Identify the phase transition occurring in each of the following.
a. Mothballs slowly become smaller and eventually disappear.
b. Rubbing alcohol spilled on the palm of the hand feels cool as the volume of liquid decreases.
c. A black deposit of tungsten metal collects on the inside of a lightbulb whose filament is tungsten metal.
d. Raindrops hit a cold metal surface, which becomes covered with ice.
e. Candle wax turns to liquid under the heat of the candle flame.