I’m thinking of like when you bottle wine that’s still fermenting, and it explodes. I understand that the fermentation process raises the air pressure inside the bottle. What I *don’t* understand is how? When you pump air into a balloon, the air pressure rises because there are *more* air molecules entering the balloon.
With wine in a bottle, you have a fixed amount of matter at a certain temperature. I don’t understand how fermentation could increase air pressure in a closed system?
In: Physics
Blow up a balloon. You just put maybe 5 grams of air into the balloon to make it that big.
Now fill the balloon with water. You put maybe 2000 grams of water to make it the same size.
Imagine how big the balloon would need to be to fit 2000 grams of air!
Gas takes up more space than liquid. As the matter inside the glass turns from liquid into gas, more space is required. The gas builds up, increasing the pressure until the glass breaks.
Gas takes up more volume than liquid. Fermentation is converting liquids into gas.
Similar concept- If you boil a sealed container the pressure will increase enough to be dangerous. The water turning into steam from it’s liquid form drastically increases the air pressure by converting liquid into gas.
Imagine you are inside a five cubic foot room. Inside this room with you is a two cubic foot box. Inside that box is a slightly smaller box, with a slightly smaller box inside that, and a smaller box inside that, etc.
You open the first box and take the smaller box out. Then you open that one and take the smaller box out. How long until you’re so smushed that you can’t move?
No additional matter entered the room, you just moved around the stuff that’s already there.
That’s basically how fermentation works. Sugars are pretty densely packed, and bacteria break those down into unpacked gasses. Those unpacked gasses begin to take up a bunch of space until there’s no more space to take up.
Fermentation induces chemical changes. You are right that the *same chemical* in a sealed container with no change in temperature will not change pressure, but different chemicals have different properties and fermentation changes the mix of what is in there such that the pressure increases. Basically the yeast poops out gasses that have much higher pressure than the sugar water of whatever variety that you started with.
Gas is bigger than whatever it was made out of.
There isn’t more matter/it isn’t heavier … But what is there takes up way more space.
(Steam takes up far more space than the equivalent weight of water.)
Think of a bullet. A bullet contains a modern version of black powder. Upon ignition it converts all the powder into gas, which propels the bullet forward really fast because the gas takes up way more room than the powder creating gas pressure. In the end it’s gas pressure that fires a bullet.
During fermentation basically the same process happens, just much slower. But the gas pressure will keep on rising as long as the fermentation runs.
So summarized gas (CO2) takes up WAY more space than the liquids and solids it’s made from.
Liquids and solids are much more compact than gasses, so if you replace liquid in a sealed container with gas of equal mass, The gas is going to want to spread out much more and will start pushing on the walls of the container trying to get out.
Think of it like how when you boil water, steam rushes out of the nearest opening because it no longer fits in the kettle. If you could somehow put some water in a balloon and boil it without breaking the balloon, the balloon would inflate despite having the same mass. Though it’s much easier to do that in reverse if you look up what happens to a balloon in liquid nitrogen or something.
Ever eat a bunch of cabbage and cheese and spend the night farting? You’re converting dense matter into gas, and potentially a lot of it. Bacteria do the same thing – eat a bunch of sugars and fart it out as gas. The air pressure increases because they convert the sugar (a big chain of carbon, oxygen, hydrogen atoms) and into co2 and alcohol (a smaller chain of carbon, oxygen, and hydrogen atoms). The total matter doesn’t change, but what was a big solid is now a smaller liquid plus a gas.
There’s an increase in *pressure*. CO2 is a gas so takes up a lot more space than it did as sugar. Vessels can only handle so much pressure before they explode.
The yeast is held together as a solid by chemical bonds. These bonds themselves are a form of energy, constantly countering any forces (such as gravity) that would try to spread out the yeast. You can have a pile of yeast that isn’t a puddle because it’s held together into granules by these bonds.
When a chain reaction occurs in the chemicals that starts destroying bonds, the bond energy is released and the byproducts are liquids and gasses (from what was once solids). This freed bond energy is now overloading and breaking the bonds of other solid yeast, and this goes on and on (this is why I called it a chain reaction).
So the glass breaks because the bond energy is no longer being used for bonding, and is now wild kinetic energy pushing randomly against the glass.
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This is also the simplified explanation for how your phone battery works. When you charge it you’re not adding new mass into the phone. When it depletes, it is no lighter than it was when it was charged. So how does it power your phone to perform computations and emit light?
It’s about the arrangements. Charging your phone is the act of reorganizing the inside of the battery to form lots of neat and tidy bonds between its atoms. Discharging your phone battery (eg into the screen’s light) is using the energy freed by breaking bonds.
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Now if you want an explanation of what bonds are that’s a different ELI5
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