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Questions and Answers
What is the property of hydrophilic sol colloids under changing conditions?
What is the process of converting a sol to a gel by cooling?
What is the state of water in a sol?
What is the Tyndall phenomenon?
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What is the main difference between colloids and true solutions?
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What happens when a beam of light is passed through a true solution?
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What is the basis of the development of the ultra-microscope?
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What is the term for the conversion of a gel to a sol by heating?
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What is the state of water in a gel?
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Who discovered the Tyndall phenomenon?
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Study Notes
Types of Colloids
- Whipped cream, soap, and lather are examples of foams, where gas is dispersed in a liquid.
- Pumice stone and rubber are examples of solid foams, where gas is dispersed in a solid.
Classification of Colloids
- Lyophobic colloids have no affinity between dispersed particles and the dispersion medium.
- Lyophilic colloids have a great affinity between dispersed particles and the dispersion medium.
Properties of Colloids
- Particle size: Colloids have particles between 0.1 µ and 0.001 µ in size.
- Visibility of particles: Colloids are invisible to the naked eye, but visible under a powerful microscope.
- Sedimentation of particles: Colloids do not settle down, but may settle under high centrifugation.
- Filtration through filter paper: No residue is formed.
Methods of Formation of Colloids
- Condensation (Association) method: Small particles collect until they reach colloidal size.
- Dispersion (Dissociation) method: Coarse particles are broken down until they reach colloidal size.
Types of Colloids
- 8 types of colloids exist, depending on the state of the dispersed particles and the dispersion medium.
Hydrophilic Sol Colloids
- Hydrophilic sol colloids have the property of setting into a rigid and elastic gel under changing conditions.
Gelation and Solation
- Gelation: The conversion of a sol to a gel by cooling.
- Solation: The conversion of a gel to a sol by heating.
Properties of Sol and Gel
- Sol: Most of the dispersion medium is in the free state, separating the gelatin particles.
- Gel: Much water is present, but is not easily withdrawn, and few molecules of water are free.
Tyndall Phenomenon
- Tyndall phenomenon: Scattering of light by colloidal particles, discovered by John Tyndall.
- The development of the ultra-microscope is based on the scattering of light by colloidal particles.
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Description
This quiz covers the types of colloids, including foams, solid foams, and more, with examples of each. Test your knowledge of dispersed phases and dispersion mediums!
