Question about carbonation

[clifffaith]

Off the wall question. Coming home from the grocery store Tuesday we heard the bag with four big plastic bottles of Diet Cherry Pepsi fall over in the trunk. No biggie, plastic bottles. Fifteen minutes later we are at our front door and liquid is leaking out of the reusable grocery bag. Quick step in the door, kitchen is right there, place bag in sink. Wiped down each bottle, and only by lining them up can I see that one appears to be maybe 1/4” less full than the others. Closer inspection shows the twist top on that bottle was partially twisted. Fine, I’ll open this bottle first.

Why is it that this bottle is completely flat, not only that day which I expected, but forever and always? Why does spewing 1/8 cup, or less, of liquid, take ALL the carbonation away when the bottle tips? We have also noticed if we travel to a higher elevation with a 1/2 to 3/4 full bottle of pop, that the bottle is mostly flat upon arrival.

 

[Sandy VDH]

Pressure keeps bubbles in liquid and in suspension, releasing the pressure too quickly and the bubbles come out of solution fast. However once the lid is off the bottle there is not way to get the solution under pressure again. Unless you own a sofa stream, and can add carbination back.

Same principles of Scuba diving. Which is why you need to gas off at a safe pressure, and it is why you should NOT rapidly ascend, which releases the pressure to quickly and thus causes bubbles to form in the blood stream. Which is why if you have the bends from diving they put you in a pressure chamber and pressure up the system to force the bubbles back into the liquid (blood) and slowing bring down the pressure.

 

[DaveNV]

Release the pressure inside the bottle, and the CO2 leaks out before any liquid drains. (Think of a balloon with a tiny hole in it.) The CO2 is where the bubbles come from. No CO2, no bubbles. No bubbles = flat soda.

Dave

 

[T_R_Oglodyte]

Why does spewing 1/8 cup, or less, of liquid, take ALL the carbonation away when the bottle tips?

It's not the loss of liquid; it's that the bottle lost its seal. As soon as the bottle lost it's seal, CO2 started leaking out. Amplified by the fact that the bottle tipped over; that encourages even more CO2 to come out of solution when opened. (Think of the old trick where you shake a can of soda vigorously before handing to to someone to drink; they pop the top and get spewed upon.)

And as other have noted, once you've lost the carbonation, the bottle will always taste flat because the contents have been decarbonated.

 

[sue1947]

Plus, plastic bottles will also leak out pressure/carbonation. If that bottle had been sitting on the shelf for a long time, it might have been flat when you bought it.

 

[DaveNV]

Plus, plastic bottles will also leak out pressure/carbonation. If that bottle had been sitting on the shelf for a long time, it might have been flat when you bought it.

Especially if someone cracked the seal in the store, as apparently happened, based on the cap being partially opened. it seems unlikely the cap would open itself just by falling over in the car.. The CO2 may have been gone a long time beforehand. I suspect the bottle had been opened previously, and wasn't properly sealed when they bought it.

Dave

 

[T_R_Oglodyte]

Especially if someone cracked the seal in the store, as apparently happened, based on the cap being partially opened. it seems unlikely the cap would open itself just by falling over in the car.. The CO2 may have been gone a long time beforehand. I suspect the bottle had been opened previously, and wasn't properly sealed when they bought it.

Dave

Very true.

 

[Patri]

A science question for us oldies! And they came through.

 

[clifffaith]

Especially if someone cracked the seal in the store, as apparently happened, based on the cap being partially opened. it seems unlikely the cap would open itself just by falling over in the car.. The CO2 may have been gone a long time beforehand. I suspect the bottle had been opened previously, and wasn't properly sealed when they bought it.

Dave

Twist tops have multiple “points” where the cap attaches to the “ring” around the neck (the ring that stays on the bottle when the cap is removed). When you twist open slowly the “points” break one by one. When I inspected the bottle I could see that the cap had twisted enough to break 2-3 “points” allowing liquid to spew. I could see a sliver of clear bottle neck behind the gray cap in one spot. I had to crack the remaining points on the seal to open the bottle, so it hadn’t been previously opened.