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We've learned before here on SciShow Kids how boats can float on water using displacement! Today, Bill and Webb will show you how to build you own boat and see displacement in action! Anchors aweigh!
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Webb: Hi everyone

Bill: If you haven't met us before, I'm Bill.

Webb: And, I'm Webb.

Bill: We visited before on SciShow Kids, where we talked about things that sink and float.

Webb: That's right, and today we're going to experiment and make a boat that floats. And, we're going to test our boat to see how much it can hold before it sinks.

Bill: A friend of ours, the Giant Squidstravaganza, once asked Jessi how boats can float, and we learned that they float because of displacement.

Webb: Displacement is when an objects displaces water, meaning that it moves water aside so it can take up that space.

Bill: A good example of this is when you get in the bathtub. What happens? Well, you get wet, yes, but also, when you get in the tub, the water rises. So, you are displacing, or moving aside, the water, which makes it rise up around you.

Webb: Hope you didn't get the floor wet, by the way. But, now that we got our thinking caps on, let's make a boat. What kind of boat should we make Bill?

Bill: Well, Webb, I always see people paddling around our pond in canoes. So, I think we should make our own canoes.

Webb: Bill, for once, I've got to say, your idea is great! They'll be the best canoes the world has ever seen.

Bill: Yeah, that sounds fun. Let's get some help from our friends, Sophie and Zane, and get started.

Webb: I've got an idea of what we should use: aluminum foil, tape, and some scissors.

Bill: Is that it?

Webb: That's it!

Bill: Great, and if you're going to use scissors like us, make sure you tell a grownup.

Webb: Yup, safety first! Let's start by cutting off a few pieces of foil that we'll use to make our canoes.

Bill: Now, take a piece of foil, and bend it in the middle.

Webb: Then, let's shape the two ends and pinch them so that they point up. You might need to use more foil and tape to get the shape you want.

Bill: You also want the two ends to be taller than the middle.

Webb: Yeah-hoo! We finished our canoes!

Bill: Yeah! Now it's time to test them out. I mean, watching a boat is pretty awesome, but let's see how much they can hold before they sink. To the tub!

Webb: OK, we're going to fill our boats with marbles until they each sink, but you can use rocks, toys, or anything else that's OK to get wet.

Bill: I'll keep track of the number of marbles it takes to make each canoe sink.

Webb: Alright, are you ready, Bill?

Bill: I'm ready, Webb.

Webb: Here we go!

Bill: Wow, look at it go!

Webb: Ye-ha!

Bill: Oh man, is that one going to sink?

Webb: I think so.

Bill: I don't think that one's ever going to sink.

Webb: Woah!

Bill: Wow, can you believe it?

Webb: No way!

Bill: Oh, no! Boat down!

Webb: Oh, no.

Bill: Oh, no, man!

Webb: Let's check out our results. One boat was able to hold 59 marbles, and the other one had 101. Wow!

Bill: OK, but, Webb, I have a question.

Webb: What?

Bill: Why did canoes sink? I mean, we just told everybody that boats float, because they displace water.

Webb:  That's right, they float as long as the amount of water the boat displaces weighs the same as the boat does.

Bill: Oh, I see. When we started to make our canoe heavier, it began to sink a little lower into the water with each marble, and each time it sank lower it displaced, or pushed aside, just a little bit more water. But, when we put in that final marble, our canoe weighed more than the water it could push aside...

Webb: ...and it sank! You got it! So, try making other boats of different shapes and sizes. Do some float better than others? Did you build a boat that could hold more than our canoe did without sinking? 

Bill: If you made a boat and you want to share it with us, just grab a grownup and send us an email to or leave a comment down below.

Webb: We'd also like to thank Google Making Science for helping us make this episode.

Bill: And, thanks for joining us on SciShow Kids!

Webb: Bye!

Bill: We'll see you later!