Podcast
Questions and Answers
What distinguishes interfacial tension from surface tension?
What distinguishes interfacial tension from surface tension?
- Interfacial tensions are typically greater than surface tensions due to the stronger cohesive forces between different phases.
- Interfacial tensions are generally lower than surface tensions because the adhesive forces between two liquid phases are greater than those between a liquid and a gas phase. (correct)
- Interfacial tensions exist only when two miscible liquids are in contact, while surface tensions occur in immiscible liquids.
- Interfacial tensions involve adhesive forces between a liquid and a gas phase, whereas surface tensions relate to interactions within a single liquid phase.
How does temperature affect surface tension, and what is the underlying reason for this effect?
How does temperature affect surface tension, and what is the underlying reason for this effect?
- Surface tension remains constant with temperature as the effects of kinetic energy and intermolecular forces balance each other out.
- Surface tension increases with temperature due to increased molecular kinetic energy and decreased cohesive forces.
- Surface tension decreases with temperature because the increased molecular motion overcomes the intermolecular forces, leading to reduced cohesion. (correct)
- Surface tension fluctuates randomly with temperature due to unpredictable changes in molecular arrangement.
How does the complete miscibility of two liquids influence interfacial tension, and why does this occur?
How does the complete miscibility of two liquids influence interfacial tension, and why does this occur?
- Complete miscibility has no effect on interfacial tension as the liquids mix uniformly.
- Complete miscibility increases interfacial tension due to enhanced adhesive forces between the liquids.
- Complete miscibility reduces interfacial tension because the stronger cohesive forces prevent an interface from forming.
- Complete miscibility results in zero interfacial tension because there is no distinct interface formed. (correct)
Under what conditions can the capillary rise method accurately measure liquid properties, and what limitations apply?
Under what conditions can the capillary rise method accurately measure liquid properties, and what limitations apply?
What does surface energy represent, and how is it related to surface tension?
What does surface energy represent, and how is it related to surface tension?
How does the force of gravity relate to the concepts of surface tension in the drop weight and drop count methods?
How does the force of gravity relate to the concepts of surface tension in the drop weight and drop count methods?
What implications does higher surface energy have for the interfacial contact between phases, and why?
What implications does higher surface energy have for the interfacial contact between phases, and why?
A researcher observes that the surface tension of a liquid decreases significantly with increasing temperature. Which phenomenon contributes to this observation?
A researcher observes that the surface tension of a liquid decreases significantly with increasing temperature. Which phenomenon contributes to this observation?
In capillary action, a liquid rises in a narrow tube due to surface tension. Which factor would cause a liquid with a given surface tension to rise higher in the tube?
In capillary action, a liquid rises in a narrow tube due to surface tension. Which factor would cause a liquid with a given surface tension to rise higher in the tube?
In a scenario where two immiscible liquids are mixed, what would indicate complete miscibility has been achieved regarding interfacial tension?
In a scenario where two immiscible liquids are mixed, what would indicate complete miscibility has been achieved regarding interfacial tension?
When measuring surface tension using the drop weight method, which alteration to the procedure would likely result in a more accurate determination of surface tension?
When measuring surface tension using the drop weight method, which alteration to the procedure would likely result in a more accurate determination of surface tension?
In the context of surface and interfacial tension, how would increasing the area of interfacial contact typically influence the system's energy state, and why?
In the context of surface and interfacial tension, how would increasing the area of interfacial contact typically influence the system's energy state, and why?
Consider a scenario where two liquids are placed in contact, and the adhesive forces between them are significantly weaker than their cohesive forces. How is this interaction expected to influence interfacial tension?
Consider a scenario where two liquids are placed in contact, and the adhesive forces between them are significantly weaker than their cohesive forces. How is this interaction expected to influence interfacial tension?
Which modification would enhance the precision of measurements obtained via the capillary rise method?
Which modification would enhance the precision of measurements obtained via the capillary rise method?
How would choosing a volatile liquid affect the surface tension measurement via the drop weight method?
How would choosing a volatile liquid affect the surface tension measurement via the drop weight method?
In the context of surface tension, what represents the most stable configuration for liquid droplets?
In the context of surface tension, what represents the most stable configuration for liquid droplets?
If two liquids mixed show a high value for interfacial tension, what can most likely be inferred?
If two liquids mixed show a high value for interfacial tension, what can most likely be inferred?
In what way does the density of a liquid play a critical role in surface tension measurement using capillary rise method?
In what way does the density of a liquid play a critical role in surface tension measurement using capillary rise method?
What precautions should be taken into consideration during the drop count method?
What precautions should be taken into consideration during the drop count method?
What does zero contact angle imply, and what can be inferred?
What does zero contact angle imply, and what can be inferred?
How can surface tension affect drug formulation?
How can surface tension affect drug formulation?
If an experimental setup increases surface tension, what changes can be expected from the equilibrium?
If an experimental setup increases surface tension, what changes can be expected from the equilibrium?
Which scenario best describes a condition of equilibrium associated with minimized surface energy?
Which scenario best describes a condition of equilibrium associated with minimized surface energy?
What is the link between lower energy states and surface tension?
What is the link between lower energy states and surface tension?
Increasing interfacial contact would reduce which measure related to surface interactions?
Increasing interfacial contact would reduce which measure related to surface interactions?
Flashcards
Interface
Interface
The boundary between 2 phases in contact with each other.
Surface
Surface
The boundary between 2 phases where one of them is a gas or vapor.
Adhesion Force
Adhesion Force
The attraction force between molecules of different phases.
