 Hi, welcome to The Mix, the teen center at the San Francisco Public Library. My name is Eliana and I am your humble host for our STEM Challenge Yourself series, where our fabulous librarians will bring science experiments using household items that you can do at home. In today's challenge, you are going to learn how to mix different ingredients and bounce a raw egg. I think you're up for it. Ready? Hi everyone, my name is Davey. I'm a librarian here at the San Francisco Public Library. Today's question is what happens when we take away an egg's shell? Well, I'm going to show you what happens. We're going to make a rubber egg. So first things first, egg shells have some things on them that can be bad for our health. So make sure anytime you're handling raw eggs that you wash your hands after. If you don't feel comfortable using a raw egg for this experiment, you can hard boil the egg first and it will still work. All right, so here's an egg. Eggs have a hard outer shell. They also have a membrane underneath. The membrane and the shell hold in the yolk and the egg white and there's also an air pocket. Now the shell is made from a mineral called calcium carbonate. We're going to break this material down and dissolve it away. So let's get started. I have a pint-sized jar right here. All right, you just need something deep enough that you can completely submerge the egg. Next, we need an egg. All right, eggs have a habit of breaking. So consider using a couple of eggs in this experiment. I recommend not stacking the eggs. That makes it a little harder for the shells to dissolve. All right, you can use brown or white eggs in this experiment. It doesn't matter, both works. Next, we're going to need something to dissolve away the shell. I'm going to use a common household acid right here, white vinegar. Acids and bases are chemicals that react when they come in contact with each other. So we're hoping the acid from the vinegar will break down the base and the shell. Finally, if you want a little splash of color in your life, you can add some food coloring to your mix to see if it gets into the egg. All right, so let's set up our experiment. First, we're going to take our egg and we're going to carefully place it into our jar. All right, be very careful so you don't crack the egg. Next, we're going to pour the vinegar over the egg until it's completely submerged. Now it's okay if your egg floats a little bit at this point. Just make sure to turn it if it keeps floating. All right, and now we get to the hard part of the experiment. We wait. We're going to sit here for 24 to 48 hours at least. All right, you have to let your egg soak at least 24 to 48 hours. If you want it to go a little faster, you can try changing out the vinegar after about 12 hours and that could accelerate the process. All right, you actually can keep it even longer if you want. My eggs here, I have one that I've been soaking for about four days and another that I've been soaking for about seven. All right, but 48 hours is going to be your minimum. All right, so let's take a look. I just poured the vinegar and I can already see a reaction on my egg. Yeah, what's going on here? Tiny little bubbles are floating up to the surface. That's a pretty cool reaction. I like that it started all ready. Well, this reaction here is called an acid-base reaction. All right, acids are chemicals that taste sour and they can include things like citrus acid, vinegar, even the acids in our stomach could be counted. All right, this acid in white vinegar is called acetic acid. Egg shells, on the other hand, get their hardness from a mineral called calcium carbonate. All right, a common base substance found in other things like rocks, snail shells, and even pearls. Base chemicals can have a bitter taste to them and they often feel slippery. All right, and they include things like soaps and baking soda. So when we submerge our egg in the vinegar right here, the acid in the vinegar reacts with the calcium carbonate in the shell causing it to break down. This reaction creates carbon dioxide, which are the bubbles forming on the outside of our shell. Now over the next 24 to 48 hours, the shell is going to dissolve away and it's going to create kind of a gross-looking foam on the top. All right, this is the difference between using a white egg and a brown egg is what color foam you want to be cleaning off of your egg in the egg. All right, after about 48 hours, we can take our egg and we can carefully clean it. All right, so like I said, I have an egg here that I have been soaking for several days and we are going to go ahead and see what happens when we remove it. All right, so I'm going to carefully, carefully, carefully remove it from my jar. Normally, I would rinse this off in the sink very carefully, but I want you all to see what's going on so I am going to rinse it in this tub of water. All right, congratulations. We now have our very own rubber egg. All right, I'm going to dump this water so we can play around in this container and see what happens. Do we think we can bounce it? Let's find out. I'm just going to start bouncing it, you know, just a couple inches. Didn't break. Very nice. Let's try it again. Let's try it from about a foot. Let's see if it'll break then. Ooh, cool. We got it to break. So that one couldn't bounce very far. This shows me how careful we have to be. All right, so how did your egg feel? Now that the shell is completely dissolved away. It should be pretty rubbery. All right. So while the acid in the vinegar went ahead and dissolved away, all of the eggs shell, it actually also reacted with the proteins in the membrane, which made it rubbery. So the longer you soak your egg, the more rubbery it's going to become. And actually, you'll notice your rubber egg might look a little bigger. Well, that's because the egg's membrane without the hard shell allowed some extra water into the egg, causing it to swell. This is called osmosis. Now, I love this experiment because I get to use all of my senses. I get to smell the acid and the vinegar. I get to watch the shell dissolve and turn into bubbles and foam. And I get to feel a bouncy rubber egg. But the experiment doesn't have to be over now. You can play with your rubber egg. See how far you can get it to bounce. You'll notice I get mine to bounce after six inches, but after 12 inches, it popped. You think you can get yours to fall even farther? And now that the egg doesn't have a shell anymore, you think we can get things to flow through the membrane. Try submerging your egg in other things. Water, orange syrup, salt water, and see what happens. The possibilities are endless. Back to you, Yana. Thanks, Davie. What an interesting way to think about what you can do when you mix eggs and anything else. I think I can't look at eggs the same way. If you want more information about this STEM challenge and other STEM challenges, be sure to visit sfpl.org slash STEM challenge. Keep experimenting and stay STEM-tastic.