Why does snow look white but water is colorless?

Snow is a block of individual ice crystals arranged together. When a light photon enters a layer of snow, it goes through an ice crystal on the top, which changes its direction slightly and sends it on to a new ice crystal, which does the same thing. Basically, all the crystals bounce the light all around, so that it comes right back out of the snow pile. It does the same thing to all the different light frequencies, so all colors of light are bounced back out. The ‘color’ of all the frequencies in the visible spectrum combined in equal measure is white, so this is the color we see in snow.