Interfacial Tension: Adhesive and Cohesive Forces

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Questions and Answers

What is the condition for adhesive forces between two liquids to be more than cohesive forces?

The cohesive forces within each liquid are negligible

The liquids are partially miscible

The liquids are completely immiscible

The interfacial tension between them is zero (correct)

What happens when two liquids are completely miscible?

They form a distinct boundary

They are immiscible

There is no interfacial tension between them (correct)

They repel each other

What is the relationship between adhesive forces and cohesive forces when they are in equilibrium?

Adhesive forces do not depend on cohesive forces

Adhesive forces are more than cohesive forces

Adhesive forces are less than cohesive forces

Adhesive forces are equal to cohesive forces (correct)

Which of the following is a characteristic of two immiscible liquids?

They have high interfacial tension Signup and view all the answers

What happens when the adhesive forces between two liquids are less than the cohesive forces?

The liquids are immiscible Signup and view all the answers

What happens if a substance is too lipophilic?

It dissolves completely in the oil phase and little appears at the interface Signup and view all the answers

What is the relationship between a substance's lipophilicity and its adsorption?

High lipophilicity results in negative adsorption in the bulk Signup and view all the answers

What is negative adsorption related to?

Materials that are found in the bulk of liquid Signup and view all the answers

What happens if a substance has a balance of lipophilicity and hydrophilicity?

The information is not sufficient to determine what happens Signup and view all the answers

What is the opposite of negative adsorption?

Positive adsorption Signup and view all the answers

What happens when a liquid spreads over a surface?

It covers all or a part of the surface Signup and view all the answers

What is the extent of surface coverage when a liquid spreads?

It covers all or a part of the surface Signup and view all the answers

What is the primary outcome when a liquid spreads over a substrate?

The liquid covers all or a part of the surface Signup and view all the answers

What is a possible consequence of a liquid spreading over a surface?

The surface is partially or fully covered Signup and view all the answers

What can be said about the surface after a liquid spreads over it?

It becomes partially or fully covered Signup and view all the answers

Where does electric neutrality occur when the counterions in the tightly bound, solvated layer equal the positive charge on the solid surface?

Plane bb′ Signup and view all the answers

What is the condition for electric neutrality to occur at plane bb′?

The counterions equal the positive charge on the solid surface Signup and view all the answers

What happens when the counterions in the tightly bound, solvated layer do not equal the positive charge on the solid surface?

Electric neutrality does not occur at either plane Signup and view all the answers

What is the role of the tightly bound, solvated layer in achieving electric neutrality?

It neutralizes the positive charge on the solid surface Signup and view all the answers

What is the significance of plane cc′ in the context of electric neutrality?

It is where electric neutrality occurs when the counterions do not equal the positive charge Signup and view all the answers

Why is it necessary to overcome certain forces when resuspending and redispersing particles?

To break the adhesive and cohesive forces between particles Signup and view all the answers

What type of forces are responsible for holding particles together?

Adhesive and cohesive forces Signup and view all the answers

What is the result of not overcoming the forces holding particles together?

The particles will remain aggregated Signup and view all the answers

What is the purpose of overcoming the forces holding particles together?

To resuspend and redisperse the particles Signup and view all the answers

What is required to redisperse particles?

Overcoming the adhesive and cohesive forces Signup and view all the answers

What is the primary reason why water can wet the glass?

Cohesive forces between water molecules are weaker than adhesive forces between water and glass Signup and view all the answers

What is the shape of the surface of the capillary tube that allows water to rise?

Concave Signup and view all the answers

What is the primary direction of the force experienced by molecules at the surface of a liquid?

Inward, toward the bulk Signup and view all the answers

What is the result of adhesive forces being greater than cohesive forces between water molecules?

Water spreads over the surface Signup and view all the answers

What is the reason for the inward force experienced by molecules at the surface of a liquid?

The molecules at the surface are subject to cohesive forces from the bulk Signup and view all the answers

What is the relationship between adhesive forces and the shape of the capillary tube?

Adhesive forces increase with a concave surface Signup and view all the answers

What is the significance of the concave surface in the context of water rising in the capillary tube?

It increases the adhesive forces between water and glass Signup and view all the answers

What is the net result of the force experienced by molecules at the surface of a liquid?

A minimization of the surface area of the liquid Signup and view all the answers

What is the relationship between the force experienced by molecules at the surface of a liquid and the surface tension?

The force experienced by molecules at the surface is a result of the surface tension Signup and view all the answers

What is the significance of the force experienced by molecules at the surface of a liquid in interfacial phenomena?

It plays a crucial role in shaping the interface between two liquids or a liquid and a solid Signup and view all the answers

What is the primary reason for the formation of micelles in the bulk?

The concentration of surface active molecules exceeds the critical micelle concentration Signup and view all the answers

What happens to the surface of the water as more surface active agent is added?

The surface of the water becomes saturated with surface active molecules Signup and view all the answers

What is the state of the surface of the water when micelles start forming?

The surface is saturated with surface active molecules Signup and view all the answers

What is the consequence of adding more surface active agent to the water beyond the point of saturation?

Micelles start forming in the bulk Signup and view all the answers

What is the critical point at which micelles start forming in the bulk?

When the surface is saturated with surface active molecules Signup and view all the answers

What is the effect of a low concentration of surfactant on the activity of an anthelmintic drug?

It potentiates the activity of the drug. Signup and view all the answers

What is the significance of surfactants in the context of drug activity?

