Water's atomic structure is incredibly simple. Two hydrogen atoms are linked to one oxygen atom in this arrangement (Figure 4.1). Water molecules have unique electrochemical characteristics due to the nature of their atomic structure. It is because of this that water is able to dissolve other substances and act as a solvent for many compounds including salts, sugars, and proteins.
There are several properties of water that make them interesting from a chemistry perspective. First of all, water is the most common molecule in the universe after hydrogen gas. It can form strong bonds with other elements including carbon, nitrogen, phosphorus, sulfur, and oxygen. These interactions are usually very stable so water can be used as a solvent to extract these elements from their natural state or they can be incorporated into water-based solutions or liquids.
Secondly, water is important because it can participate in many different reactions. This makes water a valuable reagent in laboratory experiments because it can react with many substances simultaneously, sometimes in surprising ways. For example, when sodium hydroxide (a base) is mixed with hydrochloric acid (an acid), water is produced as a byproduct. However, if the mixture is heated, the hydrogen chloride gas released by the hydrochloric acid will combine with the water to produce chlorine gas which is an inert gas.
Water's distinct qualities are due to the polarity of its molecules, especially its capacity to form hydrogen bonds with one another and with other molecules. We'll look at how hydrogen bonding works in more detail later. For now, it's enough to know that the hydrogens in each water molecule are free to share their electrons with other molecules, but they only do so with those whose surfaces are electrically charged (+1 or -1). The result is a strong attraction between opposite charges and repulsion between like charges.
This bond energy is what gives water its unique properties. It allows water to be a solvent for itself as well as most other substances. A substance is called "soluble" in water if there is a stable interaction between the two. If the bond energy is too weak, the substance will simply float around inside the water; if it's too strong, the substance will not be able to enter the water at all. Most chemicals have solubilities near 100 percent in water, which means that they can be dissolved into the liquid and then separated out again by simple filtration or centrifugation.
The high degree of solubility of many chemicals in water helps to make it a useful solvent for washing away impurities from materials such as cloth, metal, and glass. Water also has some use-specific properties that set it apart from other liquids.
A water molecule is made up of two hydrogen (H) atoms and one oxygen (O) atom (O). Scientists use several methods to depict the formation of molecules. Oxygen molecule in water shown below was drawn using ball-and-stick model where each atom is represented by a small ball coated with electrons.
Hydrogen and oxygen combine to form H2O. This means that one molecule of H2O can create two new molecules of H2O when it reacts with another substance. For example, if you put alcohol (ethyl alcohol) in water, it will react with some of the water molecules to create more alcohol molecules and fewer water molecules.
You can think of water as a chemical bond inspector who visits every single molecule in your body and makes sure that they are behaving themselves. If any molecules are found doing something wrong, such as having an odd number of electrons or not being symmetrical, then the water molecule reformer comes along and changes them back into good molecules of H2O.
There are many other substances that can be found in water. Some of them are ammonia, carbon dioxide, methane, phosphorous, sulfur, iron, and calcium. The most common element by mass is hydrogen (74.9%). Other elements present in small amounts include oxygen (25.1%) and helium (0.8%).