(Intro)

Ahh, summer break.  Don't get me wrong, going to school is great.  You get to hang out with your friends every day and learn all kinds of new things, but the summer is also pretty amazing, and one of the best things about summer is that it's warm enough to do science experiments outside.  One super fun thing to do outside is blow tons of bubbles.  Bubbles might seem simple.  They just float around for a little bit and then pop, but there's a whole bunch of science going on in the short life of a bubble.

Today at the Fort, we’re blowing bubbles!

This is an official summer fun alert! If you’ve had a chance to blow bubbles at school, or in your backyard, then you know that it can be really fun to make them — and pop them!

And they’re also a pretty cool way to learn some science! First, let’s practice blowing bubbles! To blow bubbles, you need two things: bubble liquid, which is mostly made of soap and water, and the stick you blow the bubbles out of, which is called a wand.

I’ll dip my wand into the bubble liquid and blow—but not too hard! If I blow too hard, then I’ll blow the liquid right out of the wand. But if I gently blow a steady stream of air through the bubble liquid … and I get a bunch of bubbles!

Bubbles are really just a thin layer of soap and water around a pocket of air. If we could cut a bubble in half and look at it really closely, we would see that the bubble is actually made up of layers. There’s a layer of water between two layers of soap.

It looks kind of like a sandwich! The soap layers are like the bread of a sandwich, and the water is like the sandwich filling. The layers of the bubble surround the air inside the bubble, and keep it inside.

Water without soap doesn’t make bubbles very well, because water likes to stick together. Water’s made up of lots of little tiny pieces, or particles, so small that you can’t even see them. But they’re there!

These particles are attracted to each other, meaning that they’re pulled toward each other like magnets. So they stick together! For example, check out this insect!

It can walk on the top of this pond because the particles that make up the water in the pond are all attracted to each other. They stick together so much that the insect can walk on the water without falling in! The little particles in water are pulled together so strongly that they can’t spread out into a thin bubble with air inside.

The water in the bubble would just pull back together into a droplet! But when you add soap, it helps the water spread out without being pulled back together, by making that soap-and-water sandwich. And you get bubbles!

There’s something else that’s special about bubbles. Bubbles can be lots of different sizes, from super tiny to gigantic. But have you noticed that they’re all the same shape? [Squeaks squeaks] That’s right — they’re round!

Just like the wand we used to blow the bubbles. What would happen if we used a wand that has different shape? Like this one! [Squeaks squeaks] Right, Squeaks! [can change triangle to square or rectangle or whatever shape it actually is] This wand is shaped like a triangle.

So, what do you think will happen when I blow bubbles out of this triangular wand? [Squeaks thinks they’ll be triangular] You think they’ll be shaped like a diamond? OK, let’s try it and see what happens. When I dip the wand into the bubble liquid and blow … the bubbles are still round!

Even though the wand I blew the bubbles out of /wasn’t/ round. It’s round because of that water layer, the filling of the bubble sandwich. Even though the soap helps the water spread out into a bubble by making the particles in the water less attracted to each other, they’re still a little bit attracted to each other.

And when the water particles pull on each other around the air inside, they give the bubble its round shape. Even if our wand has corners, the attraction in the particles that make up water pull those corners out, and give us a nice round bubble every time. [Jessi blows some bubbles to demonstrate. Squeaks pops them.] I guess you like popping bubbles, Squeaks! [Squeaks agrees] I do too!

It’s really fun. But do you know /why/ they pop? If something manages to break the attraction between the water particles that make up the bubble’s water layer, like Squeaks’ nose or my finger, the air is able to get out, and the bubble pops!

It’s a lot like popping a balloon with something sharp. When you poke a hole in a balloon, the air gets out and the balloon pops. When you touch a bubble with your finger, you’re basically poking a hole in the bubble.

Want to pop some more bubbles, Squeaks? [Squeaks nods and squeaks] OK, let’s head outside and blow some more bubbles!

