Grade 12
  1. Solid state  1.1. Classification of solids  1.2. Crystal Lattice and Unit Cell  1.3. Packing Efficiency  1.4. Density of unit cell  1.5. Imperfections in solids (point and line defects)  1.6. Electrical Properties of Solids (Conductors, Insulators and Semiconductors)  1.7. Magnetic Properties of Solids (Diamagnetic, Paramagnetic and Ferromagnetic Materials)
  2. Solution  2.1. Types of Solutions (Homogeneous and Heterogeneous)  2.2. Expressing concentration of solutions (mass %, volume %, molarity, molality, normality, mole fraction)  2.3. Solubility of solids and gases in liquids (Henry's law)  2.4. Raoult's Law and Ideal and Non-Ideal Solutions  2.5. Syndrome properties  2.6. Abnormal molar mass and Van't Hoff factor
  3. Electrochemistry  3.1. Electrochemical cells (galvanic and electrolytic cells)  3.2. Galvanic cell and EMF of the cell  3.3. Standard electrode potential and electrochemical series  3.4. Nernst equation and its applications  3.5. Conductivity and electrolytic cells (specific, molar and equivalent conductivity)  3.6. Kohlrausch's law and its applications  3.7. Batteries (primary and secondary cells)  3.8. Corrosion and its prevention
  4. Chemical kinetics  4.1. Rate of chemical reaction  4.2. Factors affecting the reaction rate (concentration, temperature, catalyst, surface area)  4.3. Order and molecularity of the reaction  4.4. Integrated Rate Equations (Zero, First and Second Order)  4.5. Half-life of a reaction  4.6. Collision theory and activation energy  4.7. Arrhenius equation and its applications
  5. Surface chemistry  5.1. Adsorption and its types (Physicosorption and Chemisorption)  5.2. Catalysis and its types (homogeneous and heterogeneous)  5.3. Colloids and their properties (Tyndall effect, Brownian motion, coagulation)  5.4. Emulsions and gels  5.5. Applications of Colloids
  6. General principles and processes of separation of elements  6.1. Presence of metals and minerals  6.2. Concentration of ores (gravity separation, froth flotation, magnetic separation)  6.3. Extraction of raw metals (roasting, calcination, reduction)  6.4. Thermodynamic and electrochemical principles of metallurgy  6.5. Refining of metals
  7. P-block elements  7.1. Group 15 elements (nitrogen and phosphorus)  7.2. Group 16 Elements (Oxygen, Sulphur and their Compounds)  7.3. Group 17 Elements (Halogens and their Compounds)  7.4. Group 18 Elements  7.5. Properties and Trends in p-Block Elements  7.6. Important compounds of p-block elements (ammonia, phosphine, sulphuric acid, hydrochloric acid)  7.7. Interhalogen compounds and their applications
  8. d-block and f-block elements  8.1. General Properties of Transition Metals  8.2. Properties of Inner Transition Metals (Lanthanoids and Actinoids)  8.3. Lanthanoid and actinoid contractions  8.4. Coordination Chemistry of d-Block Elements
  9. Coordination compounds  9.1. Werner's theory and modern concepts  9.2. Coordination number and type of ligand  9.3. Nomenclature of Coordination Compounds  9.4. Isomerism (geometrical and optical) in coordination compounds  9.5. Bonding in Coordination Compounds (Valence Bond Theory and Crystal Field Theory)  9.6. Stability and applications of coordination compounds in medicine and industry
  10. Haloalkanes and haloarenes  10.1. Classification and nomenclature of haloalkanes and haloarenes  10.2. Physical and Chemical Properties of Haloalkanes and Haloarenes  10.3. Mechanism of Nucleophilic Substitution Reactions (SN1 and SN2)  10.4. Uses and environmental effects (ozone depletion, CFCs)
  11. Alcohol, phenol and ether  11.1. Structure and classification of alcohols, phenols and ethers  11.2. Preparation and properties of alcohols  11.3. Preparation and properties of phenol  11.4. Preparation and properties of ethers  11.5. Chemical Reactions and Uses
  12. Aldehydes, ketones and carboxylic acids  12.1. Structure and nomenclature in aldehydes, ketones and carboxylic acids  12.2. Preparation and properties of aldehydes and ketones  12.3. Chemical reactions in aldehydes, ketones and carboxylic acids (nucleophilic addition, oxidation and reduction)  12.4. Preparation and Properties of Carboxylic Acids  12.5. Chemical Reactions and Uses of Carboxylic Acids
  13. Nitrogen-containing organic compounds  13.1. Amines (classification, structure, basicity)  13.2. Preparation and properties of amines  13.3. Reactions of Amines (Diazotization, Carbylamine Reaction)  13.4. Diazonium salts and their applications in paint industry
  14.1. Carbohydrates (classification and properties)  14.2. Proteins (Structure and Function)  14.3. Enzymes (Mechanism and Function)  14.4. Nucleic acids (DNA and RNA)  14.5. Vitamins and hormones
  15. Polymer  15.1. Classification of Polymers (Addition, Condensation, Copolymers)  15.2. Types of polymerization (free radical, ionic, condensation)  15.3. Important Polymers and Their Uses  15.4. Biodegradable and non-biodegradable polymers
  16. Chemistry in Everyday Life  16.1. Drugs and their classification (analgesics, antipyretics, antibiotics, antacids)  16.2. Chemicals in food and cosmetics (preservatives, artificial sweeteners, antioxidants)  16.3. Cleaning agents and detergents (soaps, synthetic detergents, surfactants)  16.4. Environmental Chemistry (Pollution, Green Chemistry, Sustainable Chemistry)

