This dish of water. And we're going to add some of our little indicators. May recall that bromophenol blue, the indicator we used before to change this stuff goes lumpy, greenish color, which I think what's kind of a bluish color on the screen. But let me just add a little bit of this ammonia solution to make it even more blue. >> Actually, what the heck? >> We're just going to add some straight everyday ammonia which are this stuff getting blood. Obviously Portland now that it wasn't people right now, who knows what this stuff is in the room, you can actually look at it and thank you for watching and oh, and we're going to figure it out on the screen, going once, twice, three times, 3e away. >> I'm going to pass it around so you can inspect it more detail. >> Ha somebody knows who said that. Yeah. >> What does it rise? You never had a chance to check out a piece of dry ice. I'm gonna pass it around on his paper down. >> Now, you saw just a moment ago that I was actually handling the piece of dry ice. And that's usually the most surprising thing that I find for most people when they look at me doing this well above and beyond the fact that I am, of course crazy. >> You actually can touch dry ice. >> Okay? Which one of the things I intend to show you by passing this piece of dry ice. >> Yes, it's very cold. >> Part of the reason that people say you can't touch dry ice is because if you touch dry ice for any length of time, you'll give yourself a case a frostbite, which is why I'm putting it on the paper towel so I can pass it around, people can touch it. >> And all I can say is if you want to handle the dry ice, go ahead and do so. >> But when it starts to hurt, put it yeah. >> What's the best advice I can give you? >> It will start here and just circulated around rooms so everybody gets a chance to check out what a piece of dry ice looks and feels like. >> Now, why is it called dry ice? >> Does anybody know? >> Yeah, it's bakeries rosenthal U2. Basically, when it melts, it becomes okay. >> In other words, let me just offer a slight correction. What she just said. >> You're right, it's made from carbon dioxide. >> Here's another piece over here. >> I can't really see it, so I'll just hold it like this. >> But the point is it does not really melt because by definition, melting means it's going from a solid to liquid, which carbon dioxide doesn't do. >> The term for something changing directly from a solid to a gas is to say that it's supply. >> Now to make that a little bit more obvious, what I'm gonna do is take this piece of dry ice and drop it in the one >> And I hope you can see from some of the bubbles and smoke that's coming up that it actually is going directly from solid state to the gaseous state. >> Now keep an eye on if I'm gonna have to blow smoke out of the way every once in a while. I wanted you to see what color the water is, and hopefully it's obvious that it's still blue. Watch a couple more little pieces of ice here. Heat up the process a little bit. >> Still blue, it's green now. It's green about now or light yellow, kind of a greenish yellow actually. >> But the point is it used to be blue and yellow. >> Those watching at home, I'm kinda going to have to take my word for it, but I hope you can see some of what's now what does that cover change me? >> Well, the ammonia was actually what made it blue. Remember for bromo five all blue. The blue color signifies that it's reacting with a base. >> What is the yellow color being? Yeah, that's what acid-base indicators do. >> They change color depending on whether you mix them with an acid or a base. >> So when we saw a change from blue, which is its basic color, to green, which if it's neutral color to yellow, that means all of a sudden the solution has become acidic. >> What kind of give you a little bit of a hint as to why? And I put that previous slide back up based on the information they gave you a few moments ago. >> Why didn't the color change? >> What's dry ice made from? >> Carbon dioxide? Carbon dioxide is an oxide. >> What? >> Carbon, of course, but carbon is what? A middleware. >> Non-metal, non-metal oxides of Non-metals form acidic solutions. >> Rice is solid carbon dioxide, but when carbon dioxide reacts with water, it behaves similarly to the two previous examples we showed you. >> And it forms an acid called carbonic gas. >> And the point is, once enough of the dry ice reacts with water to form enough carbonic acid to neutralize the ammonia. Then whatever carbonic acid is formed after that just generates hydronium ions when it reacts with work. So once we pile up the hydronium ions at the point where there's more of them than there isn't anything else. That's when the color changes. >> That's that makes sense. Okay.
Dry Ice.mov
From Dana Chatellier March 03, 2020
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