Surface tension is caused by the inward attraction of molecules at a boundary.
Surface tension is the energy required to stretch a unit change of surface area - and the surface tension will form a drop of liquid to a sphere since the sphere offers the smallest area for a definite volume.
Surface tension can be defined as
σ = Fs / l (1)
σ = surface tension (N/m)
Fs = stretching force (N)
l = unit length (m)
Alternatively, surface tension is typically measured in dynes/cm, which is
- the force in dynes required to break a film of length 1 cm
or as surface energy J/m2 or alternatively ergs per square centimeter.
- 1 dynes/cm (dyn/cm) = 0.001 N/m = 0.0000685 lbf/ft = 0.571 10-5 lbf/in = 0.0022 poundal/ft = 0.00018 poundal/in = 1.0 mN/m = 0.001 J/m2 = 1.0 erg/cm2 = 0.00010197 kgf/m
Common Imperial units used are lb/ft and lb/in.
Surface Tension of Water
Surface tension of water at some temperatures:
- σ -
Surface Tension of some common Fluids
Surface tension of fluids at 25oC (77oF).
|Acetic acid, Ethanoic acid||0.027|
|Acetic anhydride, Acetyl acetat||0.032|
|Acetonitrile, Methyl cyanide||0.287|
|Benzonitrile, Phenyl cyanide||0.039|
|1-Butanol, Butyl alcohol||0.025|
|Clorobenzene, Phenyl chloride||0.033|
|1-Chlorohexane, Hexyl chloride||0.026|
|Diethyl ether, Ethyl ether||0.017|
|Diethyl sulfide, Ethyl sulfide||0.025|
|Ethanol, Ethyl Alcohol, Pure Alcohol, Grain Alcohol, Drinking Alcohol||0.022|
|Formixc acis, Methanoic acid||0.037|
|Heptanoic acid, Enanthic acid||0.028|
|1-Hexanol, Caproyl alcohol||0.026|
|Isobenzene, Phenyl iodide||0.039|
|Isobutyl acetat. 2-Methylpropyl acetat||0.023|
|Isopropanol, 2-propanol, Isopropyl Alcohol, Rubbing Alcohol, Sec-propyl Alcohol, s-Propanol||0.022|
|Methanol, Methyl alcohol||0.022|
|1-Propanol, Propyl alcohol||0.023|
|Water at 20oC||0.072|
|Water, soapy at 20oC||0.0250 - 0.0450|
|Water-d2, Heavy Water||0.071|
Surface Active Agents
Soaps, detergents or surfactants - also called surface-active agents - added to to water even in small substances decreases the surface tension of water to a considerable extent. Due to decreased surface tension water with soap can remove oil or grease where clean water can not.
The study of fluids - liquids and gases. Involving velocity, pressure, density and temperature as functions of space and time.
Chemical, physical and thermal properties of acetone, also called 2-propanone, dimethyl ketone and pyroacetic acid. Phase diagram included.
Chemical, physical and thermal properties of benzene, also called benzol. Phase diagram included.
Capillarity - or capillary action - is the ability of a narrow tube to draw a liquid upwards against the force of gravity.
Chemical, physical and thermal properties of ethylene, also called ethene, acetene and olefiant gas. Phase diagram included.
Surface tension of water in contact with air for temperatures ranging 0 to 100oC (32 to 212oF) - in imperial units (BG units) and SI units.
The Weber Number may be useful when analyzing fluid flows where there is an interface between two different fluids.