Water is a transparent, tasteless, odorless, and nearly colorless chemical substance that is the main constituent of Earth's streams, lakes, and oceans, and the fluids of most living organisms. It is vital for all known forms of life, even though it provides no calories or organic nutrients. Its chemical formula is H2O, meaning that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. Water is a liquid at standard ambient temperature and pressure, but it often co-exists on Earth with its solid state, ice, and gaseous state, water vapor or steam.
Water plays many important roles in nature and in human life. It acts as a solvent, dissolving many substances and facilitating chemical reactions. It is also the primary medium in which living cells perform their functions. In addition, water is an essential component of the Earth's hydrological cycle, which involves the movement of water between the Earth's surface, the atmosphere, and the subsurface. Water is also a vital resource for agriculture, industry, and domestic use, and it is used in a variety of recreational activities.
Water is a polar molecule, meaning that it has a positive charge at one end and a negative charge at the other end. This property allows water to dissolve many ions and polar molecules, making it an excellent solvent.
Water has a high heat capacity, meaning that it can absorb or release a large amount of heat without changing temperature. This property makes it useful for regulating temperature in living organisms and in various industrial processes.
Water is also a good conductor of electricity, although not as good as some other substances such as metals. This property is due to the presence of ions in water, which can carry electrical charges.
Water has a high surface tension, meaning that it tends to resist breaking apart at the surface. This property is due to the cohesive forces between water molecules, which cause them to stick together.
Water also has a high boiling point and a low freezing point, compared to other substances with similar molecular weights. This is due to the strong hydrogen bonds between water molecules, which require a lot of energy to break.
Water is also a dense liquid, meaning that it has a high mass per unit of volume. This property is due to the close packing of water molecules, which results in a high density.
Water density is the mass of a given volume of water. Water has a density of approximately 1 gram per milliliter (g/mL) at standard temperature and pressure (STP). This means that a liter of water, which is equivalent to 1000 milliliters, has a mass of about 1000 grams.
Water density varies slightly with temperature. At 4 degrees Celsius, the density of water is at its maximum, with a value of approximately 1.0000 g/mL. As the temperature increases, the density of water decreases, reaching a minimum value of 0.9982 g/mL at approximately 39 degrees Celsius. Above this temperature, the density of water increases again.
The density of water is also affected by the presence of dissolved substances. When a substance is dissolved in water, it can increase or decrease the density of the water depending on the substance and the concentration of the solution.
The density of water is an important property because it affects the buoyancy of objects in water. An object that is less dense than water will float, while an object that is more dense than water will sink. This property is used in many practical applications, such as in the design of ships and submarines.