Water is polar for all of these reasons. First, oxygen is more electronegative than hydrogen. This means that oxygen attracts electrons more strongly than hydrogen does. Thus, in the hydrogen-oxygen bond of water, the electrons will be distributed asymmetrically--they will be oriented more towards oxygen than hydrogen. The molecular geometry of the water molecule (bent) results from oxygen containing a steric number of four with two lone pairs, thus the molecule has a slightly positive end and a slightly negative end.

An amphipathic molecule is one which contains both hydrophilic and hydrophobic regions. Benzene is made up of six carbon atoms joined together in a ring, with one hydrogen atom attached to each carbon (). This makes it a hydrocarbon, meaning that benzene is entirely hydrophobic. It does not have any hydrophilic regions and thus cannot be amphipathic.

Calcium chloride () is an ionic compound. This means that it is hydrophilic, not amphipathic. Acetic acid () is an interesting compound because it consists of a methyl group and a carboxylic acid. The carboxylic acid is hydrophilic. The methyl group, consisting of a carbon and three hydrogen atoms, is hydrophobic, but this group is too small to make the entire compound amphipathic. Thus, acetic acid is not amphipathic.

Lastly, palmitic acid () is definitely an amphipathic molecule. The carboxylic acid portion is hydrophilic, and the hydrocarbon chain is very long, making up the hydrophobic region.

Because of hydrogen bonding, water has a low high heat of vaporization. In other words, it takes more energy to free up water molecules from a hydrogen-bonded liquid state to a gaseous state.

Interstitial water is the fluid on the outside of cells, and surrounds the cells of the human body. While estimates vary, the best answer is that 15% of the entire human body is composed of interstitial water. Overall, about 60% of the body (42L) is composed of water. Additionally, about two-thirds of the total body water is intracellular water. Finally, about 5% of the entire body is composed of plasma.

Remember that these percentages are estimates, and vary by individual. Sex and muscle mass are two factors that can significantly alter these estimates.

Oxygen is a more electronegative atom than hydrogen, and therefore attracts electrons within the molecule more strongly than hydrogen. Because electrons are negatively charged, oxygen must therefore contain a partial negative charge, while hydrogen must contain a partial positive charge.

Because water is neutral, the overall charge should add up to 0. However, there are two hydrogens in water, compared to one oxygen. Two positive charges of  will cancel out a single negative charge of .

Hydrogen bonding occurs when a hydrogen atom covalently bonded to an fluorine, oxygen, or nitrogen interacts with a lone pair of electrons on another fluorine, oxygen, or nitrogen atom. So first, the two hydrogens in water can form hydrogen bonds, as they are connected to an oxygen atom. Next, the oxygen atom in water has two lone pairs of electrons, and those also can form hydrogen bonds. A single water molecule therefore has the capability of forming four hydrogen bonds.