Questions and Answers
What is the main characteristic of lyophilic colloids?
Which of the following is an example of a lyophobic colloid?
What is the characteristic feature of gels?
What is the Tyndall effect?
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Which of the following is an example of an emulsion?
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What is the function of emulsifying agents or surfactants in emulsions?
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What is the main difference between lyophilic and lyophobic colloids?
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What is the characteristic of the scattered light in the Tyndall effect?
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Study Notes
Colloidal Solutions
Lyophilic Colloids
- Also known as hydrophilic colloids
- Particles or molecules are strongly solvated by the dispersion medium (usually water)
- Examples: starch, gelatin, and proteins
- Properties:
- Reversible sol-gel transition
- High viscosity
- High stability due to solvation
Lyophobic Colloids
- Also known as hydrophobic colloids
- Particles or molecules are not solvated by the dispersion medium
- Examples: metal sols, sulfur sols, and clay suspensions
- Properties:
- Irreversible sol-gel transition
- Low viscosity
- Low stability due to lack of solvation
- Can be stabilized by adding emulsifying agents or surfactants
Gels
- Colloidal system in which the disperse phase has formed a network of particles
- Properties:
- Non-flowing, semi-rigid structure
- High viscosity
- Reversible sol-gel transition
- Examples: agar agar, gelatin, and silica gel
Tyndall Effect
- Scattering of light by colloidal particles
- Observed when a beam of light passes through a colloidal solution
- Properties:
- Scattered light is blue or violet due to shorter wavelengths
- Can be used to distinguish between colloidal solutions and true solutions
- Named after John Tyndall, who discovered the phenomenon
Emulsions
- Colloidal system in which two or more liquids are mixed
- Properties:
- One liquid is dispersed in another in the form of droplets
- Droplets are stabilized by emulsifying agents or surfactants
- Examples: mayonnaise, milk, and cream
- Can be classified as:
- Oil-in-water (O/W) emulsions
- Water-in-oil (W/O) emulsions
Colloidal Solutions
Lyophilic Colloids
- Strongly solvated by dispersion medium (usually water)
- Examples: starch, gelatin, and proteins
- Reversible sol-gel transition
- High viscosity
- High stability due to solvation
Lyophobic Colloids
- Not solvated by dispersion medium
- Examples: metal sols, sulfur sols, and clay suspensions
- Irreversible sol-gel transition
- Low viscosity
- Low stability due to lack of solvation
- Can be stabilized by emulsifying agents or surfactants
Gels
- Disperse phase forms network of particles
- Non-flowing, semi-rigid structure
- High viscosity
- Reversible sol-gel transition
- Examples: agar agar, gelatin, and silica gel
Tyndall Effect
- Scattering of light by colloidal particles
- Observed when light passes through colloidal solution
- Scattered light is blue or violet due to shorter wavelengths
- Distinguishes colloidal solutions from true solutions
- Named after John Tyndall
Emulsions
- Two or more liquids mixed
- One liquid dispersed in another as droplets
- Droplets stabilized by emulsifying agents or surfactants
- Examples: mayonnaise, milk, and cream
- Classifications:
- Oil-in-water (O/W) emulsions
- Water-in-oil (W/O) emulsions
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Description
Learn about the differences between lyophilic and lyophobic colloids, including their properties and examples. Understand the solvation and stability of colloidal particles in dispersion mediums.
