It is the positive area around the hydrogen that attracts the negative region nearer the oxygen atom. For that reason, this type of bonding is called hydrogen bonding. In summary, a hydrogen bond is a weak electrostatic force caused ultimately by the low electronegativity of hydrogen.
It is the hydrogen bonding of water that creates many of its properties - properties needed for life on Earth. The cohesion of water - its ability to stick to itself - is necessary for water to move up and out of a plant. The hydrogen bonding of water makes it resist temperature change better than most liquids and enables water to remain a liquid over a wide temperature range. It is the hydrogen bonding of water that enables water to dissolve many polar substances, hence our reference to water as the "universal solvent".
Solutions.
A solution is a homogeneous liquid mixture of two or more substances. The substance in the greater (greatest) quantity is called the solvent and the other component(s) is (are) called the solute(s). When water is the solvent, the solution is called an aqueous solution.
In an aqueous solution, most of the water is in its molecular form, H2O. However, a small amount of the water will dissociate into ions - one hydrogen ion (H+) and one hydroxide ion (OH-) per molecule dissociated. The pH scale is used to measure the concentration of hydrogen ion in an aqueous solution. With pH measurements, the letter p indicates negative log and H indicates hydrogen ion concentration. So pH means the negative log of the hydrogen ion concentration. Thus higher pH readings indicate less hydrogen ion. Lower pH readings indicate more hydrogen ion.
Acids and Bases.
An acid is defined as any compound that donates hydrogen ion (H+) to a solution. A base (an alkali) is defined as any compound that accepts hydrogen ion and removes it from solution. The more acidic a solution is, the higher its concentration of H+.
