How do daily compounds such as table salt ($\ce{NaCl}$) and sugar ($\ce{C6H12O6}$) affect adhesion or surface tension of water? Considering their polarity, I guess they both increase it.
$\begingroup$
$\endgroup$
2
-
2$\begingroup$ Related: chemistry.stackexchange.com/questions/49570/… $\endgroup$– Ivan NeretinFeb 10, 2017 at 17:31
-
$\begingroup$ Salt and sugar are not surfactants but they are solutes when dissolved in water. $\endgroup$– MaxWFeb 10, 2017 at 22:24
Add a comment
|
1 Answer
$\begingroup$
$\endgroup$
The surface tension of water is increased by the dissolution of either glucose ($\ce{C6H12O6}$) or $\ce{NaCl}$. The following are excerpts from this table:
Solution$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ $ Temp ($\mathrm{^oC}$)$\ \ \ \ \ \ \ \ \ \ \ $ Surface Tension (mN/m)
Water$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ $25$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ $ 71.97
Water$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ $0$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ $ 75.46
6M aqueous $\ce{NaCl}$$\ \ \ \ \ \ \ \ $ 20$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ $ 82.55
Sucrose (55%) + water$\ \ $20$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ $ 76.45
(Water is included at two temperatures in order to bracket the temperature of the mixtures.)
According to this Wikipedia article:
Surfactants are compounds that lower the surface tension (or interfacial tension) between two liquids or between a liquid and a solid. Surfactants may [emphasis mine] act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants.
The article further states that "surfactant" is a concatenation of the term "surface acting agent". Furthermore, according to the Encylopaedia Britannica :
Surfactant, also called surface-active agent, substance such as a detergent that, when added to a liquid, reduces its surface tension, thereby increasing its spreading and wetting properties.
So, by these definitions and the data above, the compounds in question do not qualify as surfactants as they raise the surface tension of water. Additionally, as they have no amphiphillic (having both hydrophilic and lipophilic properties) nature, they would not be considered surfactants in the common context of chemistry jargon.