Surface Tension

For complete spreading (wetting) of the liquid over the surface, S should have a value of _____ or greater.

0

What is the average alveoli diameter in an adult?

200µm

Wetting of a powder is difficult if the contact angle is greater than _____.

90°

What is Young's Equation?

A_SL= γ_SL (1+ cosϴ)

How can you lower γLV?

Add a surfactant to the water or use another liquid with a lower γLV¬ to initially wet the particles.

What are some natural surfactants in the GI tract?

Bile salts

Surface tension is a phenomenon in which the surface of a liquid, where the liquid is in contact with gas, acts like a thin ______ sheet.

Elastic

What protein-free synthetic lung surfactant is used to dramatically reduce mortality and morbidity in premature infants suffering from, or at risk of RDS due to surfactant deficiency?

Exosurf Neonatal

What is the Marangoni Effect?

Fluids will flow from areas of low surface tension to areas of high surface tension.

What are the units for surface tensions (γ)?

Force per unit length (dyne/cm or erg/cm2)

Using the Young's Equation, if ASL is _____ than γLV, then the liquid is more likely to spread upon or wet the surface.

Greater

When the contact angle = 0°, the surface is perfectly wetted, meaning that the liquid/solid adhesive forces are much ______ than the liquid intermolecular cohesive forces.

Greater

When the contact angle is > 90°, the surface is not easily wetted, meaning the liquid intermolecular cohesive forces are ______ than the liquid/solid adhesive forces.

Greater

The smaller the particle, the ______ they are to wet.

Harder

Why is γ important in dispersed systems?

Helps explain wetting of surfaces and particles

Polar liquids have _____ surface tension than less polar or nonpolar liquids.

Higher

The greater the cohesive forces, the ______ the surface tension.

Higher

What intermolecular forces are present in water?

Hydrogen bonds

As the alveoli expand during inhalation, the surface tension ______ to a maximum and then during exhalation, the alveoli more easily contract.

Increases

If the surface is between two liquid, it is called ______ tension.

Interfacial

Higher molecular weight (longer) alkanes have ______ γ than shorter alkanes.

Larger

Using the Young's Equation, if ASL is _____ than γlv, then the liquid is less likely to spread upon or wet the surface.

Less

When the contact angle is < 90° but > 0°, the surface can be wetted, meaning that the liquid intermolecular cohesive forces are _____ than liquid/solid adhesive forces.

Lesser

Materials will flow from ______ γ to ______ γ.

Low; high

The smaller the contact angle, the _____ the surface tension a liquid displays in contact with a solid surface.

Lower

How can we improve the wettability of a surface?

Lower the surface tension

What is one way to reduce the pressure inside the bubble?

Lower the surface tension

Out of solids, _____ have high surface tensions.

Metals

For values of S (spreading coefficient) that are ______, the liquid is less likely to exhibit complete spreading or wetting of the solid (powder) surface.

Negative

What is the Young-LaPlace Law?

P= (2 ∙γ)/r

_______ γ is key to forming emulsion and to wetting some surfaces.

Reducing

What is the Young's Equation to determine the spreading coefficient (S)?

S= γ_LV (cosϴ)

At a specific surface tension, it take more pressure to inflate a ____ bubble than a ____ one.

Small; large

At a given surface tension, the _____ the radius of the bubble, the greater the pressure inside the bubble.

Smaller

The _______ the contact angle, the more the solid surface is wetted.

Smaller

A _____ shape yields the smallest surface area for a given volume (minimal surface).

Sphere

A chemical concentration or temperature gradient can cause the _____ _____ gradient.

Surface tension

Intermolecular forces determine the magnitude of γ (_____ _____).

Surface tension

What is the reason why liquids take the shape of spheres (drops) in air or other immiscible liquids?

Surface tension

Without lung _____, small alveoli would collapse because you couldn't generate enough air pressure during inflation to inflate them.

Surfactant

What are some natural surfactants in the eye?

Tears and tear film (lipids, proteins, phospholipids)

How do bile salts act as surfactants in the GI tract?

They form micelles to help solubilize and absorb lipids

What intermolecular forces are in nonpolar liquids?

Van der Waals

What is the most common pharmaceutical solvent?

Water

Knowing the contact angle can tell you how easy the surface can be ______.

Wetted