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Experiment air1:
Air has a mass
(Attention: Hydrochloric acid is corrosive)


"A substance is something that has a mass and a volume." Demonstrate that air has a volume by replacing air by another gas on a balanced scale.

* Left photo: Balance two "empty" clean Cola
   cans on a scale. The right one is closed by a sticky tape.
* Generate hydrogen from a piece of zinc and 20 ml of hydrochloric acid (10%) in a 50-ml vial
   closed by a stopper which is punctured by a drinking straw.
*  Take the right Cola can from the scale and put its opening over the straw to replace the air
    by hydrogen (H2).
* Right photo: The can with hydrogen -closed by sticky tape-  placed bottom up on the
   right pan has lost weight:  1/3 g gram has to be added to the right pan to rebalance the loss of 330 ml air.
   (The weight of H2 may be neglected).


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