let's do an experiment with something which is made of something solid. So, this is a solid piece of metal it's aluminium actually.
Ruben Meerman: Same stuff you use to make soft drink cans. And this thing here is a solid metal ball that just fits through the hole in the metal ring, but it only just fits through there right
Ruben Meerman: So you might recognise that. Used to be the tow ball on the back of my car. Have you ever seen those on the back of a car?
Children: No. I have.
Ruben Meerman: Well the ball only just fits through the hole in the metal ring but have a think about this. If that metal ring was smaller would that ball still fit through there?
Ruben Meerman: No, and if the metal ring was bigger would the ball fit through? Yes. Alright well let's put it into the liquid nitrogen and see if anything happens. In it goes. I better put my gloves back on now.
Ruben Meerman: And we'll see if it changes the same way the balloon changes. It went from that big to that tiny didn't it? So let's see if anything's changing.
Ruben Meerman: It looks the same doesn't it? Maybe it needs longer. We'll put it back in there for a little while. Mm, that's not very exciting. Let's have another look at it. Still the same.
Ruben Meerman: Let's put it back in for a little longer. Mm, well alright I don't know what else to do here. We'll have another look and if it doesn't the same, any different.
Ruben Meerman: But let's see if the ball still fits through there. There we go, one, two, three. Hey it doesn't fit through anymore. So is it bigger or smaller?
Ruben Meerman: Smaller and all we did to it was make it freezing cold. Now if it gets smaller when you make it cold what do you think we'd need to do to it to make it bigger?
Children: Warm it up
Ruben Meerman: Warm it up. Well let me show you how cool this looks. If we put it back in there for just a second, take this big container of water and stick it on top of there so you can see.
We'll get the ring nice and cold again and you can see the ball doesn't fit through. But the water here is much, much warmer than my liquid nitrogen so let's put it in there and it should get bigger
and eventually it should fall through the hole again. Here we go.
Hey, it got bigger. And all we're doing to it is making it colder or warmer. Now that's pretty amazing. It's another change that you can't really see with your eyes because it's too small a change to see
But the ball can notice it.
So, now you know that even solid things even though they don't get heaps bigger and heaps smaller they only change by a little bit but even solid things get a little bit bigger if you heat them up and a little bit cooler, uh smaller if you cool them down.
And here's something that I find absolutely amazing about that Sydney harbour bridge, you know the big bridge just down the road. The Sydney harbour bridge is made out of metal right same as this.
This is a type of metal Sydney harbour bridge is made out of steel. And when the sun shines on it, the Sydney harbour bridge gets really, really hot. Have you ever walked across the bridge?
Ruben Meerman: If you're walking across the bridge one time on a hot, sunny day and you touch the metal and you go, ow. It feels like it will almost burn you
Ruben Meerman: It's so hot in the sun. But at night time it cools right down and gets really cold. And you've just seen what happens to metals when you heat them up and cool them down.
Ruben Meerman: So, even the Sydney harbour bridge gets a little bit bigger and a little bit smaller during the day.
Ruben Meerman: But because it's so big already the Sydney harbour bridge is forty nine centimetre, that's this long, forty nine centimetres longer during the day than it is a night time. That's amazing
Ruben Meerman: And to make sure that it doesn't sort of bend and buckle and fall apart, when they built the Sydney harbour bridge, they built it on great big hinges.
Ruben Meerman: The same as what you use to make a door swing except the hinges on a door allow a door to swing that way,
Ruben Meerman: whereas the big hinges that the Sydney harbour bridge is built on swing that way so that as it heats up during the day, it can expand a little bit during the day and shrink a little bit a night time.
Ruben Meerman: It's amazing isn't it? So next time you go under the bridge, have a look up and you'll see the great big hinges that it's built on.
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Watch as Ruben puts a squash ball into liquid nitrogen. Think about these questions:
• What are the properties of an elastic material?
• What happens when an elastic material is cooled down?
• How are elastic materials useful to humans?
Ruben Meerman: Let's have a look and see what else we've got. Oh yes. Let's do an experiment with this thing which is a little rubber squash ball.
It's made out of rubber the same as your bicycle tyres are made out of rubber. And it's a hollow little ball and you can squash it.
You use it for a game called squash right. Now this little squash ball at the moment is nice and warm and is a very good example of an elastic material.
Elastic means you can either squash it or stretch it and it doesn't break and it always comes back to the shape it started. So that's a good example of an elastic material right.
Now we're going to put this in liquid nitrogen and see if it's still elastic.
Ruben Meerman: Yes. Have a listen to the sound this squash ball makes when it hits the table when it's warm. Remember this sound.
It's not the most exciting thing. But I want you to remember that sound because it might change.
Because now it's going to go into liquid nitrogen. What's it like in there I wonder?
Pretty chilly. Let's grab it out and there it is. Looks the same. Have a listen to it now.
