Railway Science (Chemistry-Solutions)

Sublimation is the conversion of the solid into the gaseous state, with no intermediate liquid stage. Examples - Camphor, Iodine, dry ice (Solid CO₂). The process of conversion of liquid into a gas is called Vapourisation.

Solution is a homogeneous mixture of two or more substances depending on whether the solvent is water or not. Aqueous solution (aq) - When a solute is dissolved in water. Example - Salt water, sugar water.
Concentrated solution contains a relatively large amount of solute dissolved in a given amount of solvent.
Isotonic solution is one in which the concentration of solutes is the same as that of another solution or the interior of a cell.

Properties of a Suspension - It is a heterogeneous mixture. The particles of a suspension can be seen by the naked eye. Its particles scatter a beam of light passing through it and make its path visible.Colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance.
Unsaturated solution is a solution in which the solvent has dissolved less solute than it is capable of dissolving at a given temperature and pressure. Saturated solution is a solution that has dissolved as much solute as it is capable of dissolving.

Evaporation - It is the process by which a liquid turns into a gas. Example - Hot tea getting cold, Wet clothes drying, Salt formation. Diffusion is free intermixing of molecules of different substances where no semi-permeable membrane is required while in osmosis only solvent particles can diffuse and a semipermeable membrane is required.

Evaporation - A type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. Sublimation - The transition of a substance from the solid phase to the gaseous phase without changing into the liquid phase. Centrifugation - A system that separates the component parts of a liquid or fluid using centrifugal force. Filtration - The process of separating suspended solid matter from a liquid.

True Solution: A homogenous mixture. Example - salt solution. Colloidal solution: The size of solute particles is between 10⁻⁹ m to 10⁻⁶ m. Example - Milk, Blood.  Suspension: Size of particles bigger than 10⁻⁶ m. Example - Mud in water.

Solubility - The ability of a solute to dissolve in a solvent to form a solution. Example - Salt (sodium chloride) in water, Oil paint and thinner. Viscosity is a measure of the resistive flow of a fluid under the influence of gravity.
It describes the internal friction of a moving fluid. Honey, mostly glucose and fructose is an example of a liquid which owes its viscosity to hydrogen bonding.

Immiscible Liquids: It does not mix with each other and form a heterogeneous mixture. It is due to difference in the density of liquids. The denser liquid stays at bottom and lighter stays on top forming separate layers. Example - Petrol and water.
Miscible liquids - It forms a homogeneous mixture. Example - Alcohol and water. Sublimation - Conversion of substance from solid phase to gaseous state without converting into liquid. Example - Salt and camphor separated by sublimation. Chromatography - Used to separate dye from black ink.

Milk - It is a colloidal solution. The scattering of light by the colloid particles is known as the tyndall effect. It shows that the colloidal particles are much bigger than the particles of a true solution and smaller than particles in suspensions. Other example - Starch solution.

Colloids : A mixture where at least two types of substances are placed together. Examples - Whipped cream, Mayonnaise, milk, butter gelatin, paper. Types of Colloids : Sol - Dispersed Phase (Solid), Dispersion Medium (Liquid), Examples - Gold sol, sulfur sol .
Emulsion - Dispersed Phase (Liquid), Dispersion Medium (Liquid), Examples - Milk, cream, mayonnaise. Foam - Dispersed Phase (Gas), Dispersion Medium (Liquid), Examples - Whipped cream, soap Lather. Aerosol - Dispersed Phase (Liquid or Solid), Dispersion Medium (Gas), Examples - Cloud, mist, fog.