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Jihong Han's lectures > Surface and interfacial phenomena > Flashcards

Surface and interfacial phenomena Flashcards

1
Q

What do surfaces and interfaces affect?

A
  • It affects the dissolution of drugs (i,e total surface area and wetting and spreading)
  • It affects the absorption of many drugs (i.e dissolution and property biomembrane)
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2
Q

What is interface?

A

It is the boundary between two phases e.g oil and water

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3
Q

What is meant by a surface?

A

when one of the phases is gas/vapour eg surface of a cup of water. A surface is a special type of interface

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4
Q

The downward force is the origin of surface tension. TRUE OR FALSE/

A

TRUE

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5
Q

What is surface tension?

A

It is a horizontal force acting along the surface

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6
Q

After work is done to a system, the energy level of the system is lower. TRUE OR FALSE?

A

FALSE

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7
Q

When is a system more stable?

A

When its energy level is lower

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8
Q

Work can be converted into energy and vice versa. TRUE OR FALSE?

A

TRUE

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9
Q

Surface tension can be expressed as force per unit length of film. TRUE OR FALSE?

A

TRUE

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10
Q

Surface tension can be expressed as surface energy per unit area of film. TRUE OR FALSE?

A

TRUE

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11
Q

What is the equation for surface energy?

A

Surface tension * surface area

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12
Q

What is the equation for force?

A

Surface tension * Length

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13
Q

The larger the surface area, the higher the surface energy. TRUE OR FALSE?

A

TRUE

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14
Q

The higher the surface tension, the lower the surface energy. TRUE OR FALSE?

A

FALSE

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15
Q

What is the equation for surface tension?

A

ST = energy/Unit area

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16
Q

Surface tension is the free energy per unit area of the surface. TRUE OR FALSE?

A

TRUE

17
Q

Do solids have surface tension/interfecial tensions? Give example

A

YES e.g solid/air, solid/liquid

18
Q

The pressure inside a bubble is higher than atmospheric pressure outside. TRUE OR FALSE?

A

TRUE

19
Q

What is work adhesion?

A

Is the work required to separate the two phases at their interface

20
Q

What is work of cohesion?

A

Is work required to produce two new surfaces between the like molecules

21
Q

The larger the work of adhesion the stronger the attraction between the unlike surfaces. TRUE OR FALSE?

A

TRUE

22
Q

The larger the work of cohesion, the weaker the attraction between the like molecules. TRUE OR FALSE?

A

FALSE

23
Q

Work of adhesion is an indication of the attractive strength between unlike surfaces. TRUE OR FALSE?

A

TRUE

24
Q

Work of cohesion is an indication of the attractive strength between like surfaces. TRUE OR FALSE?

A

TRUE

25
Q

When does spreading occur?

A

It occurs if Spreading coefficient is greater than equals to 0 or when work of adhesion is greater than equal to work of cohesion.

26
Q

what is spreading coefficient calculated from?

A

Work of adhesion and cohesion

27
Q

With small contact angle, liquid/solid will spread. TRUE OR FALSE?

A

TRUE

28
Q

Contact angle is not affected by pressure. TRUE OR FALSE?

A

FALSE

29
Q

What are amphiphiles?

A

Both lipophilic and hydrophobic

30
Q

What are micelles?

A

Micelles are lipid molecules that arrange themselves in a spherical form in aqueous solutions. The formation of a micelle is a response to the amphipathic nature of fatty acids, meaning that they contain both hydrophilic regions (polar head groups) as well as hydrophobic regions (the long hydrophobic chain).

31
Q

What are the factors that affect adsorption?

A
  • Concentration of solute
  • Temperature - increased temp will increase adsorption
  • Surface area / increase in porosity will increases surface area
  • pH depending on species whether ionised or unionised

Jihong Han's lectures (11 decks)

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