Temperature changes the state of water. At temperatures above 100 ํc it becomes water vapour or the gas, steam. At 0 ํc water freezes to from solid ice. Most solids becomes denser than their liquid from when they freeze but water is at its most dense at 4 ํc when it is still in a liquid from. Flowing water can be used to turn water wheels to provide power and in hydroelectric schemes is used to provide electricity. It circulates between the atmosphere and the Earth in a process know n asthe water, or hydrological, cycle.