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You probably know that if you put an egg in a microwave, it explodes.
And you might know that if you put an egg in vinegar for a few days, it dissolves the hard outer shell,
and you're left with a squishy egg. It's called a naked egg.
The egg is still raw inside, but it's now got this kind of flexible, bouncy quality to it.
But what happens when you put one of these naked eggs in a microwave?
I had a theory before I start experimenting, which is this:
The reason a normal egg explodes in a microwave is because the water content of the egg starts to boil,
and that causes a buildup of pressure inside the egg. Eventually, the pressure gets to a point where
the structural integrity of that hard outer shell fails. You get a sudden release of pressure.
And that's why you have an explosion.
But if you have a buildup of pressure inside a naked egg, where the shell has been removed,
well, the membrane is stretchy. So maybe the egg will expand in the microwave.
So, the first step is to dissolve the shell of the egg. You normally do that with vinegar.
Soak it for a couple of days.
That's because it's a weak acid, so the acid is dissolving the shell.
See these bubbles, here? That's carbon dioxide forming.
But two problems with that: The first is it's boring, it takes ages. Let's speed it up with a stronger acid.
The second reason not to do it that way is, look, if you leave an egg just in its membrane soaking in liquid,
the egg will actually absorb liquid from around itself and expand.
The problem with that is, I want the egg to expand in the microwave. I don't want a pre-expanded egg.
Look at the size of this one. It's huge!
So we're gonna use 10M hydrochloric acid. It's really dangerous, don't try this at home.
This way, it takes about five minutes. Look at those bubbles!
That's interesting, isn't it. Why is it that the hard shell dissolves in acid while the soft, flexible membrane doesn't?
That seems counterintuitive.
Well, an acid has these ions floating around in it.
In the case of hydrochloric acid, it's negatively charged chlorine ions and positively charged hydrogen ions.
And, you probably know this, opposite charges attract,
so the negatively charged chlorine ions are attracted to the positive things.
And if you look at the chemical structure of an eggshell, it's calcium carbonate.
And calcium carbonate is an ionic crystal lattice.
That means it's made of positively charged calcium ions and negatively charged carbonate ions.
So, the negatively charged chlorine ions in the acid are attracted to the positively charged calcium ions.
And importantly, the calcium carbonate bonds are weak enough that the chlorine ion can steal the calcium ion,
forming a salt called calcium chloride.
Here's the full balanced equation.
Here's where the bubbles come from, that's carbon dioxide.
Now, in the case of the membrane, that's made of collagen.
Collagen is a large protein molecule, and the bonds within it are less polar.
And the links between the molecules are non-polar.
So there's not much to attract the positively charged and negatively charged ions in the acid.
And yet, the membrane of an egg does dissolve in our stomachs. In our stomach acid?
Is the acid in our stomachs just incredibly strong?
It's actually not the acid that dissolves the membrane of an egg in our stomach. It's enzymes.
An enzyme is a molecule that speeds up a chemical reaction.
In this case, it's an enzyme that clamps onto the protein, this long molecule, and just kind of snaps it in half.
Anyway, enough talk. Let's stick it in a microwave!
[bang!]
So there you go. Hypothesis proved right. A naked egg expands in a microwave.
Well, kind of. I'll get to that in a second.
One thing you do when you strip the shell off an egg, you have to do this.
You have to shine a torch through it, because you start to see some of the internal structure of a raw egg.
It's really nice.
One thing I noticed, look at this end, you've got this air sac. It's called an air cell, actually.
You've probably seen that if you eat a soft-boiled egg, if you break the egg at the round end instead of the pointy end.
I know that's controversial, but you'll see there's a cavity in there. That's the air cell.
And that's there for a reason.
When the egg first comes out of the chicken, there is no air cell, because the temperature inside the chicken is higher than the temperature outside the chicken.
What?! I know, it's true!
So here's what happens. When the egg is laid, it has to cool down.
And as the liquid inside the egg cools down, it contracts.
And when it does that, it draws air in through the air-permeable shell and it creates that little cell of air.
So, the air cell basically moderates the pressure inside the egg.
But back to that hypothesis, because actually, we got through about six eggs and we only got that expanding shot once.
Like, one of the eggs expanded a bit and then exploded, but the rest of them just didn't do anything and then exploded violently.
So, why is it that sometimes you get an expanding egg, sometimes you don't?
Here's the thing. And this is gonna sound like an excuse, but
in science, it's okay not to know everything. It's okay to be comfortable with ignorance.
In fact, it's ignorance that drives discovery.
What I would love to happen is to figure out the criteria to pretty much guarantee that a naked egg will expand in a microwave.
So I would love you guys to try this for yourselves, vary some things, see what you get.
I mean, we did different things. Like, maybe we soaked this one in acid for a little bit longer,
so maybe the acid was softening the membrane somewhat.
Maybe?
One of them we cooked a bit more slowly. We cooked it for a bit, then took a break, and then put it back in.
Who knows?
I did say "Don't try this at home" when I was talking about the strong acid.
What I mean is, only do this if you are a responsible adult. All right?
And you have to assess the risks for yourself before you start experimenting. There are many risks.
A quick announcement of sorts before I go.
My dad writes about science. He writes these really interesting articles about the nature of knowledge and how it relates to the scientific endeavor.
And the way he thinks is really interesting and really inspiring.
The problem is, if you want to read one of these articles, the only way to do it is to persuade him to email a Word document to you, which is like...no good, is it.
So we've been talking about putting the articles online, because I really want you to be able to read them.
There's a million different ways to build a website. We decided to go with Squarespace for a number of reasons.
And then after that, we got in touch with them, and they're sponsoring a few videos now.
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I'm just building the bare bones at the moment, like getting the template together and everything,
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We probably won't do that anytime soon.
Though, I could sell my books.
That's an option. I'll have to ask my dad.
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I hope you enjoyed this video. If you did, don't forget to hit "subscribe". I'll see you next time.