Snow-making machines actually make tiny beads of ice, each one about one ten-thousandth of an inch in diameter.聽Water is sprayed from a hose together with compressed air.聽The air is needed because as it quickly expands, its temperature drops since it has to do work by pushing away air molecules.聽This cooling helps freeze the water.聽As the water freezes, it releases heat.聽This should be obvious when we realize that in order to melt ice, we have to add heat.聽The heat released is then taken up by the expanding compressed air.聽This is why the "snow-making" pipes are always high in the air.聽If the snow were made close to the ground, the heat released by the freezing process would actually warm up the ground and melt some of the snow.聽聽聽
The same principle is used by farmers who spray their crops with water when a freeze is in the forecast.聽It is a common聽misconception that the thin layer of ice produced acts as insulation.聽Not so.聽The freezing water liberates enough heat to keep the water inside the fruit from freezing.聽And聽why does skiing on artificial snow feel different?聽When skiing, pressure causes the snow to melt, increasing slipperiness.聽But the contact surface is not the same for real snowflakes and artificial ice beads and their temperature can also be different.聽 So, the rate at which they melt under pressure can be different.聽 Expert skiers will notice a difference, but those with meagre talents will only notice that it hurts more to fall on the artificial stuff.
