Raindrops fall on the Elbsee lake near Aitrang, southern Germany, on October 13, 2014.

If you filled a lake with lemonade, would it rain lemonade? This delicious head-scratcher does not have a straightforward answer, so we asked atmospheric scientist Deanna Hence to help out with this thought experiment. It’s one-part water cycle, one-part delicious drink and if we’re lucky, one-part lemonade rain.

Want to learn more about the water cycle? Check out this episode!

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MOLLY BLOOM: You're listening to Brains On from NPR News and Southern California Public Radio. We're serious about being curious. I'm your host Molly Bloom. Today we're going to take a slight twist on this.


That's right. Rain. Nine-year-old Izzy is kind of an expert on the subject. She's from Seattle. And in addition to coffee, computers, and throwing fish, Seattle is known for rain. Izzy has an interesting thought experiment about a very special kind of rain.

IZZY: If there is a lake of lemonade and it evaporated, would it rain lemonade the next day?

MARC SANCHEZ: Good question, Izzy. And now I'm a little thirsty.

MOLLY BLOOM: That's producer Marc Sanchez expressing his need for lemonade. Hello, Marc.


MOLLY BLOOM: So how did you track down the answer to Izzy's question? Did you actually fill a lake with lemonade?

MARC SANCHEZ: Oh, I wish I did. I wish I could. But sadly, no. And since we don't have the time or money to fill a lake with lemonade, we're going to have to build one in our minds.

First, let's agree our lemonade is going to be made of three simple ingredients-- lemon, sugar, and water.

MOLLY BLOOM: Sounds delicious already. Go on.

MARC SANCHEZ: A normal recipe yields two quarts of lemonade, but we'll need to fill an entire lake.

MOLLY BLOOM: How big is this lake?

MARC SANCHEZ: Well, I was thinking about this, and I live in Minneapolis near a pretty big lake called Lake Harriet. And since we can't drain that and fill it with lemonade, I was thinking we could at least go off its size. So I found out that Lake Harriet has a volume of about 10,134 acre-feet.

MOLLY BLOOM: So in lemonade, that would be--

MARC SANCHEZ: One acre-foot is equal to 1,303,000 quarts.

MOLLY BLOOM: Whoa. So in order to fill 10,134 acre-feet--

MARC SANCHEZ: We'll need 13 billion 200 million quarts of lemonade.


MARC SANCHEZ: Which means we'll have to make our recipe 6 billion 600 million times over. So we have a lake full of lemonade, and now we just need a quick recap on how it rains normally.

MOLLY BLOOM: We actually did a whole episode on the water cycle.

MARC SANCHEZ: A quality episode, indeed.

MOLLY BLOOM: And in it we learned that water is continuously being transformed from a liquid to a gas.

MARC SANCHEZ: In the ground, in your sink, in an ocean or a lake, that's liquid.

MOLLY BLOOM: But when it heats up, say by the sun shining down on a lake, that water evaporates and changes into a gas.

MARC SANCHEZ: Those tiny gas molecules rise up into the air.

MOLLY BLOOM: As the air cools, trillions upon trillions of those molecules bump into each other and join together in the air.

MARC SANCHEZ: And we see them as clouds in the sky.

MOLLY BLOOM: When enough molecules get together in the clouds, they form drops of rain that are heavy enough to fall back to Earth.

MARC SANCHEZ: Thank you, gravity.

MOLLY BLOOM: And then the whole thing starts over again. That's why it's called the water cycle.

MARC SANCHEZ: Now that we know how it rains, it's time to introduce Izzy's lemonade lake to a weather pro.

MOLLY BLOOM: Deanna Hence is an assistant professor of atmospheric science at the University of Illinois at Urbana-Champaign.

MARC SANCHEZ: Let's go to Izzy one more time.

IZZY: If there is a lake of lemonade and it evaporated, would it rain lemonade the next day?

DEANNA HENCE: This is actually a question I had to think a fair amount about. And I actually had to ask some of my chemist friends to help me with this one. The short answer is no, you probably would not get lemonade rain.

MOLLY BLOOM: Oh, that's disappointing.

MARC SANCHEZ: That's a bummer.

MOLLY BLOOM: What are we going to do with the rest of this episode?

MARC SANCHEZ: Go swim in a regular lake or something? I don't know.


MOLLY BLOOM: Oh, good, there's more.


DEANNA HENCE: --what we may end up with actually is what makes this problem kind of interesting.

MARC SANCHEZ: OK, so typically when you evaporate a solution that has water, say, salt water or sugar water, the water would evaporate just like we talked about in the water cycle. So if you did this in a laboratory with sugar water or salt water in a dish, let it evaporate, you'd end up with salt crystals or sugar crystals in that dish.

