Idea created from sparkling water
In: Physics
carbonated drinks have the CO2 in solution, meaning the CO2 is dissolved in the liquid.The air above the liquid when sealed is at equilibrium with the CO2 that is dissolved in the liquid. Another way of saying that there’s the same “partial pressure” of CO2 in the liquid as in the gas above the liquid so no CO2 comes out of the liquid to the gas.
when you open the bottle you release the extra pressure of mostly CO2, which lowers the partial pressure of CO2 significantly above the liquid. That lowering of pressure, especially CO2 partial pressure causes the liquid to have a higher partial pressure CO2. Things flow from high pressure to low pressure until they’re at equilibrium. So you get CO2 coming out of the solution in the form of gas bubbles.
IF you were to open a bottle of carbonated beverage and let it start to bubble, then close the bottle, you would notice that the bubbles stop forming, and after they all rise to the top and “pop” no more would form until you again open the bottle. Also, right after closing the bottle, squeeze it. it’s soft, meaning the pressure in the bottle is low. After the bubbles have all risen to the top and have popped, squeeze the bottle again. you’ll notice it’s stiff, indicating there’s more pressure in the bottle than before. That pressure came from the CO2 coming out of solution in the liquid (the bubbles) until equilibrium was reached.
The bubbles are carbon dioxide. When the bottle is closed there’s enough pressure that the carbon dioxide stays dissolved in the water, like sugar dissolved in hot tea, so you can’t see it.
When you open the bottle you release the pressure. The amount of carbon dioxide (or any gas) that will dissolve in water scales with pressure, so when you drop the pressure the water can’t hold as much carbon dioxide. The excess drops out of solution and forms bubbles, like when you cool sugar syrup and sugar crystals show up.
When you open the can and remove the pressure, the carbonation can escape the water. When trapped in the can or bottle, there isn’t enough room for the gas to escape.
When you heat a sealed container like this, the gas gains energy, and can *make* room to escape (by blowing the container apart).
(PV=nRT.)
The amount of gas that can dissolve in water depends on the pressure of the gas (each gas is dissolves separately if there is a mix). You can think about it in the same way that hot water can hold more salt or sugar than cold water can. Sitting on the shelf a carbonated bottle is pressurized to about three times normal atmospheric pressure and it’s all CO2. This is about 5000 times the normal pressure of CO2 in the atmosphere, so the liquid will have 5000 times more dissolved CO2 than a glass of water set out on the counter.
When you open the bottle, you depressurize it to normal atmospheric pressure and all that gas can’t stay in the liquid anymore and forms bubbles as it escapes.
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