Factors that affect the surface tension of water is:
a) Temperature; at high temperature decreases the surface tension of water.
b) organic material and dissolved salts. The increase in salinity cause an increase in surface tension.
Figure 15. Insects that can survive on the surface of the water due to surface tension
Paremeter degree of acidity (pH of water)
Water never are in a state of absolutely pure. Materials / elements contained in the water generally comes from the land, air and water bodies metabolism. Elements / materials can be categorized into three groups, namely: (1) gas, (2) inorganic elements, and (3) organic. The third distribution group elements / chemicals mentioned above, largely determines the chemical properties of water. Elements / chemicals contained in existing water-soluble and insoluble there.
In general, inorganic elements is a chemical element that can be dissolved, except elemental sulfur (S) .Therefore because it is in the water, the elements are classified on the element of “macro and micro”. The degree of acidity is often known as the pH (negative puissance de H) is the logarithm of the concentration of ions H (hydrogen) are separated in a liquid. Acidic hydrogen ions. The existence of hydrogen ions describe the pH value (acidity) at a certain temperature or can be written by the equation pH = – log [H +].
Therefore, pure water has a pH value of 7. The higher the concentration of H + ions, then the lower OH- ions, so that the pH reached a value of <7 (acid waters). Conversely, if the OH- ion concentration higher than the concentration of H + ions, the alkaline nature of these waters because it has a pH value> 7. The hydrogen ion is an element that is very influential on other chemical factors, such as alkalinity, hardness and acidity of the water.
There are two ways of expressing (formulate) of H ions in water are:
a) Represents the number of molecules of hydrogen ions per liter of water.
b) the pH of the water which was formulated as follows:
c) pH = – log (H +)
H ion concentration or pH of the water is one of the chemical factors that greatly affect the lives of organisms that live in an aquatic environment. From both these expressions indicate the pH of the water can be measured and the pH value ranging between 0-14. At certain pH can describe the state of the water is acidic or alkaline.