DEANNA HENCE: When we think about with lemonade, part of the answer is that sugar and that water that you would have added to the lemon juice to make lemonade, the water would evaporate, but the sugar would be left behind. But the interesting thing is about this is that we have to consider the lemons as well.

MARC SANCHEZ: And here she's talking about the chemical makeup of lemons.

DEANNA HENCE: So lemons are also full of water, sugar, but also the acids that make them tart. And all plants have minerals that help them grow, so there's also minerals in them as well. That mixture of sugar, acid, and the minerals would get more and more concentrated and would get more and more acidic as the water evaporated. And eventually you'd get left with this sticky goo.

MOLLY BLOOM: All that hard work filling a lake with lemonade, and all we're left with is sticky goo.

MARC SANCHEZ: A little disappointing, I know. But wait. Deanna says there's something more to think about.

DEANNA HENCE: There is another part of lemons that we also have to consider, and this gets into how exactly that lemon juice was made.

MARC SANCHEZ: In a few minutes, Deanna's going to explain how the way we make lemonade factors into the equation. But right now we have an announcement.

MOLLY BLOOM: The next Brains On debate between producer Sanden Totten and Marc Sanchez has been chosen.

MARC SANCHEZ: Team Sanchez!

MOLLY BLOOM: That's not fair.

MARC SANCHEZ: Sorry, I'm biased.

MOLLY BLOOM: And the topic is fire versus lasers.

MARC SANCHEZ: Hey, Molly, can we try that one more time and maybe do it a little more ramped up and a voice that's kind of supposed to fill a stadium. You know, (DRAMATICALLY) fire versus lasers, ah!

MOLLY BLOOM: OK, how's this? (DRAMATICALLY) Fire versus lasers!

MARC SANCHEZ: That's not bad. But if I'm going to enter the debate arena with Sanden Totten, I need to be a little more pumped up. How about this?


(DRAMATICALLY) Get ready for the next Brains On debate-- fire versus lasers. That's right. Just in time for Thanksgiving, producers Sanden Totten and Marc Sanchez will do battle. Well, debate battle. Anyway, cheer on Marc and Sanden in this November's debate-- fire versus lasers.

MOLLY BLOOM: OK, I get it now. So if you have strong feelings about either side of the debate, send them our way.

MARC SANCHEZ: Just tell us if you're with team fire or team laser, and let us know why.

MOLLY BLOOM: Send your email to brainson@M, as in Minnesota, PR.org. And I know one team that everybody can agree on.

MARC SANCHEZ: And that is?

MOLLY BLOOM: Team mystery sound.


CREW: (WHISPERING) Mystery sound.

MOLLY BLOOM: Here it is.


MARC SANCHEZ: That is a tough one.

MOLLY BLOOM: Do you want to hear it again?



MOLLY BLOOM: What do you think?

MARC SANCHEZ: It could go two ways. I've got one guess that says we're listening to paranormal activity.


And I'm kind of scared out of my wits right now. Or there's another one that tells me maybe it's some sort of outdoor nature sound with possibly a bug and possibly some water, but I don't know. I'm kind of stumped.

MOLLY BLOOM: OK. You're closer with the second one. Here is Char--

MARC SANCHEZ: No ghosts?

MOLLY BLOOM: No ghosts. Here is Charlie from Sydney, Australia with the answer.

CHARLIE MORGAN: Hi. My name is Charlie Morgan, and I'm 6 years old. I live in Sydney, Australia. I have a worm farm in my garage.

MOLLY BLOOM: That's worms in his worm farm.

MARC SANCHEZ: What? I heard buzzing.

MOLLY BLOOM: Well, there was a fly around the worm. But that sort of like [SLURPING]

MARC SANCHEZ: It wasn't water.

MOLLY BLOOM: It was worms.

CHARLIE MORGAN: We have the worms, not for me to play with, but to use up our fruit and vegetable scraps and to make compost and worm tea, which is the liquid which helps plants to grow. The worms don't like all fruit and vegetables. They don't like lemon, orange peel, or garlic. But they love potato peel.

We give them a lot of water and sprinkle eggshells on them. And my mom think there's about 10,000 of them. It looks like there's at least a million when I lift up the lid to feed them.

MARC SANCHEZ: A million-worm worm farm.

MOLLY BLOOM: Well, to be fair, closer to 10,000, according to his mom, but that's a lot of worms.

MARC SANCHEZ: That is a lot of worms. At first I was thinking, worm farm? What are they growing? Tiny worm corn? But then--

MOLLY BLOOM: No, they're making compost and worm tea for the plants in their garden.

MARC SANCHEZ: They're going to enrich the soil to grow amazing vegetables.

MOLLY BLOOM: You can actually hear more about how worms help soil in our soil episode. So thanks so much, Charlie, for sending that in. And you can see a video of feeding time on Charlie's worm farm if you head over to our Instagram. That is brains_on.

