Why Does Ice Float?
Ice is a solid. When the temperature is cold enough, liquid water be- comes solid ice. Water expands greatly when it freezes. Ten litres of water make about 11 litres of solid ice.
Objects in water float or sink according to a principle that was first discovered by Archimedes, a Greek mathematician who lived in the third century B.C. This law, known as ” Archimedes’ Principle”, states that any object placed in the liquid is buoyed up or held up by a force equal to the weight of the liquid displaced.
Wood is one-half as heavy as water, therefore one-half its volume of water will hold it up. Cork is one-fifth as heavy as water. Ice is about nine-tenths as heavy. This is why about nine-tenths of an iceberg is under water and an iceberg may really be much larger than we think it is when we see it.
Ice near the freezing point may be melted by adding pressure, but it refreezes quickly when the pressure is released. When you squeeze a snowball, you melt some of the ice crystals hut they freeze again to make a hard ball when you stop squeezing.
Because water expands greatly when it freezes, a great force is put forth when ice is formed. Rocks are often split by water freezing in tiny cracks or crevices. This is important in the slow breaking down of mountains. In fact, in the quarries of Finland, workmen split great blocks of rock by filling cracks in the rock with water and allowing it to freeze.