Our Lady of Fatima University
College of Pharmacy
Physical Pharmacy
INTERFACIAL PHENOMENA AND SURFACE TENSION
1. What is surface tension and interfacial phenomena? Explain the principle behind surface tension and
interfacial phenomena.
Surface tension - The energy necessary to raise the surface area of a liquid attributable to intermolecular forces
is referred to as surface tension. As these intermolecular forces differ based on the composition of the liquid for
example water vs. gasoline or the solutes in the liquid, each solution has a different surface tension. The
principle underlying surface tension is centered on the molecular theory of matter. Cohesive forces amongst
liquid molecules, as per this notion, are responsible for the observation of surface tension. It is because the
molecules deep within the liquid are tugged uniformly in all directions by the other molecules causing the
molecules on the surface get pulled inward.
Interfacial phenomena - Interfacial phenomena happen when two distinct phases, such as a solid and a liquid,
or even a liquid and a gas, come together. Physical and chemical alterations at these interactions may result to
significant innovation. The underlying principle of interfacial phenomena is that if two liquids are entirely miscible,
there is no interfacial tension connecting them. Also, greater surface tension implies a stronger intermolecular
force of attraction, hence a gain in hydrogen bonds or molecular weight generates an increase in surface
tension.
2. Explain the factors which affect surface tension?
Intermolecular forces - It influences surface tension in such a way that the greater the intermolecular forces,
the greater the surface tension.
Temperature - Because cohesive forces reduce with increased molecule thermal activity, it influences surface
tension in such a way that surface tension falls as temperature rises. The adhesion effect of liquid molecules at
the interaction allows the surrounding environment to have an impact.
3. Give and describe the instruments used in measuring surface tension and interfacial phenomena.
Volumetric tensiometers - Used to measure head and pressure, tensiometer is made out of a fine-grained
porous ceramic cup linked to a water-filled sealed pipe. The water pressure at the top of the sealed tube is
measured by a pressure gage linked to the sealed tube.
Du Nouy - This instrument makes use of the interaction of a platinum ring with the liquid's surface. By shifting
the stage where the liquid container is situated, the ring is submerged below the interface. Following immersion,
the stage is progressively lowered, and the ring pushes up the liquid's meniscus. This meniscus eventually
breaks away from the ring. Before the ripping event, the volume of the meniscus reaches its greatest value and
begins to decline.
Wilhelmy plate - It is commonly used to quantify surface or interfacial tension at air-liquid or liquid-liquid
interfaces. This method involves measuring the force F acting on a partly immersed plate in liquid.
Pendant drop - It is a drop hanging from a needle in a bulk liquid or gaseous phase. The form of the drop is
determined by the connection between surface tension or interfacial tension and gravity. The surface tension or
interfacial tension of a pendant drop is estimated using drop shape analysis from the shadow picture of a
pendant drop in the pendant drop technique.
Bubble pressure - This approach suggests that a gas bubble is inflated in a fluid by supplying gas at a
regulated pressure. When the radius of the bubble matches the radius of the capillary, the pressure is at its
maximum. Extending the bubble further reduces the pressure and causes the bubble to separate.
College of Pharmacy
Physical Pharmacy
INTERFACIAL PHENOMENA AND SURFACE TENSION
1. What is surface tension and interfacial phenomena? Explain the principle behind surface tension and
interfacial phenomena.
Surface tension - The energy necessary to raise the surface area of a liquid attributable to intermolecular forces
is referred to as surface tension. As these intermolecular forces differ based on the composition of the liquid for
example water vs. gasoline or the solutes in the liquid, each solution has a different surface tension. The
principle underlying surface tension is centered on the molecular theory of matter. Cohesive forces amongst
liquid molecules, as per this notion, are responsible for the observation of surface tension. It is because the
molecules deep within the liquid are tugged uniformly in all directions by the other molecules causing the
molecules on the surface get pulled inward.
Interfacial phenomena - Interfacial phenomena happen when two distinct phases, such as a solid and a liquid,
or even a liquid and a gas, come together. Physical and chemical alterations at these interactions may result to
significant innovation. The underlying principle of interfacial phenomena is that if two liquids are entirely miscible,
there is no interfacial tension connecting them. Also, greater surface tension implies a stronger intermolecular
force of attraction, hence a gain in hydrogen bonds or molecular weight generates an increase in surface
tension.
2. Explain the factors which affect surface tension?
Intermolecular forces - It influences surface tension in such a way that the greater the intermolecular forces,
the greater the surface tension.
Temperature - Because cohesive forces reduce with increased molecule thermal activity, it influences surface
tension in such a way that surface tension falls as temperature rises. The adhesion effect of liquid molecules at
the interaction allows the surrounding environment to have an impact.
3. Give and describe the instruments used in measuring surface tension and interfacial phenomena.
Volumetric tensiometers - Used to measure head and pressure, tensiometer is made out of a fine-grained
porous ceramic cup linked to a water-filled sealed pipe. The water pressure at the top of the sealed tube is
measured by a pressure gage linked to the sealed tube.
Du Nouy - This instrument makes use of the interaction of a platinum ring with the liquid's surface. By shifting
the stage where the liquid container is situated, the ring is submerged below the interface. Following immersion,
the stage is progressively lowered, and the ring pushes up the liquid's meniscus. This meniscus eventually
breaks away from the ring. Before the ripping event, the volume of the meniscus reaches its greatest value and
begins to decline.
Wilhelmy plate - It is commonly used to quantify surface or interfacial tension at air-liquid or liquid-liquid
interfaces. This method involves measuring the force F acting on a partly immersed plate in liquid.
Pendant drop - It is a drop hanging from a needle in a bulk liquid or gaseous phase. The form of the drop is
determined by the connection between surface tension or interfacial tension and gravity. The surface tension or
interfacial tension of a pendant drop is estimated using drop shape analysis from the shadow picture of a
pendant drop in the pendant drop technique.
Bubble pressure - This approach suggests that a gas bubble is inflated in a fluid by supplying gas at a
regulated pressure. When the radius of the bubble matches the radius of the capillary, the pressure is at its
maximum. Extending the bubble further reduces the pressure and causes the bubble to separate.
