AMASE: Bubbles

[Woman and child sitting at kitchen bar looking at camera blowing bubbles with bubble gum]

[Bubble popping sound]

Joanne: Today on Ask Me Anything: Science Edition we're talking about... 

Mara: BUBBLES! So, mom why do when you blow bubbles they pop? 

Joanne: Ah good question. So, it's all about forces. So, there's air inside that's pushing out and there's air outside that's pushing in and in the material there's a stretchiness that's called surface tension.  

[Video cut to child outside making bubbles with a wand]

Joanne: So, if there's more pressure pushing outwards, and you get a little bit of a tear then the surface tension in the material rips the whole thing 
apart and it pops! 

Mara: Ah that makes sense. Like this!

[Video cut back to the kitchen. Joanne blows a bubble until it pops.]

Mara: There we go!

Joanne: You want to try this out in more detail with a balloon? 

[Mara gets a balloon from the counter in front of her.]

Mara: Yeah. 

Joanne: All right. So, what do you think will happen if we take this skewer and we touch it to the side of the balloon.  

[Joanne takes a skewer from a container on the counter.]

Mara: It'll probably pop. 

Joanne: Okay it'll probably pop, but did you know that there's actually a way to put this skewer through the balloon without it popping? 

Mara: Really? 

Joanne: Do you want to try it? 

Mara: Yeah!  

Joanne: Okay, so right by the knot where you see that it's kind of stretchy and the knot is darker there's not as much surface tension. So put it through there. 

[Mara takes skewer and locates the spot on the balloon.]

Mara: All right.

Joanne: Okay, push... push... okay, all the way through. 

Now if you look on the other side opposite the knot there's a little bit of a bump where it's darker than the surrounding material so see if you can get it lined up to come out through there. 

[Joanne lining up skewer on the other side of the balloon.]

Okay so push it through... push it through until you... oh! There we go! Okay! So, see, we can put it right on the bump so we push it through and TA-DA! We have our skewer through the balloon and it hasn't popped.  

Mara: Although it's kind of losing air. 

Joanne: So, we can pull it all the way through and the balloon is still fine! 

[Joanne pulls the skewer all the way through.]

Mara: Except it’s kind of losing air. 

Joanne: Well, a little bit because there's now a tiny hole but there's nothing magic about this balloon... we do this! 

[Joanne uses skewer to pop the balloon.]

Mara: It's like magic. Okay no it's not magic 

Joanne: it does the exact same thing you predicted where at the side there's more surface tension so as soon as you make a little hole the surface tension rips the whole bubble apart. 

Mara: Fun!

Joanne: Totally.  

And did you know that bubbles and balloons are fun but they're also useful? 

Mara: Really? 

Joanne: Yeah! Remember that video we were watching about the emperor penguins trying to get out of the water quickly?  

[Video cut to penguins swimming.]

Mara: Oh! Where they like fluffed up their feathers with a bunch of air and then they dove down and then they created a bubble of tunnels... a tunnel of bubbles... to come out there? 

Joanne: Yeah! They come shooting up through this tunnel of bubbles and 
what that does is it makes it much easier for them to swim through the water so they can get out of the water up to like three times faster than if they just came swimming through the water which is pretty useful if there's say a hungry sea lion in the water! 

Mara: Yes. Very useful. 

Joanne: So, there's a demonstration that you can do at home to look at the same kind of thing. Not exactly the same but similar. The effect of bubbles on materials in different liquids. So, we've got some fizzy water here that we're going to put into a container and then we've got some raisins. So, what do you think is going to happen if we drop the raisins in the container? 

Mara: They'll sink. 

Joanne: All right let's see what happens. Drop the raisins in. 

Mara: All of them? 

Joanne: Not all of them, just like a handful. All right. That's what happens! 

Mara: Wait! Whoa! Like the bubbles like picking up the raisins and then when they get to the top the raisins are like the bubbles are coming off and then the raisins sink again. 

Joanne: Yeah, this is what we call dancing raisins. What's happening exactly is that the raisins are kind of rough so it's a nice spot for the bubbles to accumulate. That's what we call nucleation. 

So, the bubbles accumulate on the raisins and when enough bubbles accumulate they lift the raisin to the top. The bubbles evaporate away and then the raisin sinks back down again. So, you can try this at home. All you need is some raisins and either some fizzy water or some pop, whatever you like, and you can make those raisins DANCE!

[Mara dances in her chair.]

Mara: OH! Is this like the thing with mentos and diet coke where like the mentos are rough so when you put it in the diet coke there's like a million bubbles and then it spews out the top?  

Joanne: Absolutely! So, it's the same thing as the mentos and diet coke demonstration. Mentos are rough and they are a nice site for a bubble nucleation and you get that as the bubbles all accumulate on the mentos if you drop them in quickly. You 
want to try it? 

Mara: Let's do that! Let's do it!  

[Video cuts to outside on the driveway. Music plays while Mara puts Mentos into a 2L jug of diet Coke. A stream of Coke erupts from the jug. Mara gives two thumbs up.]

[Video cuts back to inside at the kitchen bar.]

Joanne: Okay so that was fun, blowing up diet coke with mentos using nucleation on the rough mentos! What do you think? 

Mara: It was fun but I feel like it could be jazzed up a little more. 

Joanne: Jazzed up? That wasn't jazzed up enough for you? You need it amped up more? 

Mara: Yeah! 

Joanne: What are you thinking? 

Mara: I'm thinking like you know those machine things where it's like dominoes hit like a ball or something and then it hits something? 

Joanne: Oh yeah yeah, like a rube goldberg machine. 

Mara: Yeah, yeah, yeah, those things. 

Joanne: You want to Rube gGoldberg machine a diet coke and mentos demonstration?  

Mara: Yeah! 

Joanne: I like the way you think. Let's do it! 

[Video cuts to outside. Mara is holding the handle of a garden hose.]

Mara: Okay so this is my Rube Goldberg machine um... to blow up a bottle of coke. We're gonna start by shooting the weathervane with the hose um and then it's going to hit the Jenga blocks. I've taken out pieces in case they get knocked over by accident.  

Umm... then they're gonna hit the ball into the bucket and these buckets are balanced so when the ball goes in, this one will go down. This one will go up and when this one goes up it'll lift the gate and let the car go down the track and then it's gonna fly through the air and 
hit this post which is gonna let the ball swing and hit the chicken and when the chicken 
gets hit off the teeter totter these mentos are going to go down the tube and 
into the coke bottle and then explode.

[Mara starts the machine by spraying the weathervane.]

Mara: OOOOHHHH!

[Diet Coke explodes out.]

Joanne: Woohoo!!!

[Laughing]

[Music plays during a slow-motion replay.]

[Video cuts back into kitchen bar. Joanne is blowing a bubble with her gum.]

Mara: Thanks for watching Ask Me Anything: Science Edition. 

Joanne: And don't forget to send us your questions if you have something that you're wondering about!

[Both blow bubbles with gum]

Mara: Have a science-tastic summer and blow lots of bubbles!

[Mara pops Joanne’s bubble.]

Mara: Hahahah, I popped your bubble.