These properties of water are all a result of hydrogen bonding. Hydrogen bonds result from the electrical attraction between partially positive hydrogen atoms and partially negative oxygen atoms of adjacent water molecules. The differences in electronegativity between hydrogen and oxygen give rise to the hydrogen bonding and associated properties.

Attraction and polarity in water molecules cause them to "stick" to one another. Attraction between water molecules results in cohesion, and attraction between the water molecules and other compounds in the environment results in adhesion. The high surface tension of water is caused by the "sticking" of water molecules to one another, which keep vapor pressure low.

Hydrogen bonding is a temporary intermolecular force, and is different from covalent or ionic bonding. Covalent and ionic bonding result in permanently joined atoms to build molecular structures.

Water, unlike many other compounds, has several special properties due to its hydrogen bonding between molecules. The hydrogen bonds are relatively strong, leading water to have very low vapor pressure and high surface tension. A side effect of the hydrogen bonding, however, is that when water crystallizes, the molecules will inevitably align so that the hydrogen bonds are maintained. The solid lattice structure of water molecules is, thus, not very tightly packed. The structure is ideal to optimize intermolecular forces, rather than space and volume. The density of the solid (ice) is thus less than the density of the liquid water.

Water vapor (gas) and supercritical water both have lower densities than ice, making liquid water the most dense.

Adhesion refers to the attraction between water molecules and foreign particles or surfaces. Cohesion refers to the attraction between one water molecule and another.

Adhesion of water to the cell walls of the xylem vessels and cohesion of water molecules to one another allow for water transport in plants. This is also known as capillary action.

The high heat capacity, low solid density, and polarity of water, as well as its use as a solvent, are all essential to the role of water in supporting life in other ways.

Iron is important for many organisms but it isn't found in quantities large enough for it to be a major component. It is part of the trace minerals. Carbon, nitrogen, sulfur and oxygen are all part of the bulk elements, elements that are found in the largest quantities (they make up 96% of organisms).

Nonpolar compounds will not be adequately dissolved in aqueous solutions. Lipids are nonpolar compounds that are mainly insoluble in water. This causes lipids to congregate together, rather than be broken apart in aqueous solutions. Lipids will generally come together to form globs or balls called micelles.

Ions, amino acids, and sugars (carbohydrates) are all polar, and will be adequately dissolved and ionized by water.

Catabolism means to break something down, usually from a larger starting point to one or more smaller byproducts. Hydrolysis is the most common reaction in the human body. Hydrolysis means "breaking" through the addition of a water molecule. You will see hydrolysis as an important reaction in many pathways in the human body.

A hypertonic solution has a higher concentration of solute than the solute in the cell. Water diffuses to the higher concentration of solute, so water diffuses out of the cell, and the cell shrivels up. One way to think of this is that water follows "salt," as salt is the most common biological solute.

When there is a concentration gradient, water will move across a membrane unassisted by ATP or channel proteins. In contrast, solutes (the dissolved substances) cannot cross the membrane unassisted.

Water is a polar molecule because the bonds between oxygen and hydrogen are polar covalent bonds. This means that although they form covalent bonds (normally non-polar) the difference in electronegativity is great enough to make one side more negative (oxygen side) and the other side more positive (hydrogen side). However, the polarity isn't as strong as the polarity in ionic bonds so we donate the charges with the greek letter delta to show that they are partial charges.

Acidic compounds and solutions release hydrogen () ions. Basic compounds and solutions release ions and take up hydrogen ions. Because of their charge acidic compounds and solutions do not mix well with oil, which is nonpolar.