Yeah, you could blow bubbles inside, Squeaks, but outside, they float around in the wind and you have more room to blow gigantic bubbles.  Another thing that's more fun to do when it's nice and warm outside is fly a kite.  Can you imagine being outside on a cold, windy, winter day, running through the snow to try and get your kite in the air?  Brr.  And a great thing about kites is that you don't have to go buy one.  You can make your own with a little help from a grown-up.  

It’s a beautiful day, so Squeaks and I were just about to go to the park and do one of our favorite summer activities: fly kites!

Kites come in all shapes, sizes, and colors! You could buy them at a store, but Squeaks and I really want to build our own!

Most basic kites are big and flat, with a long tail. They’re connected to a long piece of string, which you hang on to so you can control how they fly. [Squeaks squeaks] How do kites fly? That’s a good question, Squeaks!

There’s more to how a kite stays up in the air than you might think! It all has to do with that big, flat part of the kite, which is called the sail. As the kite flies through the air, the sail is tilted, so the back of the kite is a little bit lower than the front of the kite.

That tilt is really important for keeping the kite in the air, because it changes the way the air flows over the sail. As the air flows past, it pushes on the sail. But because the kite is tilted, the air rushing past the bottom of the kite pushes up on the kite harder than the air flowing past it on the top.

With the air pushing up on the bottom of the sail, the kite can stay in the air without falling down. But there’s something else that helps kites stay up in the air, besides the big flat sail. Can you guess what it is, Squeaks? [Squeaks squeaks] That’s right!

That big, long tail! The tail weighs down one side of the sail, which keeps the kite tilted so the air rushes past it in just the right way to push up on the kite and keep it flying. Squeaks, now that we know how kites fly, are you ready to build our own? [Squeaks squeaks] OK, let’s do it! [to viewers] You can build your own kite at home, too!

Just make sure to ask a grownup for help with this. You'll need a heavy plastic sheet that you can cut, like a very strong trash bag. We're going to use a plastic table cloth!

You’ll also need two dowels, which are basically long, straight wooden sticks. You'll also need a very long piece of thin string or yarn for a line. At least 100 meters, or 300 feet, would be good.

The more the better! Plus, you’ll want a piece of wood or cardboard to wind the string around and hold on to. And, of course, we’ll need some strong tape, like duct tape or packaging tape, to hold it all together!

You’ll need a ruler, scissors, and a marker, too. If you’re using black plastic for the sail, make sure the marker is a color that you’ll be able to see, like silver. Ok, Now that we have all the supplies we need, we’re ready to make our kite!

Lay the dowels across the plastic in a cross shape, with one of the dowels a little higher so one half is longer than the other. Use your ruler to draw a diamond around your dowels, like this. It’s good to make sure the diamond is a little bit bigger than your dowels to make sure it fits.

Next, have a grownup help you cut the diamond out of the plastic. You can trim the edges of the plastic if it’s a little too big. Now you can tape the dowels to the plastic.

Make sure they’re stuck on really well! We’ll need them to help the sail keep its shape in the wind. Now tape the dowels together in the middle.

Poke two holes in the plastic along the dowel that goes across the kite lengthwise. They should be close to the corners, but not all the way at the end of the dowels. Cut a smaller piece of string, about two times as long as one of the dowels.

Next, flip the kite over and thread one end of the string through one of the holes and tie it to the dowel, and do the same thing with the other end of the string and the other hole. Tape the ends of the string in place to make sure they stay put! Now, take one end of the rest of your string and tie it to the shorter string, right in the middle.

You should tape that together too. Finally, wind the rest of the string around your wood or cardboard handle. Our kite is done! [Squeaks squeaks] Oh, that’s right!

We need a tail! Cut out a long, thin piece of the plastic and tape it to the bottom of the kite. OK, now our kite is really done!

To fly it, all we need to do is go to a big, open area outside on a day that’s a little windy, but not too windy. It’s easiest if you have a friend or grownup to help! Hold on to the handle with the string wrapped around it, and have your friend hold on to the kite.

Unwind about 20 meters, or 60 feet, of the string and stand far enough apart from your friend so that the string is straight and not hanging down too much. Your friend should stand with their back to the wind, holding the kite by where the strings are tied together. Next, they should let go of the kite so the wind can push it up, while you pull on the string to get it going!

