In order for ice skates to work properly, they have to be able to slip and glide over the
ice with as little friction as possible. Most people think that it's the ice that's slippery, but the truth is, ice by itself is no more slippery than a smooth concrete sidewalk! The thing that makes a skate slide is a thin film of water underneath the blade. As it turns out, when you glide over the ice, the heat generated by the blade of the skate rubbing against the ice causes some of the ice right under the blade to melt. This water acts like a lubricant under the skate, reducing friction and making it slide. As soon as the blade passes by, the water re-freezes to ice, so that's why you don't usually see it!