text: The "white" is caused because snow has a great many tiny interfaces, called "phase boundaries," where air (a gas phase) meets ice (a solid phase).  Every time light encounters a phase transition, it is defracted.  If you've ever looked at a stick submerged partially, you've seen this--a straight stick will look like it has a bend in it right at the water's surface.  Well, with snow, the tiny ice crystals, and the many small bubbles in ice (water is a bent and polar molecule, so when it freezes, it expands, making small bubbles inside), and the places where individual ice crystals begin and end--all of this scatters light all around.  This makes it so that a big bunch of snow will look white.  If you look at a single snowflake under a microscope, though, you will see that the crystals individally are clear.\n\nWhen it melts, there is only one phase transition, right at the surface.  The light is defracted a bit, but only once--it doesn't scatter light all around like snow does.\n\nBut it can!  If you've ever seen a big fountain, where the water is splashing and tumbling about, it will also look white due to phase transition.  Likewise, if you make a whole bunch of tiny bubbles under water, you can scatter light and make it look white.