If you have a mystery sound or question for us, you can email it to us at brainson@M, as in Minnesota, PR.org.

MARC SANCHEZ: And if you search for brains_on, you can find us on Twitter and Instagram. You can look us up on Facebook, or if you want to send us a regular old envelope, go to brainson.org and find our address.

MOLLY BLOOM: And now it's time to celebrate some of the most curious, interesting, wacky, fantastic, and engaged minds that we know of. High fives and huzzahs to the latest edition of the Brains Honor Roll.




MOLLY BLOOM: We are back, and I for one am ready to find out if there could be such a thing as lemonade rain.

MARC SANCHEZ: Yep. And if I'm being honest, I didn't think such a thing was actually possible. And atmospheric scientist Deanna Hence wasn't really giving me much hope until she said this--

DEANNA HENCE: There is another part of lemons that we also have to consider, and this gets into how exactly that lemon juice was made.

MARC SANCHEZ: Have you ever felt a lemon, just on the outside?


MARC SANCHEZ: You know how it's kind of got that waxy feeling?

MOLLY BLOOM: Yeah, and it has a nice smell too.

MARC SANCHEZ: Yeah. That smell and that feeling, that could be the key.

DEANNA HENCE: Lemons, in their skin, actually have quite a lot of oil in them. That's the stuff that leaves that fresh scent. And those oils are actually what are known as highly volatile, which means they actually really easily evaporate into air. So depending on how that lemon juice was pressed, that could leave some amount of that lemon oil in the lemon juice.

So as that water was evaporating, those really volatile oils would also start to vaporize. And if that water was warmed up at all, especially, say, by the sun, then that would actually help those oils vaporize even faster.

MARC SANCHEZ: And we know the hotter the heat source--

MOLLY BLOOM: The faster evaporation occurs.

MARC SANCHEZ: Right. Now get this.

DEANNA HENCE: If the water from that evaporating lemonade was able to rain through all that vaporized oil, raindrops actually have an ability to what we call scavenge particles out of the air. So it's possible that those raindrops could actually pick up some of that vaporized oil.

MARC SANCHEZ: Those two simple words, "it's possible."

DEANNA HENCE: I grew up in Texas. Sometimes when air would be really dusty and we'd get a rain shower through that dust, it would actually look like it rained mud because the raindrops actually picked up all of those dust particles and then took them with them as they headed towards the ground and then splattered that dirt all over the place.

So raindrops have the ability to do this, so possibly it could pick up those oil particles out of the air and then bring it back with it as rain. So even though you wouldn't end up with lemonade, you might get some very lightly-scented lemon-scented water, which also sounds nice to me.

MOLLY BLOOM: That does sound nice. I would like a nice lemon-scented rain.

MARC SANCHEZ: Well, it's not going to taste like the sweet lemonade you're used to, but still, lemon water falling from the sky. Deanna says there's one more factor that we should take into account.

DEANNA HENCE: I mentioned how volatile these lemon oils are. They also easily react with air. And they actually react pretty fast. So it's possible that within about an hour, the lemon oils would change into something else as they reacted with the oxygen in the air. So this rain shower would have to happen pretty fast.

MARC SANCHEZ: So under the right conditions--

MOLLY BLOOM: Like a lake full of lemonade that has lemon oil in the water.

MARC SANCHEZ: And a water cycle that takes under an hour.

MOLLY BLOOM: It could rain lemonade.

MARC SANCHEZ: Or at the very least, lemon-flavored water.

MOLLY BLOOM: If you want to hear more from Deanna Hence, you should check out the Brains On archive and listen to our episode about how meteorologists predict the weather.

MARC SANCHEZ: You know, Molly, Deanna really got a kick out of this thought experiment. And she says considering imaginative ideas like this can be really useful.

DEANNA HENCE: One thing that's really cool about this particular problem for me is that it really stretched me to think about things that I don't typically think about. On top of that, it also encouraged me to talk to another scientist-- or two other scientists, actually, as it happened to be, to see what they thought about it.

And so one thing that's so great about scientists is when we talk to each other, we can combine our different knowledge and our different skills and come up with whole new solutions to problems that individually we might not have. We get used to looking at the world in a certain way as we get older, and one of the great things, I think, about being a scientist is that it constantly challenges you to look at the world in a different way.

But we are still grown ups, and sometimes we can get locked into thinking a certain way. So it's really great to have someone else come along and challenge that thought to make sure that we don't get stuck for too long.

MARC SANCHEZ: Here's a glass full of lemonade raised to all the questions that start with "what if."

MOLLY BLOOM: That's it for this episode of Brains On. Special Thanks to John Miller.

MARC SANCHEZ: Thanks for listening.

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