Ruben: Woah, yes. It sounds rock hard doesn't it? Does that still sound like it's an elastic squash ball to you?
Ruben Meerman: No it doesn't to me either and I can't really squash it with the tongs. So I'll put it back in there for a second.
We'll do a little experiment to see if it's still elastic.
I can't squash it with the tongs very easily but maybe I can squash it with the help of my good friend here, mister hammer.
Ruben Meerman: And now let's have a look here. What I might do though is I'm going to wrap the squash ball up with a tea towel first
so that I don't want bits of squash ball to go flying everywhere so I'll put the squash ball on the tea towel and then we'll wrap it up, oh hang on.
And then there it is can you see it there? And then we'll give it a nice little gentle tap. One, two, three.
Uh oh. That didn't sound good did it? Let's have a little look and oh no. It's smashed into little pieces.
It's like Humpty Dumpty. Well does that squash ball look elastic to you?
Ruben Meerman: No. Elastic materials are things you can squash and they don't break and when you stop squashing them they come back to their original shape.
That piece of squash ball is completely hard, brittle. So it's lost all its ability to be bent or squished, it's not elastic but at the moment it's very cold.
By the way you can touch this with your bare fingers because it's made out of rubber and rubber doesn't conduct heat very well.
But if it was made out of metal you couldn't touch it with your bare fingers 'cos metal does conduct heat very well.
So, bit because it's rubber you can rub it with your fingers and as you do it starts to heat up again.
Now if you try to bend those pieces they break because they're still cold. But this piece, now that it's warm again, have a look at this, you can squash it again.
That's pretty amazing so this elastic material gets less elastic if you cool it down and it gets more elastic if you heat it up. That's a pretty incredible thing and a completely reversible change
So there are some things that aren't reversible like for instance if you change a piece of wood by putting it in a fire, you can't unburn a piece of wood so that's not a reversible change.
This change here well if I hadn't hit the squash ball with a hammer, this squash ball would be a okay, back to normal, nice and elastic again completely reversible change.
Ruben Meerman: But I accidentally hit it with a hammer so I can't really do that. I'll leave that with your teacher so you can have a look at it.
You might even want to try and put it back together but I don't think you're going to have much luck. So I reckon we might put that one away.
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As you watch the video, think about:
• what happens when liquid nitrogen evaporates
• why the balloon blows up
• the importance of personal protection when using dangerous materials.
Ruben Meerman: undefined
Ruben Meerman: Ruben Meerman Cool, well let's do another experiment. This time I want to show you why this lid is such a weird looking thing. Did you notice that lid before?
Ruben Meerman: It's a pretty unusual looking lid isn't it? It's not the sort of lid you'd put on a soft drink bottle like a screw top lid.
Ruben Meerman: It's kind of got this corky thing but normally a cork in a bottle you make them really tight so that the cork seals the bottle. But does that look loose or tight to you?
Ruben Meerman: Yes, really loose. So that seems strange because that means that if you knock this bottle over that loose lid will just pop off and liquid nitrogen will go all over the floor.
Ruben Meerman: That sound weird doesn't it? Why wouldn't you just put a nice tight lid on it?
Ruben Meerman: Well I've got an experiment to show you why you can't put liquid nitrogen in a bottle that has a tight lid. So here's a container that used to have chocolate in it, right.
Ruben Meerman: And it's got a tight fitting lid that snaps on nice and tight. And we're going to put a little bit of liquid nitrogen in here, put the tight fitting lid on and we'll see if there's a good reason for that one being loose.
Ruben Meerman: So let's pour a little bit in and here we go. Tight lid, loose lid. Let's see what happens. One. Two, three.
Children: Laughter, do it again
Ruben Meerman: Woah, sorry did you get a fright? Yes, me too. Shall we do it again?
Ruben Meerman: Alright here we go, one, two, three.
Ruben Meerman: Oh it's not working this time. Did I push it down enough? Oh no there's a little bit of a seal there.
Ruben Meerman: Oh, crikey. Gives you a fright doesn't it?
Ruben Meerman: Luckily it's just a little plastic lid 'cos if that was a really piece of metal type lid can you imagine how dangerous this lid would be?
Ruben Meerman: We're going to do it one more time and then we are going to find out why this lid keeps coming off. So, one last go. One, two, three.
Ruben Meerman: Got me again. Oh crikey, Well let's find out why this lid keeps popping off.
Ruben Meerman: First of all you can see that having a loose lid on this bottle is a really good idea, not a silly idea because if that was tight then every five seconds it would go kaboom and shoot off there
Ruben Meerman: And if someone happened to be standing here like this and it went kaboom and it would go boom, ow. So that'd be dangerous wouldn't it?
Ruben Meerman: Well the reason this lid keeps popping off is because we've got a liquid here that's freezing cold. It's minus one hundred and ninety six degrees Celsius.
