Ice. It comes in a wondrous variety of forms. Take a close look outside on a cold winter day and you’ll be amazed at the variety, from lake ice hard enough to drive on to dirt-encrusted drifts. There’s powder for skiing and packed snow for sledding and snowballs. Greasy curbside snow comes from salting and sanding the roads. And, there’s even man-made snow on ski slopes – do you know what they use to make that?