a more common liquid, that has some of glasses properties, is silly putty!
it is more liquid, but if you give it a sharp snap, it pops, and breaks "clean". think about? does liquid water ever snap and break clean? no! there are lots of others liquids that behave "unliquid-y"!
trouble is, your son thinks all liquids follow the "general rules" for liquids..(ie the rules first noted by Newton, i.e., liquids flow, (they don't hold there shape) they take the shape of what ever contains them, there viscosity is effected by tempature (actually this is true of glass at high heat, but not at "room temperature", and so on.)
for example... think what would happen if you put an electric mixer (turned on!)into a full bowl of water-- a shower! (a common liquid, acting as we (and Newton!) expect.
but take an other liquid (here you have a choice-- egg whites, or STP motor oil treatment!) turn the mixer on, put them in the bowl.. and no shower.. in fact, rather than being flung away (as water and most liquids would be) egg white and STP cling to the beaters! (that why STP works in your engine, the actions of the engine actualy attract the STP, and increase the lubrication effect!)
Glass is not a common liquid, and it doesn't obey the general rules. but "non-newtonian" fluids are fairly common.. send me a PM for more interesting "kitchen science" experiments!