Ruben Meerman: But planet earth is much, much hotter than this liquid. So it does what water does if you heat it up. Have you ever noticed what puddles do on a hot day?
Ruben Meerman: If it rains you get puddles but they don't last forever do they? They dry up. Do you know what the name for that is when puddles dry up? Yes?
Ruben Meerman: You know when it's the opposite of condensation. Do you know what the word is?
Ruben Meerman: Oh very close. That's water can dissolve stuff. When a puddle dries up and turns into invisible gas, it's called yes …
Ruben Meerman: Very good, it's called evaporation. Well, liquid nitrogen evaporates and turns into an invisible gas.
Ruben Meerman: That invisible gas starts off very cold but planet earth's very hot, so the gas is going to heat up and heat up and what do gases do when they heat up?
Ruben Meerman: Do you remember Pepe the poodle? When he was cold he was small and when you heat him up he gets …
Ruben and children: Bigger
Ruben Meerman: Well let's see what happens when we pour some liquid nitrogen into this container. We'll put this tight fitting lid on.
Ruben Meerman: As soon as it gets its lid on the liquid nitrogen is evaporating down the bottom and turning into gas will get trapped in the bottle as it heats up even more it'll get bigger which will fill up the balloon which will get bigger and bigger until it goes, bang.
Ruben Meerman: Right, now. Should be a bit of fun and a little bit noisy. So I'm going to make some ear plugs for this experiment.
Ruben Meerman: You can use your hands to cover your ears. I can't because I need them so I'm making ear plugs out of paper towel.
Ruben Meerman: They probably won't look very professional, in fact, no they don't look very good do they?
Ruben Meerman: Well there's one ear plug. There's another.
Ruben Meerman: Right, here we go. They'll remind to cover your ears if you don't like loud bangs.
Ruben Meerman: So, in goes the liquid nitrogen and on goes the lid. And we're away. One, two, three, ooh. Uh, oh.
Child: This is going to be so cool.
Ruben Meerman: I might move that. Oh, my goodness.
Ruben Meerman: It's huge. Uh, oh. Is it going to blow? Come on.
Children: Squeals and laughter
Ruben Meerman: Crikey, wow. Hey look at that. Hey.
Ruben Meerman: We can put that back on there and.
Ruben Meerman: Hey that's a bit of fun.
Ruben Meerman: Well, pretty fun isn't it? Oh, there's bits of balloon everywhere. Oh look there's balloon all the way over here.
Ruben Meerman: Can I show everyone this? Look what's happened to the balloon.
Ruben Meerman: It's like streamers. It got absolutely shredded into little pieces. That's amazing. Well, that was the last experiment I've got time for this morning but ooh.
Ruben Meerman: But has anyone got any questions about any of those experiments? Or, you got a question?
Child: Could that liquid freeze lava?
Ruben Meerman: That's a good question, would this stuff freeze lava? It certainly would do a very good job of cooling it down very quickly.
Ruben Meerman: It's not used to fight fires because water is also very good at cooling down a fire and water isn't as dangerous as this, so they don't need to fill up fire trucks with this to fight fires because water does just as good a job.
Ruben Meerman: But if you pour this onto molten lava it would cool it down very, very quickly.
Child: How does it stay cold?
Ruben Meerman: Ah, good question. It stays cold in this container because this is like a big thermos flask just like the ones you have at your house to keep tea and coffee in.
Ruben Meerman: But it won't last in here forever. If I fill this container up full, it's ten litres worth.
Ruben Meerman: But if I didn't touch it and left the lid on in five weeks time it will still be completely empty because it evaporates away so it won't last forever.
Ruben Meerman: It'll slowly evaporate and turn back into gas. Is that an alright answer? Sort of.
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As you watch the video, think about these questions:
• What sort of discoveries can be made through experiments?
• Do investigations always lead to expected outcomes?
Ruben Meerman: Let's just finish off with that explosion again. This time. Good idea? Yes.
Alright. Oh, ho, deary me. Well we'll tie this up, and then we'll blow it up very quickly. It's a bit different to when you use a round balloon.
Still very loud so cover your ears but it's a different kind of loud. It's a higher pitched bang and it'll be pretty quick. So I'm going to need.
Oh jeez I got rid of my ear plugs. Needs some new ear plugs. And put one in there and the other one in the other ear.
Silly aren't they, I know. Goggles back on, gloves. And in with the liquid nitrogen. There you go. Uh oh, righto. Everybody ready? Here we go, one, two, three.
Oh my goodness gracious me. Look at it go. Now we'll finish off with have a look at this.
We'll finish off with a nice big cloud. We'll turn this container upside down and
Amazing. It's cool isn't it? Well there we go. That's the end of the experiments. I hope you've had a lot of fun.
Ruben and children: One. two.
Child: The surfing scientist is cool and amazing.
Ruben Meerman: Hello Pepe
Child: The surfing scientist, he's the best.
Ruben Meerman: See ya.
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