It might take you a few tries, but in the end, you’ll get your kite flying! Alright, Squeaks! Let's go fly our kite!

A nice sunny day like today is the perfect time to do one of our most amazing experiments.  You might already know that the warmth from the Sun is a kind of energy, and that people can use that energy to do all kinds of stuff, like power their homes, and Squeaks and I came up with an awesome invention you can use to see the Sun's energy in action.

It’s a beautiful, sunshiny day where we live!

My favorite thing about a nice day like this is feeling the warm sun on my face. But did you know, aside from just feeling nice, the sun’s warmth is a kind of energy? (Squeaks squeaks) You’re right, Squeaks!

We use energy from the sun’s light and heat for lots of things! When you use the energy from the sun, that’s called solar power, because “solar” is just another word for things that come from the sun. Have you ever seen a bunch of big, flat, black rectangles on top of a building?

Those are solar panels. They take sunlight and turn it into electricity! Some people also collect the heat from sunlight to warm their homes or heat their water.

I even built Squeaks to run on solar power! Maybe Squeaks is wearing a pair of sunglasses or something) You know, Squeaks, this warm, sunny day got me thinking about a cool project we can do together to use the sun’s energy ourselves. Want to try it? [Squeaks agrees] Okay, let’s do it! We’re going to build something called a solar updraft tower.

Since it has the word “solar” in it, you already know that it has something to do with the sun. “Updraft” just means a kind of wind where air moves up. And you know what a tower is! So, can you guess what our solar updraft tower will do?

It’ll take sunlight, and use that to make air move upward through the tower and spin this paper pinwheel! You can try this project at home, too. First, you’ll need three clean tin cans that with the tops and bottoms cut off.

Make sure to get a grownup to open the cans! You’ll also need some tape, a paper clip, a thumbtack, and two books that are about the same thickness. They should be pretty big books.

Then, ask a grownup to cut a piece of paper into a square, 15 centimeters — or about 6 inches — on each side. And, most importantly, you need a sunny day! Now we’re going to build the tower.

First, stack up the cans and tape them together really well. Next, bend the paperclip into an arch shape like this, and tape it to the top of the tower of cans. Then, get a grownup to help you attach the thumbtack to the top of the paper clip shape with tape, like this!

Now, we’ll fold the pinwheel. Grab your square paper and have a grownup help you cut diagonally from the corners. Don’t cut all the way through the paper, though!

Stop cutting about this far from the middle. Once all the corners are cut, fold them like this, and tape them together in the center. Done!

Then get your grownup to stick the pinwheel onto the pointy end of the tack. Our tower is ready! All we have to do now is put the can tower on top of the books, so there’s a gap at the bottom, and set the whole thing near a window, where there’s direct sunlight — so the sun is shining straight through the window.

And now we wait. It might take a while, depending on how warm and sunny it is where you are, so be patient and check on your tower every now and then. After a while, something really cool will happen!

Whoa! The pinwheel is spinning! (Squeaks squeaks) It isn’t magic, Squeaks! It’s science!

When the sun shines on the cans, the cans get hot. Some of that heat travels through the metal to the inside of the cans, so there’s hot air inside the tower. And hot air rises.

Squeaks, do you remember when we learned about how hot air balloons work? Well, this is the same kind of idea. Air might seem like it’s made of nothing, but it’s actually made of lots of little tiny particles, way too small to see.

When sunlight heats up the air inside our tower, the heat makes those tiny particles start to bounce around faster and spread out. Warmer air that’s more spread out like that will move upward so it’s on top of the cooler air that’s less spread out. It’s a lot like how a plastic spoon will float on water!

In our tower, that means that when the sun warms up the air inside the cans, the warmer air will move upward through the tower and make the paper wheel spin as it passes by. Then cooler air comes in through the gap on the bottom of the tower, gets heated up, and rises, so there’s a constant flow of warm air that keeps the wheel spinning. We’ve made a solar updraft tower.

