Podcast
Questions and Answers
What is the term for the boundary that separates two different phases of matter?
What is the term for the boundary that separates two different phases of matter?
- Phase line
- Interface (correct)
- Boundary layer
- Surface area
Why do polar liquids typically have higher surface tensions than non-polar liquids?
Why do polar liquids typically have higher surface tensions than non-polar liquids?
- They have less viscosity
- They exhibit stronger hydrogen bonds (correct)
- They have higher molecular weight
- They contain fewer molecules
What is the equation relating work done to increase surface energy?
What is the equation relating work done to increase surface energy?
- $dW = eta . dT$
- $dW = au . dA$
- $dW = au . dS$ (correct)
- $dW = ho . dS$
What happens during the creation of new surfaces?
What happens during the creation of new surfaces?
In the MKSA system, how is surface tension ($ au$) expressed?
In the MKSA system, how is surface tension ($ au$) expressed?
What is the primary factor that causes variations in surface tension among different liquids?
What is the primary factor that causes variations in surface tension among different liquids?
If the energy of adhesion is greater than the energy of cohesion, what can be concluded about the wetting of the liquid?
If the energy of adhesion is greater than the energy of cohesion, what can be concluded about the wetting of the liquid?
Which equation correctly defines the spreading coefficient (S)?
Which equation correctly defines the spreading coefficient (S)?
What does it indicate if the spreading coefficient (S) is less than zero?
What does it indicate if the spreading coefficient (S) is less than zero?
What term is used to describe the attraction between molecules of the same substance?
What term is used to describe the attraction between molecules of the same substance?
In the equation $W_a = \sigma_L (1 + cos \theta)$, what does $\theta$ represent?
In the equation $W_a = \sigma_L (1 + cos \theta)$, what does $\theta$ represent?
What is the unit of work of cohesion ($W_c$) expressed in the context given?
What is the unit of work of cohesion ($W_c$) expressed in the context given?
Which of the following describes a condition of good wetting?
Which of the following describes a condition of good wetting?
What effect does a higher surface tension have on a liquid in a tube according to Jurin's Law?
What effect does a higher surface tension have on a liquid in a tube according to Jurin's Law?
In the context of alveoli, what occurs when smaller alveoli collapse into larger ones?
In the context of alveoli, what occurs when smaller alveoli collapse into larger ones?
What happens to the height of the liquid in a non-wettable tube?
What happens to the height of the liquid in a non-wettable tube?
Which statement correctly describes the nature of emulsions?
Which statement correctly describes the nature of emulsions?
How does the radius of the tube influence the height of the liquid according to Jurin's Law?
How does the radius of the tube influence the height of the liquid according to Jurin's Law?
What is the primary role of surfactants in emulsions?
What is the primary role of surfactants in emulsions?
What results when the angle θ is greater than π/2 in terms of the liquid's behavior in a tube?
What results when the angle θ is greater than π/2 in terms of the liquid's behavior in a tube?
What must occur to effectively create a foam?
What must occur to effectively create a foam?
What is the shape of the surface tension for a soap bubble?
What is the shape of the surface tension for a soap bubble?
How does increasing liquid density (ρ) affect the height (h) in a capillary tube?
How does increasing liquid density (ρ) affect the height (h) in a capillary tube?
Flashcards
Interface
Interface
The boundary between two different phases of matter, like solid-liquid, liquid-gas, or solid-gas.
Surface Tension
Surface Tension
The energy required to create a new surface. It's a measure of the force acting per unit length on the surface of a liquid.
Surface Energy
Surface Energy
The inherent energy associated with a surface. It increases when a new surface is created.
Surface Tension Units
Surface Tension Units
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Water's High Surface Tension
Water's High Surface Tension
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Cohesion
Cohesion
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Adhesion
Adhesion
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Cohesion Work (WC)
Cohesion Work (WC)
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Adhesion Work (Wa)
Adhesion Work (Wa)
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Spreading Coefficient (S)
Spreading Coefficient (S)
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Condition for Wetting
Condition for Wetting
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Contact Angle (ϴ)
Contact Angle (ϴ)
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Overpressure inside a droplet
Overpressure inside a droplet
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Laplace Pressure
Laplace Pressure
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Surface Tension (σ)
Surface Tension (σ)
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Capillary Rise (h)
Capillary Rise (h)
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Perfect Wetting
Perfect Wetting
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Non-Wetting
Non-Wetting
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Surface Tension Driven Collapse of Smaller Alveoli
Surface Tension Driven Collapse of Smaller Alveoli
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Emulsion
Emulsion
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Foam
Foam
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Study Notes
Chapter 01: Surface Phenomena
- Surface phenomena play a significant role in biological systems, acting as sites of intense molecular activity.
- Cellular surfaces are crucial for metabolic processes.
- Creation of new surfaces consumes energy.
- An interface is the boundary where two different phases of matter meet (e.g., solid-liquid, liquid-gas, solid-gas).
Surface Tension
- Surface tension (σ) is the energy required to increase the surface area of a liquid.
- Units for surface tension:
- MKSA system: J/m²
- CGSA system: erg/cm²
- 1 dyne = 10⁻⁵ N
- 1 erg = 10⁻⁷ J
- Bringing a molecule from the bulk to the surface requires work, increasing surface energy.
- Work (dW) = σ * dS (where dS is change in surface area)
Intermolecular Forces and Surface Tension
- Water has a high surface tension due to strong hydrogen bonding.
- Polar liquids have higher surface tensions than nonpolar liquids because of stronger intermolecular forces.
- Surface tension varies considerably between liquids based on intermolecular attractions.
Adhesion and Cohesion
- Adhesion: The attraction between molecules of different substances.
- Cohesion: The attraction between molecules of the same substance.
- These forces impact wetting characteristics.
Wetting
- Wetting describes how a liquid interacts with a surface.
- Contact angle (θ): The angle formed by the liquid-air interface and the solid-liquid interface.
- θ < 90°: Good wetting
- θ > 90°: Poor wetting
- θ = 180°: Non-wetting
- θ = 0°: Complete wetting
Spreading Coefficient (S)
- The spreading coefficient determines if a liquid spreads on a surface.
- S = Wa - Wc (where Wa is the adhesion work and Wc is the cohesion work)
- S > 0: Good wetting (liquid spreads)
- S < 0: Poor wetting (liquid doesn't spread)
Overpressure in Droplets and Bubbles
- Overpressure (ΔP) exists inside liquid droplets and bubbles, related to surface tension and radius.
- Spherical surface: ΔP = 2σ/R
- Cylindrical surface: ΔP = σ/R
- Soap bubble: ΔP = 4σ/r
- ΔP accounts for differences in pressure between the interior and exterior of a surface.
- Jurin's Law describes how liquid height in a capillary tube is related to surface tension and radius. Higher surface tension and smaller radius leads to higher liquid column in the tube.
Surfactants
- Surfactants reduce surface tension at the surface of alveoli in the lungs.
- Alveoli are better able to resist collapse with sufficient surfactant levels.
Foams & Emulsions
- Foams: Dispersions of gas in liquid, created by vigorous agitation.
- Emulsions: Dispersions of one liquid in another immiscible liquid. Surfactants stabilize emulsions by reducing interfacial tension and creating protective layers.
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