If you put a lump of solid carbon dioxide (dry ice) in a paper cup or
on a paper plate on the kitchen counter, it gets smaller and smaller
and finally it just disappears, but you never see a puddle around it
like you would with regular ice!
Carbon dioxide has no liquid phase when the pressure on it is less than
about 5 times normal atmospheric pressure. So in the kind of pressure
that we like to live in, dry ice goes straight to gas when it melts. That kind
of behavior is called "sublimation", and we say that the dry ice "sublimes".
Every substance has some pressure limit like that. For water, it's 0.006 of
normal atmospheric pressure. At any pressure lower than that, liquid water
can't exist, and an ice cube sublimes ... it melts directly into water vapor
without a puddle.