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Duration:03:27
Uploaded:2015-05-11
Last sync:2018-05-04 20:50
A SciShow Kids viewer wrote us and asked: How does soap work? Find out what really happens when you take a bath!
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SOURCES:
Source: http://www.ck12.org/physical-science/Mixtures-in-Physical-Science/lesson/Mixtures/
Source:https://www.aad.org/dermatology-a-to-z/for-kids/about-skin/taking-care-of-your-skin/washing
Source, and a nice drawing of the micelle around an oil particle:http://www.planet-science.com/categories/under-11s/chemistry-chaos/2011/06/soap---how-does-it-get-things-clean.aspx
(Intro)

You know the very best way to learn something? By asking questions! No one know everything after all, so if something comes up that you just don't understand, ask someone that you think could help. 

I've been thinking about this because of a friend, the giant squid. A couple of weeks ago we were talking about why things float in the water, and I said that some things float in the tub when you're taking a bath other things don't. But Squid lives in the ocean and he doesn't take baths, so he asked me what baths were, and why we take them? 

Squid: What's a bath? 

Jessi: Well, up here, we like to clean ourselves by soaking in a tub of nice, warm soapy water. 

Squid: That sounds gross! Do you mean that humans just walk around all day getting dirty?

Jessi: And you know what's really great? After one of our viewers, Zoe, saw that episode she thought of another question. So she wrote to us and asked 'How do baths work? And how do soap and water get us clean?' Another great question.

First, water's good at dissolving a lot of things. When I say water dissolves something, I mean that it breaks it down into smaller pieces that get mixed in with the water. So for example when you rinse your muddy hands under a running faucet, two things happen. One, the force of the water pushes the mud off of your hands, and two, the water dissolves some of the stuff that makes up the mud and washes it down the drain. Cool right? But what about baths? 

Before we can dive into that, we should probably take a quick look at how we get dirty in the first place. Your skin makes its own oil, This natural oil helps your skin stay soft and healthy. And your skin also makes sweat which we've talked about before too. Sweat is mostly salt and water. When the water in your sweat dries up, it helps cool your body down. But it leaves that salt and other stuff behind. So all during the day, dirt and dust sticks to the salt and oil. If you let the dirt and oil build up for too long, it becomes a good place for bacteria and other very tiny living things. So it's a good idea to wash often.

Now when you get in the tub, the water dissolves the salt and a lot of the dirt that gets stuck on your skin. But one thing water can't dissolve is the oil itself. Why? Because oil and water just don't mix! You can see so for yourself. If you pour some water in a glass and add a bit of cooking oil, you'll see that they dorm two completely different layers. Water particles are small, and stick together very tightly. But oil particles are bigger, and don't stick together as well. So if water can't mix with oil to wash it away, then how can you get that oil off of your skin? 

That's where soap comes to the rescue! Soap can't dissolve oil, but it can stick to it really well and help wash it away. If you could look at the particles that make up soap, you could see that they each have two different ends. And each end is attracted to or pull toward different kinds of things. One end of the soap particle is pulled toward water, and the other is pulled toward oil. So when you mix soap with oil and water, one side of each little soap particle sticks to the oil, while the other side sticks to the water. And then when you rinse off, the soap, oil and water all go right down the drain.

So now you know how water and soap work together to get us squeaky clean in the tub! And if you happen to see Squid before I do, tell him yourself! 

Thanks for asking all these great questions. Do you have a question that you would like us to answer? If you do just let us know by sending us an email at kids@thescishow.com. Thanks guys, and see ya next time! 

(Outro music)