Dozy, like most things chemical .... it depends.
I've spent a lifetime with Group 1 metals and showing their reaction with water to students.
If gum's pail is big enough and full of tap water at ambient temperature (say 10C and 1 or 2 gallons?) the whole event will be a non event. The Li will just effervesce. Yes I know about H2(g) ignition issues.
I would bet folding money that a pail of water with an iPhone battery would be a big enough thermal sink to keep the thermal runaway of the Li and the resultant kinetics under control.
But do wear full face protection and gloves. Li2O/LiOH in the eye, like that of any alkali, is properly serious
You have to push Li to get it to go "crack". Careful use of English.
If the temperature gets up, the rate of oxide formation on the metal substrate of Li2O (+Li2O2 for the pedants) will form a protective coating that eventually bursts with semi random explosive force/rapid combustion zones. For the record, you get crimson streamers radiating in parabolic curves from the point of release.
CW
Last edited by chris weston; 22nd January 2013 at 20:35.