They can either enhance or inhibit the activity of anthelmintic drugs, depending on the concentration. Signup and view all the answers

What is the relationship between surfactant concentration and anthelmintic drug activity?

A low concentration of surfactant can potentiate the activity of anthelmintic drugs. Signup and view all the answers

What is the primary effect of a low concentration of surfactant on the activity of anthelmintic drugs?

It increases the potency of the drug. Signup and view all the answers

What is the implication of a low concentration of surfactant on the efficacy of anthelmintic treatment?

It increases the efficacy of the treatment. Signup and view all the answers

What is typically found in the region adjacent to the surface layer?

Tightly bound solvent molecules and negative ions Signup and view all the answers

What is the primary composition of the layer tightly bound to the surface?

Solvent molecules and negative ions Signup and view all the answers

What type of ions are typically found in the region adjacent to the surface layer?

Only negative ions Signup and view all the answers

What is the characteristic of the solvent molecules in the region adjacent to the surface layer?

They are tightly bound to the surface Signup and view all the answers

What is the relationship between the solvent molecules and ions in the region adjacent to the surface layer?

The solvent molecules attract the ions Signup and view all the answers

What happens if a molecule is too hydrophilic?

It remains within the body of the aqueous phase and exerts no effect at the interface Signup and view all the answers

What is the effect of a molecule's hydrophilicity on its behavior at the interface?

It decreases its adsorption Signup and view all the answers

What determines whether a molecule exerts an effect at the interface?

Its hydrophilicity Signup and view all the answers

What happens when a molecule is not adsorbed at the interface?

It remains within the body of the aqueous phase Signup and view all the answers

What is the result of a molecule being too hydrophilic?

It remains within the body of the aqueous phase Signup and view all the answers

What is the primary mode of death for cells exposed to cationic quaternary compounds?

Loss of essential materials Signup and view all the answers

What is the primary function of cationic quaternary compounds?

To disrupt cell membranes Signup and view all the answers

What is the likely outcome when a gram-positive organism is exposed to a cationic quaternary compound?

Cell membrane disruption Signup and view all the answers

What is the characteristic of the surface of a particle in relation to electric properties?

It has a positive charge Signup and view all the answers

What is the relationship between electric properties and interfacial phenomena?

They are directly related Signup and view all the answers

What happens to the surface of the substance when some of the cations are adsorbed onto it?

It becomes positively charged Signup and view all the answers

What is the result of the adsorption of cations onto the surface of the substance?

The surface becomes positively charged Signup and view all the answers

Why do some of the cations adsorb onto the surface of the substance?

To give the surface a positive charge Signup and view all the answers

What is the effect of the adsorption of cations on the surface properties of the substance?

It gives the surface a positive charge Signup and view all the answers

What is the consequence of the adsorption of cations onto the surface of the substance?

The surface becomes positively charged Signup and view all the answers

What is the potential at the solid surface due to the potential-determining ion defined as?

The difference in potential between the actual surface and the electroneutral region of the solution Signup and view all the answers

What is the significance of the electrothermodynamic potential?

It is the potential difference between the actual surface and the electroneutral region of the solution Signup and view all the answers

What is the role of the electroneutral region of the solution?

It is the region where the electroneutralization of the solid surface occurs Signup and view all the answers

What is the relationship between the electrothermodynamic potential and the solid surface?

The electrothermodynamic potential is dependent on the solid surface Signup and view all the answers

What is the condition for the electrothermodynamic potential to be significant?

When the electroneutral region of the solution is adjacent to the solid surface Signup and view all the answers

What is a characteristic of flocculated particles?

They settle rapidly Signup and view all the answers

What happens when flocculated particles settle?

They settle rapidly Signup and view all the answers

What is a characteristic of the bond between flocculated particles?

It is weak and flexible Signup and view all the answers

What can be done to flocculated particles once they have settled?

They can be resuspended Signup and view all the answers

What is NOT a characteristic of flocculated particles?

They form a hard cake Signup and view all the answers

Study Notes

Adhesive and Cohesive Forces

Adhesive forces between two liquids are greater than cohesive forces within the liquids
If two liquids are completely miscible, no interfacial tension exists between them

Interfacial Phenomena

When a liquid spreads over a surface, it covers all or part of the surface
Adhesive forces between a liquid and a surface can cause the liquid to rise in a capillary tube with a concave surface (e.g., water and glass)

Surfactants and Interfacial Tension

Surfactants can affect the activity of a drug, with a low concentration of surfactant potentiating the activity of an anthelmintic drug
As more surface-active agents are added to water, the surface of the water is covered by molecules of the surface-active agent, leading to micelle formation

Micelle Formation

Micelles are formed when surface-active agents are added to water, causing them to aggregate and form spherical structures
Micelle formation occurs when the surface of the water is saturated with surface-active molecules, and any increase in their concentration causes them to form micelles in the bulk

Electrical Properties of Interfaces

Electric properties of interfaces refer to the charge on the surface of a particle
The potential at the solid surface is defined as the electrothermodynamic (Nernst) potential, which is the difference in potential between the actual surface and the electroneutral region of the solution
Flocculated particles are weakly bonded, settle rapidly, do not form a cake, and are easily resuspended

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Description

This quiz covers the relationship between adhesive and cohesive forces in liquids, and how it affects interfacial tension. Learn about the conditions under which interfacial tension exists or disappears.