Short Wave - When Life Gives You Lemons...Make A Battery

Episode Date: February 5, 2021

We're going "Back To School" today, revisiting a classic at-home experiment that turns lemons into batteries — powerful enough to turn on a clock or a small lightbulb. But how does the science driving that process show up in household batteries we use daily? Emily Kwong and Maddie Sofia talk battery 101 with environmental engineer Jenelle Fortunato.See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

Hey everybody, Maddie Safaya here. And Emily Kwong. With another back-to-school episode where we take a basic science concept you may have learned in school, but maybe, you know, never really learned. Okay. This one was inspired by listener Violet Thomas in Utquiavik, Alaska. You're always bringing us back to Alaska, Emily Kwong. Any opportunity to go back, I will take. Violet wanted to know what the plus sides and minus sides of a battery means.

mean. Simple question, but it took me back, all the way back, to science class and the lemon battery experiment. Oh, yeah, yeah, yeah, where you run some wires from a lemon and try to power something like a tiny light bulb. Yes. We love science. Yes, we do. I love a good science cheer quang. Right. So this video is from a science outreach program called Science You, hosted by Penn State. Can you get power from a lemon? Lemons are powerfully sour. That last voice is That last voice is Janelle Fortunato. She is a postdoc researcher at North Carolina State University

doing materials research. And a few years ago, she was teaching these kids how to build lemon batteries. In Janelle's experience, kids get really into this, especially the middle schoolers. They hooked up like 20 lemons, three cups of lemon juice, an apple,

and like three different. light bulbs and a buzzer buzzing and it was it was chaos I was in awe I don't think I just shook my head leave it to kids to come up with something like that yeah I also I interview enough scientists to know that there is a middle schooler that like lives inside every scientist this kind of what if I did this energy you know what I mean yeah so I'm you know I'm the one that's over their shoulder kind of encouraging them you know within the safety guidelines but you know I'm always there instigating them. I believe, yeah, there's some real teacher safety guidelines,

energy there as well, Quang. It's safe to play around with lemons, but not with actual batteries. That is our safety disclaimer for this episode. Hey, man, you know, when life gives you lemons, build a battery, am I right? I'm so sorry. Today on the show, a light bulb moment. Courtesy of the classic lemon battery experiment, how does it provide power,

and what lessons can we glean from lemons in building the batteries of the future? This is Shortwave, the Daily Science Podcast from NPR. All right, Emily Kwong, I remember you did the Lemon Battery Experiment live for like 700 people during a virtual shortwave trivia night. It's true. And I turned a lemon into a battery. Those clock numbers are ticking. I mean, I have done it countless times. It is tried and true.

And, you know, it's pretty easy as far as at-hop. experiments go. Yeah, that's part of why Janelle likes teaching it. You can get all the materials at a grocery store and a hobby shop. So all you need is a lemon. You can use half a lemon or a whole lemon, a penny, so a copper penny, and a galvanized nail coated with zinc. And you'd stick both of those elements into the lemon so that they touch, you know, the pulp and the acid that's in the lemon. The penny and the nail are going to be the positive and negative ends of our battery. That electrons, those negatively charged particles inside atoms, flow between. But you first got to attach a wire to create a closed circuit.

Which makes electron flow possible. Yeah. So electricity is essentially the flow of electrons through a circuit. And these electrons that are flowing through the circuit, they have the capability of doing work. And by work, she means work. like electrochemical work of powering devices and screens and all kinds of other stuff we use. Janelle said, quote, it's electrons world and we're all just living in it. True words have never been spoken.

Okay, okay, let's talk about how the lemon is generating the electric current in the first place and where those electrons come from. Right. So those electrons are generated through a chemical reaction inside the lemon, which parallels what happens in a household battery. The most basic batteries are made up of two electrodes and an electrolyte, like battery acid. That's basically a substance that electrons can pass through. And in the case of a lemon, lemon juice. Yeah, and those two electrodes made of metal are situated on either end of the battery.

