What Is Water Equilibrium?

Water equilibrium can be defined as two completely different concepts. The first type has to do with water ions. When water is in its purest form, it contains an equal number of positive, negative, and neutral ions. The water must be perfectly pure for this to be observed because any additives will disturb and change the nature of the ions. The second kind of water equilibrium involves a small scale example of the water cycle. Those observing water turning to vapor and condensation inside a container should notice that the water level basically remains constant.

To obtain water that contains ionic equilibrium, science students must distill it using very clean instruments. These instruments should typically be heat sterilized in an oven so that they don’t have to be immersed in water or rubbed dry with a cloth. The water used to test water equilibrium should be previously distilled. Distilling already distilled water should yield the purest form of water possible. Students may use a solar still for this experiment, or they may use a distillation unit with tubes and a collection chamber. Either way, the still must also be carefully cleaned before use.

After the water has been distilled twice, it should be poured into a sterilized container. Students can use an anemometer or wires from a simple electrical circuit to see if the distillation helped achieve water equilibrium. If the water contains a balanced number of ions, it should conduct electricity fairly easily. An anemometer should record at least 0.5 volt of electricity passing through the water. The science students may also connect two wires to the clips on a light bulb holder and slip the other end of each wire into the water. If the water is balanced, it will complete the circuit and the light bulb will light.

When foreign objects — like silt, chemicals or other fluids — are introduced into water, they disrupt the ionic equilibrium. The highly distilled water described above contains an equal number of H₃O+, OH-, and H₂O neutral ions. Normally, the introduction of foreign objects will increase the number of neutral ions by causing some of the positive and negative ions to combine.

The second type of water equilibrium usually mimics the water cycle. In nature, the sun evaporates water from lakes, rivers, and the ocean to create vapor in the air. When the air becomes heavy with condensation, it falls back to the earth as rain. This same concept can be observed inside a covered jar filled about one-quarter full of water. If the jar is warmed, the water in the bottom of the jar will evaporate and travel to the top. Once there, it will cool into condensation. As the condensation builds, it will fall back into the bottom of the jar. Water equilibrium occurs under these circumstances because, no matter how much water appears to be in the jar, it is always the same amount.