Water is a very important and an essential solution in this world. Water covers 75% of the earth surface which is part of the sea, rivers, and lakes. If there is no water in this world, there will be no life. In addition, 2/3 of the human body is also a water. Besides being used as a source for drinking, washing and cooking, water is also needed as a crop irrigation, road cleaning, heating and even can be used as a source of hydroelectricity.
Elements of Water Supply
Chemically, water is composed of hydrogen and oxygen to form H2O. The bond formed is a very strong hydrogen bond because there is a joint use of atm between hydrogen and oxygen. Atoms of oxygen have higher electron affinity values than hydrogen atoms, and electrons in hydrogen and oxygen bonds tend to move or converge on oxygen because of the extremely high electronegativity of oxygen.
Further, the H-O-H structure in water provides an angle value of 104.5 ° which gives the structure shape like a “V” letter. This is because the electrons contained in the oxygen atom which is the electronegative and the two hydrogen atoms that are electropositive form a polar compound. So, water is a polar compound.
Polar compounds can connect very easily with other polar compounds. The other way applied when it mixed with non-polar compounds, such as oil and water that can not be mixed. Further, the resulting hydrogen bonds give their own uniqueness.
What is that? A hydrogen bond can provide a low density on ice rather than water in a liquid state. One water molecule can form 4 hydrogen bonds with its neighboring molecule. Then, when the ice begins to melt, many of the hydrogen bonds begin to decompose, so it can be said that water molecules in the liquid state have a higher density than in solid state.
Water also has a high boiling point for small molecules. The boiling point of water is at 100oC. To make the water boil, it takes enough energy to give vibration to the hydrogen bonds in the water. What distinguishes the boiling point between water and the compounds that form other hydrogen bonds such as H2S is the molar mass of the compound.
The higher the molar mass, the temperature required to boil water will be higher. It is also work for the melting point of the compound.
The Elements of Water Supply
| Compounds | Boiling Point (oC) | Melting Point (oC) |
| H2O | 100 | 0 |
| HF | 19,5 | -83,6 |
| NH3 | -33,34 | -77,73 |
| CH4 | -161,5 | -182 |
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In addition to these elements, there are several other elements that greatly form the characteristics of water such as:
- pH: parameters used to determine whether the water has acidic, neutral or alkaline characteristics
- Turbidity: Which is used to show TSS in water.
- Calcium and Magnesium: Is a parameter used to determine the level of water hardness.
- Total iron content: Fe contained in water. If it is too high, it can cause the water to turn yellow and smell bad.
- Ammonium ion: This concentration can make high NH3 levels and accelerate the corrosion of copper by forming a copper-ammonium salt compound, so it is not safe i because it can cause leaks in the pipes.
- BOD (Biochemical Oxygen Demand): Higher concentrations of BOD will make the water harmful because of the high oxygen required for organisms to damage certain organic material compounds.
Water Phase Diagram
Water has abnormal phase diagrams because of lower ice density rather than liquid density. Le Chatelier’s principle shows that the denser phases have an advantage because of the increased pressure to become water, the effect of increasing pressure on the lower ice phases causes the melting of ice to be a larger liquid phase than its density.
This is the nature of water anomalies that allow people to play ice skating on the ice. If the pressure of the ice skates is enough to melt the ice on the surface so that the water layer that occurs makes the shoe can slide easily even at -300 ° C.
The structure of the water itself is very important. The ice structure is very good to be studied to know the structure of water. The ice formed in equilibrium with water at 0 ° C and at 1 atm has an ice structure in general. There is an infinite order of oxygen atoms, each of which is surrounded by an O atom with a tetrahedral structure with a hydrogen bond.
Actually, there are still a lot of debates about the structure of the water. The structure is not random as it is in nature that consists of polar molecules and there are also a few non-polar molecules in the form of spheres. However, the structure contained in the water has a regularity due to the presence of hydrogen bonds. In the ice structure, the oxygen atom atom has a distance of 2.75A. Then, in a water model, it has several things between them, such as:
- Some interstitials contain water molecules that do not belong to the network but instead annoy them
- The network is a “patch” and does not extend over a long distance without breaking
- Short areas of the region are re-established
- Networks are somewhat evolved when compared to ice in general
Water Cycle
The water in the earth is always moving. Water moves from land or from sea to the atmosphere and forms clouds and then drops back to the so-called water cycle. Water, air, sun, gravity play an important role in providing the water cycle.
The heat from the sun causes the evaporation of water. Then because there is moisture pressure and temperature in the atmosphere then formed a cloud. Which is the water point. Then gravity keeps the water down back to the soil called rain.