Now, in a household battery, those electrodes are built in. But for a lemon, you've got to add those electrodes yourself. Hence, the copper penny and the zinc-coated nail. And why is zinc-coated nail, you ask? Well, using my teacher voice, that's because the zinc reacts with the lemon juice in such a way that the zinc readily gives up electrons, meaning those electrons accumulate on the nail, and the nail becomes negatively charged. Which is really important for electron flow. And copper, our penny, is a material that wants to accept those electrons. Right, and that's what a battery is all about.

You need a charge difference between those electrodes, the nail and the penny. So when you connect a copper wire between the two, electrons flow from that nail that gives up the electrons easily to the penny that wants to accept those electrons. And so those electrons that are being donated by the zinc will travel through the copper wire, through the copper penny. Which relative to the nail has become positively charged. Because of that charge differential. Yep. And the electrons go for a ride. Back into the lemon where the electrons. will react with the protons inside the lemon juice.

And the lemon juice, like you said, is a great electrolyte being acidic. It's full of atoms that are eagerly accepting electrons. And form hydrogen gas. So if you're actually to make this, you'd see hydrogen gas bubbling up out of your lemon battery, which is kind of cool. Mmm, delicious. This whole exchange, by the way, of electrons is called a redox reaction. Yeah, I remember that word for sure.

I remember redox. And the cycle repeats, right? Electrons traveling through the lemon, it becomes a lemon battery. And as we've said, this phenomenon is not exclusive to lemons. Janelle says anything fairly acidic will do. Lemons, limes. We've done apples before. Potatoes are really good. They contain phosphoric acid. And that forms a powerful bridge for those electrons to travel. But at the end of the day, we're talking about a fairly low power, single-use system.

Yeah, I mean, I know from doing these demonstrations, that lemon can only power one of those little lights for like an hour. And it's not an impressive light, let's be clear. Yeah, to put all that in perspective, to power an iPhone 11 pro max for a day would take 50,000 lemons, assuming optimal lemon performance. Janelle calculated it for me as a fact-checking favor. Honestly, time well spent. I'll say it. You know? But it would take so many lemons, a ton of nails, a ton of pennies. It would be a mess.

So what's amazing about a household battery, let's take a minute to appreciate, is that all you need for that chemical reaction to go down is housed inside the battery itself, right? And modern batteries are powerful. They're long-lasting and more and more are designed to be rechargeable. Yeah, I mean, it is a stunning invention if you think about it. Like storing potential energy, little energy in the pocket. Come on. Something we're improving upon every year. We're kind of in the middle of a battery revolution.

You know, if you were to look in the science literature, even just five years ago, like the pace that battery research is moving is pretty incredible. Yeah, we've got, you know, batteries power in cars, storing electricity from wind turbines and solar panels. I mean, batteries could play a role in easing us off fossil fuels. But key to all of that would be designing the batteries of the future with sustainability in mind. And Janelle is an environmental engineer by training. And when it comes to that metric, sustainability, lemons kind of have our double A's beat. You know, the lemon battery is non-toxic.

Right. Lemons are compostable, which we love. Because, you know, seriously, battery waste is a huge issue that we have to face. Yeah, we're not suggesting we build batteries out of lemons. But we are pointing out the virtues of lemons as we strive to create batteries for the future, right? Something made out of materials that are truly recyclable or reusable. and, like lemons, abundant. When we're thinking about, you know, new battery designs and new battery materials,

we want to choose materials that have abundance in nature and aren't a finite resource so that we can have a source for battery materials for a long time to come. I really like thinking about that. You know, all the years I've done this, I'm just so fixated on the kids getting the light bulb to glow. But, you know, it's good to think critically about the battery materials. part here and, you know, growing a giant lemon to power the planet. That was not the point of this episode at all. Well, girl can dream.

Okay. Today's episode was produced by Rebecca Ramirez, edited by Viet Le, and back-checked by Rasha or reading. Special thanks to Jay Sizz and Josh Newell, who were the audio engineers for this episode. And thanks also to Violet Thomas for getting us to look more deeply into batteries. I'm Maddie Safia. And I'm Emily Kwong. Thanks for listening to Shortwave, the Daily.

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