There are some places in the world where they actually use giant solar updraft towers to generate electricity! So the next time you feel the warm sun on your face, remember that it’s more than just a nice feeling — sunlight is a powerful and useful source of energy. It’s the same energy Squeaks uses to get around!

Woof, that is a lot of science for one day.  I think we deserve a treat.  How about you?  Well, I have one more super special, super scientific experiment in mind, one where we'll make something that'll hit the spot on such a hot day.  Can you guess what it is, Squeaks?  That's right.  Let's whip up some ice cream with science.

Woo!

It’s getting hot out! Squeaks and I are craving ice cream, but we don’t have any.

So, we’re going to make ice cream using science! We know that ice cream is made out of cream and sugar and a flavor. And we know that it’s frozen, but it’s not rock hard like plain ice.

It’s more like very cold whipped cream! So, we have cream and sugar. We also have vanilla that we’ll flavor our ice cream with.

And now we’re going to take these three ingredients and turn them into ice cream! And you can do this at home, too. You’ll need your three ingredients: sugar, vanilla, and cream.

Or you can use milk or half and half instead of cream. You’ll also need a measuring cup, measuring spoons, oven mitts or a towel, a small sealable plastic bag, a large sealable plastic bag, ice cubes, a timer, and a grownup to help. The last thing you’ll need is the important one: salt!

First, take your three ingredients and put them into the smaller bag. We’re using a half cup of cream, a half teaspoon of vanilla, and a tablespoon of sugar. And then, seal up that bag.

Next, put ice into the big bag. We’re putting four cups of ice in. That’ll make the cream cold.

But, here’s the amazing scientific part! We’re going to add salt to the ice. We’re adding half a cup of salt.

It’s important to add salt to the ice, because that will make the ice cream freeze much faster. Here’s why: If you’ve ever put out salt on your sidewalk or driveway in the winter, you know that salt can melt snow. That’s because when there’s lots of salt in water, it needs to be colder than plain water does to freeze.

Even if it’s cold enough outside for /plain/ water to freeze into snow, it’s probably not cold enough for /salty/ water to freeze! So when you add salt, the salty snow melts. When you add salt to the bag of ice, the same thing happens.

The ice is cold enough to freeze when it’s just plain water. But it’s not cold enough to freeze when there’s lots of salt! So the ice cubes in the bag start to melt!

That melting is /really/ important for making your ice cream really cold, really fast. Because as the ice melts, it draws in heat, making the things around it much colder — including your ice cream! So, now that we’ve added salt to our bag of ice cubes, the ice is going to start to melt and make the cream, sugar, and vanilla in the smaller bag REALLY cold.

While that’s happening, we’re going to make sure the ingredients in the bag become ice cream! This is where we need our oven mitts or a towel because this bag is really cold. Protect your hands and hold onto the bag.

Now we’re going to shake it! It’s good to have a friend to help you with this part. Squeaks and I have made butter before, and we shook up the cream until it got hard and turned into butter.

But before it turned into butter, it was soft and fluffy whipped cream. Ice cream is harder than whipped cream, but softer than butter, so we’ll have to shake our cream /longer/ than we would to make whipped cream, but /not/ as long as we would to make butter. There are tiny pieces of fat in the cream, and as we shake the bag, they’ll start to clump together until the mixture becomes thick and creamy, just like ice cream should be.

If our salt water solution is as cold as if feels, that should take about five to ten minutes. Ready, Squeaks? It’s getting there!

It looks like whipped cream now. Just a little bit longer. It’s looking a lot more like ice cream to me.

Let’s open it and check. Make sure you have a spoon handy to taste test! What do you think, Squeaks?

Tastes good to me! We did it! And we hope your science ice cream is delicious too!  Make sure to ask a grown-up to help you with your experiments and share your results.  

Alright, Squeaks, we've got our kite all ready, our sunscreen on, and some ice cream to keep us cool.  I think we're ready to go out for some fun in the sun.  We hope you all have a great summer break full of fun and learning, and if you try any of these experiments, we'd love to see pictures.  Grab a grown-up to help you leave a comment down below or send us an email to kids@scishow.com.  Thanks and we'll see you next time here at the Fort.

(Endscreen)