Grade 12 → Surface chemistry ↓


Colloids and their properties (Tyndall effect, Brownian motion, coagulation)


A colloid is a mixture of finely dispersed insoluble particles suspended in another substance. Some colloids are translucent due to the Tyndall effect, which is the scattering of light by particles in a colloid.

Understanding colloids

Colloids are unique states of matter because they are different from solutions or mere suspensions. These mixtures have particles that are evenly dispersed but large enough to scatter light, yet small enough to not settle under gravity.

An everyday example of a colloid is milk, where droplets of fat are dispersed in water. Other examples include fog, jelly, and smoke.

Types of colloids

Colloids can be classified based on the state of the dispersed phase and the dispersion medium.

  • Sol: Solid particles in a liquid. Example: paint.
  • Gel: Liquid dispersed in a solid. Example: cottage cheese, agar.
  • Aerosol: Liquid or solid particles in a gas. Example: fog, smoke.
  • Emulsion: Liquid particles in another liquid. Examples: milk, mayonnaise.
  • Foam: Gas particles in a liquid or solid. Examples: whipped cream, marshmallows.

Tyndall effect

The Tyndall effect is a phenomenon in which light is scattered by particles in a colloid. This scattering is visible when a beam of light passes through a colloidal solution.

Scattering of light due to colloidal particles

This effect is similar to what happens when you look at a beam of sunlight passing through fog or smoke, allowing you to see the beam visually. This property helps distinguish colloids from true solutions; in solutions, the path of light will not be visible because the particles are too small to scatter the light.

Brownian movement

Brownian movement, named after botanist Robert Brown, is the irregular, random motion of colloidal particles suspended in a fluid. This motion is caused by collisions with faster-moving molecules of the surrounding medium.

This phenomenon can be observed under a microscope, where tiny pollen particles dance around randomly in water. The scattered particles move and wiggle around due to the constant bombardment of solvent molecules.

Random motion of particles due to molecular collisions

Brownian motion prevents colloidal particles from settling down, which helps maintain the stability of the colloid. This also provides further evidence of the particulate nature of matter.

Coagulation

Coagulation or flocculation is the process in which colloidal particles come together to form larger clumps. As a result, the colloidal particles settle out of the dispersion medium.

Coagulation methods

Deposition can occur in several ways:

  • Adding electrolytes: Adding electrolytes reduces the repulsion between the particles. This causes the particles to come together and form clusters and eventually freeze.
  • Mixing two oppositely charged sols: When positively charged sols and negatively charged sols are mixed, they neutralise each other's charge, leading to coagulation.
  • Boiling: Heat slows down the movement of particles, leading to coagulation.
  • By continuous dialysis: Long-term dialysis removes the absorbed stable electrolytes, causing the particles to clump together.

Coagulation is used in water treatment to remove suspended impurities. It is also an important process in the manufacture of some materials where purity and stability are important.

Aggregated particles after deposition

Examples and applications of colloids

The properties of colloids make them extremely useful in a variety of applications:

  • Medicine: Colloidal silver and gold are used due to their antimicrobial properties.
  • Food industry: Emulsions such as mayonnaise and cream are used in food production.
  • Agriculture: Pesticide sprays are colloids.
  • Industry: Paints, inks, and glues are colloidal substances often used in manufacturing.

Colloids are a fascinating and complex area of chemistry, where understanding these small-scale interactions has wide-ranging applications in many fields. The study of colloids not only deepens our understanding of chemical processes, but also demonstrates the complex balance and behavior of tiny particles in everyday matter.


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Colloids and their properties (Tyndall effect, Brownian motion, coagulation)

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