Ask A Scientist Chemistry Archive

name         Katie R.
status       student
age          16

Question -   I have an assignment for year 11 chemistry asking me to
design an experiment to find how much the particles of a substance move
apart when it becomes a gas, I am to do this using a piece of dry ice. I
was wondering if you have any ideas on how to successfully catch this gas
as it is produced?
---------------------
Katie,

You might be able to generate the carbon dioxide in a closed system and then catch it 
in a balloon -- rather like placing an Alka Seltzer tab in a bottle, adding water, and 
then stretching the mouth of a balloon over the bottle top. However, do be aware, as 
the balloon expands, it will exert a compressive force on the gas inside. Thus, the 
molecules will be squeezed closer to each other. This may interfere with your 
experiment.

Regards,
ProfHoff 852
=====================================================
Balloons, plastic baggies, and upside-down water containers full of water, sitting in a 
bigger bucket of water so they cannot spill,
 are the most common things for catching gasses.

I guess you have to be a little careful that the extreme cold of your chunk of dry ice 
does not make the envelope develop a puncture.
That leaves out balloons, probably.

Polyethylene is not too sensitive to cold, so gallon-sized polyethylene bags with a zip-
lock might work.
Scotch-tape a bit of paper towel around a tiny chunk of dry ice, throw it in the bag, 
squeeze out as much air as you can, and seal the zip-lock.
Then wait till the ice is gone, and the bag stops expanding.  I wonder if you really 
need the paper towel.

Slippery things take a little trial and error to catch.

Jim Swenson
=====================================================