At room temperature, pure water is a colorless, tasteless, and odorless liquid. When viewed through considerable depths, it has a bluish tint. Water is one of the most plentiful and essential of compounds. Until the 1780s, it was regarded as a basic element typifying all liquid substances. Scientists did not discard that view until British chemist Henry Cavendish synthesized water by detonating a mixture of hydrogen and air.
Although its chemical composition is simple, its chemical properties are complicated and unusual. Compared to analogous compounds, such as hydrogen sulfide and ammonia, its melting and boiling points are much higher than would be expected. In its solid form, ice, water is less dense than when it is a liquid. This is caused by the unique structure of the water molecule. In an ice crystal, the association of the molecules is highly ordered but loosely structured. When the ice melts, this orderly arrangement breaks down and the molecules pack more closely together, making the liquid denser than the solid.
Water is the major constituent of living matter, accounting for as much as 90 percent of the weight of living organisms. Protoplasm is primarily a solution of water containing fats, carbohydrates, proteins, salts, and similar chemicals. Water acts as a solvent for these substances and also plays a significant role, through the process of hydrolysis, in the metabolic breakdown of essential molecules such as proteins and carbohydrates.