 Hi, my name is Illiana and I'm here at the MIX Latin Center at the San Francisco Public Library ready to be your host for the STEM Challenge Yourself series. In this series, we have some of our librarians sharing some fun and creative projects that you could try at home. Today's challenge master is Joseph. He's from the bookmobile and you may have seen him riding around San Francisco showing off some really cool tricks. I think you're up for the challenge. Ready? Hello, friends! Hi! Today, I will show you how to control the flow of water just using force, invisible force. Are you ready? All you need is a glass or a jar of water and a cardstock. To begin, place your cardstock on the mouth of the jar with your palm, hold the cardstock. If the jar is a little bigger than your palm, try using another material to hold it. But since I have a bigger palm, I'm just going to use my palm and flip the jar. What do you think is going to happen? Everybody? Are you ready for this magic trick? And one, two, three, upside down! And hold it for a few seconds. And let's see if this works. One, two, three. Whoa! So what is happening? Let's take a look at this illustration here. And here's our upside down jar. And we have our cardstock holding the jar. And this is our water here. So what's happening? This invisible force called atmospheric pressure. It's creating all this force, bumping onto the paper, holding the water and the cardstock on place. And what else is happening? We have adhesion. What is adhesion? So let me grab us a paper here and just wet it. And there you have it. I was able to stick this paper onto this material. We're just using paper. And it's exactly what's happening on the surface with the cardstock. The water and the cardstock are creating this like a glue. What else is happening? We have this phenomenon called surface tension. The water molecules inside here, they're attracted to all the other water molecules everywhere. So they're confused. Should I go up? Should I go down? But the water molecules on the surface, since there's no other water molecules below them, they're attracted to their neighbor, creating this awesome vine and allowing the water to stay inside. This is such an awesome trick to try at home. And may the force be with you. Back to Ileana. Thanks Joseph. May the force be with you indeed. That was some really cool that you can do some water bending with a jar, water and cardstock. Be sure that you have a bowl or a tray to catch that water in case things get a little wet. For more information about this stem challenge yourself and lists that we have available for you, check out sfpl.org. So keep experimenting at home and stay stem-tastic.