Water is a natural occurring substance that contains two atoms of hydrogen and one atom of oxygen, held together by covalent bonds. It exists in gaseous, solid, and liquid states and has several distinctive properties; it is a universal solvent, it is cohesive, and it is adhesive. It also has surface tension, polarity, electrical conductivity, and a neutral pH.
Water as the Universal Solvent
A solvent is a substance that is capable of dissolving other chemical compounds. Water is called the universal solvent because it can dissolve more substances than any other common liquid. For example, water can break salts into their component ions, hydrate the ions, and prevent them from interacting.
Most chemical elements have high solubility in water, meaning that a large amount of the element can build up in the water before the water molecules' capacity to isolate additional ions has been met. When there are no more water molecules available to isolate a substance's ions, the mixture has reached the point of "saturation." At the point of saturation, the mixture begins to form solid precipitates.
Water has polarity, which means that the charges on each end of the molecule are not equal to one another. These unequal charges are caused by an unequal distribution of negatively charged electrons. Electrons are unequally distributed across the water molecule because the oxygen portion of the molecule attracts more electrons than the hydrogen portion. Therefore, the side of the molecule with the oxygen atom is more negative than the charge on the side with the hydrogen atoms; this causes the water to have several strange properties, including high surface tension.
Water is both adhesive and cohesive. Adhesion is a force that holds the molecules of a liquid to other surfaces. This occurs in water because water molecules have polarity; the positive end of each molecule can form a bond with negatively charged surfaces. Cohesion, on the other hand, is a force that holds molecules of a liquid to other molecules of the same liquid. This occurs in water because the positive side of each water molecule can bind to the negative side of another molecule.
Water Properties: This is a page that discusses certain properties of water, including adhesion and cohesion.
Surface tension occurs when a liquid's surface is in contact with a gas and forms a thin sheet that is harder to penetrate than the liquid beneath it. Water possesses this property because cohesive forces are pulling its molecules in every direction except upward. This creates a skin-like surface on the water. It is this property that allows certain objects, such as paperclips, to float on water.
Electrical conductivity is a measure of the ability of a substance to conduct an electric current. The more ions a substance has dissolved, the higher its electrical conductivity; because water is the universal solvent, it is considered a good conductor of electricity. Water that has a higher concentration of salt ions is usually a better conductor than water with a lower concentration of salt ions.
Conductivity: This page explains electrical conductivity and describes its connection to water.
PH is a measure of how acidic or basic a substance is. Possible pH values range from zero to 14, with 0 being the most acidic and 14 being the most basic. The pH of water is typically around 7, this means that water's pH is neutral and it is neither acidic nor basic.
Water Chemistry: This is an article that includes information about many of water's properties, including pH.