Water, washing and detergents

Detergents can also be very effective in helping grease and fats to be made soluble in water. An example of a soap is sodium stearate. It has a COO Na+ water-soluble end on a long carbon chain which is grease-soluble. Soaps can have a formula something like  

Similarly, an example of a detergent is CH3(CH2)2oC6H5S03 Na+ here the S03 Na+ group is the water-soluble group. Notice that sodium ions are present. This also aids solubility as most sodium salts are water-soluble (see also Section 4.11). 

Detergents also have the ability to lower the surface tension of water and wet surfaces of materials to make them accessible to water and washing. Water behaves as though it has a thin skin over its surface that has to be broken to get below its surface (flies and beetles use this when they walk over the surface of water). The action of soaps and detergents breaks down this surface layer. A mixture of water plus soap or a detergent can wash a material more effectively than water alone. 

We have mainly concentrated upon liquid water but the solid forms - ice, snow and hail - along with water vapour are also important items and worthy of further study. First we will briefly look at water vapour. 

There is water vapour in the air, as can be seen on a cold day when it condenses out of the air of a room onto the window panes of a house (unless they are double or triple glazed), or are even seen as we breathe out. Water vapour comes from any process of burning a hydrocarbon in oxygen, and that includes us as we burn up glucose in our bodies to produce energy plus the waste gases of C02 and H20. Our metabolic processes also produce water and water vapour, which we exhale in our breath. Plants do a similar thing. Cars, when they burn petrol, and power stations as they burn oil, gas or coal all produce water vapour. 

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