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Thinking Out Loud: Soda Pop

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Okay, science peeps, help me out. I want to do a gas laws lab, and this xkcd strip got me thinking about the 2.2 grams of CO2. It isn’t cited, as Mr. Munroe is usually so careful to do, so I don’t know where it comes from. I want to know how much CO2 is in a can of pop.

Here’s the train of thought:

Part I:
I’m thinking we can use Boyle’s Law (P1V1 = P2V2) to find the pressure inside the can. Open can, catch all gas, fill space in can with water.
P1Vfill-defizzed-pop-can-with-water = PatmosphereVcatch-escaping-gas-somehow-measure-it

Part II:
Take newly generated P and calculated V, use with Ideal Gas Law:
PcalcVinside-can = (n)(R)Tmeasured

How is this idea? Is it double-dipping on data? Doable? Feedback, please!

Sources of error will probably be fun, but I’m okay with students finding those.

Wonder if we’ll get something close to 2 grams.

Could compare can to plastic bottle, different kinds of pop…


4 responses »

  1. Sounds like it could work, and I would be interested to see what you got! I think the biggest hurdle will be figuring out how to capture the gas… on that tangent, I feel like a plastic bottle may be easier to handle in that you could potentially unscrew the cap with a balloon already over the top to minimize the amount of CO2 loss

    • Thanks.

      I think I’m going to try this and another method (or two?) after spring break… can always use some comparison/contrast of methods stuff.

  2. William Bartrug

    I just stumbled across your blog, because I am doing a PBL on gas laws right now doing this very thing. I’m learning as I go, but I have found awesome data using test tubes. You fill large test tubes with a set amount of soda (I used 20mL), use a double-holed stopper, and use data probes (temperature and pressure) to gather data. I’m also going to try using a syringe to measure change in volume. If you have any more luck, let me know!

    • My students opted to just mass a can, open it and let it go flat over the weekend, and mass again. Pretty close to 2 grams.

      Am still hoping one of them takes me up on this lab, but am now less optimistic.

      Let me know how yours works out!


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