Why does a coke can's weight change when opened?

[Himal kharel]

when a can of coke placed in a sensitive balance is opened what happens to the reading?
the answer of this question is given first increases and decreases.
can anyone explain this?

 

[darkxponent]

can coke opens and liquid bursts out of it with some acceleration which means: can applies force on liquid which means: liquid applies force on can::

so net force on can increase so does reading

now when the liquid is completely out the mass of can is reduced and so does reading

 

[sophiecentaur]

In a less dramatic scenario, the CO2 gas is escaping from the hole in the top and this pressure is causing an increase in downward force. Once the fizzing has stopped and there is less CO2 in there, the final weight will be less (and there may be some water evaporation too.
Should I be doing all this thinking for you? Is this a h/w question?