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To convert a measurement from Newtons per meter to dynes per centimeter, you use the conversion factor that 1 N/m is equal to 1000 dyne/cm.
Example:
The surface tension of water is about 0.072 N/m. Convert this to dyne/cm.
0.072 N/m × 1000 (dyne/cm)/(N/m) = 72 dyne/cm
Answer: The surface tension of water is approximately 72 dyne/cm.
Surface tension is the tendency of liquid surfaces to shrink into the minimum surface area possible. It is a physical property that makes the surface layer of a liquid behave like a thin, stretched elastic sheet. This phenomenon is caused by cohesion—the attraction between similar molecules. Within the bulk of the liquid, each molecule is pulled equally in every direction by neighboring molecules, resulting in a net force of zero. At the surface, however, the molecules are pulled inwards by the molecules below them but have no corresponding upward pull from above. This creates an inward force at the surface that causes the molecules to pack together more tightly, minimizing their exposed surface area.
Surface tension is responsible for many familiar phenomena. It's what allows small insects, like water striders, to walk on the surface of a pond. It's what pulls water droplets into a nearly perfect spherical shape, as a sphere has the smallest surface area for a given volume. It's also what causes the capillary action that allows water to be drawn up into the narrow tubes of a plant's stem. The concept is crucial in chemistry, biology, and material science, influencing everything from the way detergents work to the design of inkjet printers and medical devices. The SI unit for surface tension is Newtons per meter (N/m), which can also be expressed as energy per unit area (Joules per square meter).
γ = F / L.ΔP = 2γ / r, where 'r' is the radius. For a bubble (which has two surfaces), it is ΔP = 4γ / r.h = (2γcosθ) / (ρgr), where 'γ' is the surface tension, 'θ' is the contact angle, 'ρ' is the liquid density, 'g' is the gravity, and 'r' is the tube radius.Soap and detergents are surfactants. Their molecules have a water-loving (hydrophilic) head and a water-fearing (hydrophobic) tail. They arrange themselves at the surface with their tails sticking out, which disrupts the strong cohesive hydrogen bonds between the water molecules. This weakens the inward pull and lowers the surface tension, allowing the water to spread out and wet surfaces more effectively.
Surface tension always tries to pull a liquid into the shape with the smallest possible surface area for a given volume. The geometric shape that satisfies this condition is a sphere. This is why raindrops, dewdrops, and soap bubbles are all spherical.
Insects like water striders can stand on water because their weight is distributed over their feet in a way that the force they exert on the surface is less than the force of the water's surface tension. The surface acts like a trampoline, bending under their weight but not breaking.
For most liquids, surface tension decreases as temperature increases. The increased thermal energy causes the molecules to move more vigorously, which weakens the cohesive forces between them, thereby reducing the tension at the surface.
Capillary action is the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity. It occurs because of the interplay between a liquid's surface tension (cohesion) and the adhesive forces between the liquid and the walls of the tube. This is how water is drawn up into a paper towel or into the roots of a plant.