Cohesion Force
Cohesion Force
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Surface Tension
Surface Tension
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Interfacial Tension
Interfacial Tension
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Interfacial vs. Surface Tension
Interfacial vs. Surface Tension
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Surface Energy
Surface Energy
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Capillary Rise Method
Capillary Rise Method
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Drop Weight Method
Drop Weight Method
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Drop Count Method
Drop Count Method
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Study Notes
Course Specifications
- This course is for the Pharm D Clinical and Pharm D programs.
- The course is a major or minor element of Pharmaceutics programs.
- The Department of Pharmaceutics offers the program.
- The Department of Pharmaceutics and Industrial Pharmacy offers the course.
- The academic year is 2020/2021, and the level is Level 1, Semester 2 (Spring).
- The course name is Physical Pharmacy, and the course code is PT 202.
- Total credit hours are 3 hrs, with 2 hrs for lecture and 1 hr for tutorial/practical.
Calendar 2019/2020
- Surface tension involves attraction forces, adhesive forces, and cohesive forces.
- Includes surface active agents, surfactant structures, and surfactant classifications.
- The HLB system should be understood.
- Critical micelle concentration (CMC) is studied, including micelle structures.
- Pharmaceutical uses for surface active agents are explained.
- Polymorphism definition, crystal structure, and exterior appearance are important.
- Study of pharmaceutical implications of polymorphism.
- Includes crystal solvates, crystal hydrates, and pseudopolymorphic solvates.
- Differences between crystal solvates and anhydrates are important.
- Solubility definitions: saturated, unsaturated (subsaturated), and supersaturated solutions.
- Qualitative, quantitative, percentage, molarity, normality, and molality solubility expressions.
- Types of solutions must be understood.
- Factors impacting solid and gas solubility in liquids are studied.
- Henry's and Raoult's Laws are studied.
- Liquids in liquids and ideal vs non-ideal solutions are considered.
- Diffusion is defined.
- Fick's first and second laws of diffusion is significant.
- Absorption from biological membranes is studied.
Calendar 2019/2020 (cont.)
- Colligative properties of solutions are important.
- Includes explanations and applications of colligative properties.
- Study of buffer solutions and buffer action.
- Understanding how weak acid/base mixtures behave is significant.
- Henderson-Hasselbalch equation for acidic and basic buffers are important.
- Buffer capacity and pH factor of buffer solutions should be understood.
- Includes biological, pharmaceutical, and buffered isotonic solutions.
- Adsorption, sorption, and desorption are defined.
- Study of types of adsorption and affecting factors.
- Understanding adsorption isotherms is important.
- Pharmaceutical applications of adsorption are studied.
- Understand rheology, tensile strength, and shear stress.
- Includes Newtonian and non-Newtonian flow and viscosity definitions.
- Study of pharmaceutical applications of rheology.
- Partition coefficient defined and factors are recognized.
Student Assessment
- Assessment uses written finals and quizzes to assess knowledge.
- Oral exams evaluates student understanding and ability to communicate.
- Practical exams test skills in compounding and dispensing dosage forms.
- Practical lesson evaluations measure effective participation.
Assessment Schedule
- 1st Quiz is scheduled for week 1.
- 2nd Quiz is scheduled for week 2.
- Practical Examination will be held on week 3.
- Week 4 is allocated for the Final Written Examination.
- Oral exams are scheduled for week 5.
- Quizzes contributes to 15 marks.
- Oral contributions contributes to 10 marks.
- Practical work will contribute 25 marks.
- The final term examination contributes to 50 marks.
- The total assessment marks amounts to 100.
Surface and Interfacial Tension
- Interface is the boundary between 2 phases in contact, like liquid-liquid or solid-liquid.
- Surface exists as the boundary between 2 phases if one of them is a gas or vapor.
- No interface exists between two gases since they mix.
- Adhesion force is the attraction between molecules of different phases.
- Cohesion force is the attraction between molecules of the same phase.
- Cohesion maintains phase separation, while adhesion promotes phase affinity.
- Stronger adhesion forces lead to miscibility.
- Molecules at a surface lack proper attraction force and causes contraction, resulting in surface tension.
Surface Tension
- Surface tension is the force per unit length on a liquid surface opposing expansion and measured in dyne/cm.
- It is the force/unit length needed to balance the inward pull of molecules at the interface.
Interfacial Tension
- Exists at the interface between two immiscible liquids.
- Interfacial tension's unit is dyne/cm.
Surface and Interfacial Tension Comparison
- Interfacial tensions are less than surface tensions given stronger adhesive forces between liquid phases.
- No interfacial tension exists if liquids are completely miscible.
- Greater surface tension means greater intermolecular attraction.
- Surface tension is inversely proportional to temperature causing reduced cohesive force.
Surface Energy
- Potential energy of a molecule on the surface is higher than those of the liquid.
- Surface energy equals work needed to create a unit, and is known as surface free energy.
- Surface energy is equivalent to surface tension.
Surface Tension and Surface Energy Relationship
- The greater the interfacial contact area, the greater the free energy.
- At equilibrium, surface free energy must be minimal.
- Liquid droplets form spherical shapes to reduce surface area.
Measurement of Surface and Interfacial Tension
- The capillary rise method is ideal for measuring surface tension.
- It measures the liquid's rise in a capillary tube.
- Equilibrium exists between surface tension's upward force and liquid weight's downward force.
- With the drop weight and drop count method, liquid is slowly allowed to drop making measurement possible.
Capillary Rise Method Equation
- γ = (1/2) * r * h * ρ * g: γrepresents the surface tension, r is the radius of the capillary.
- h refers to the height of the liquid in the capillary tube, ρ refers to the density of the liquid and g refers to the gravity constant.
Other Measurements
- Drop weight uses a stalagmometer with two marks.
- Liquid is drawn between marks to measure drop number and weight to determine surface tension.
- Drop count involves filling the stalagmometer between two points and counting to apply the equation.
- The process can then can find relative surface tension of a liquid.
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