Railway Science (Chemistry-Solutions)

Brine is used for food processing and cooking (pickling and brining), for de-icing of roads and other structures and in a number of technological processes. Sodium Chloride (Common salt - NaCl). Caustic Soda (Sodium Hydroxide - NaOH). Limestone (Calcium carbonate - CaCO₃). Quicklime (Calcium oxide - CaO).

They are mixtures in which microscopically dispersed insoluble particles of one substance are suspended in another substance. The size of the suspended particles in a colloid can range from 1 to 1000 nanometres (10⁻⁹ meters).
Salt is the outcome of a neutralization reaction. Water is a compound of Hydrogen and Oxygen (H₂O). Sugar is the generic name for sweet-tasting, soluble carbohydrates.

Ammonia (NH₃) - It is a colorless highly irritating gas with a sharp suffocating odor. It dissolves easily in water to form ammonium hydroxide (NH₄OH) solution which can cause irritation and burns. About 80% of the ammonia produced by industry is used in agriculture as fertilizer.
It is also used as a refrigerant gas, for purification of water supplies, and in the manufacture of plastics, explosives, textiles, pesticides, dyes and other chemicals.

Solution - In a solution, one substance (called the solute) is dissolved uniformly in another substance (called the solvent). Example - Carbonated beverages. Homogeneous mixture - The composition is uniform throughout the mixture. Example - Air.
Molecule - smallest unit of a chemical compound that retains the chemical properties of that compound. It is made up of two or more atoms chemically bonded together. Example - H₂O (water).

Aluminum hydroxide - It has both basic and acidic properties, therefore it is called amphoteric. Alkaline solution - A solution of a soluble base with a pH greater than 7. Example - Sodium hydroxide (NaOH), Magnesium hydroxide (Mg(OH)₂O), Calcium hydroxide (Ca(OH)₂), Potassium hydroxide (KOH). Nature of compounds according to pH value : Acidic (pH value 0 to less than 7), Neutral (pH value 7).

Tyndall effect - Colloids can scatter a beam of light passing through them. Colloidal solution (Colloidal suspension) - A type of mixture in which tiny particles or droplets are dispersed and suspended within a continuous medium. Examples - Whipped cream, mayonnaise, milk, butter, Gelatin, Jelly, Muddy water, plaster, colored glass, and paper.

Electrolyte - A substance that conducts electricity when dissolved in water or molten state, and dissociates into ions.
Suspension - A heterogeneous mixture in which solid particles are dispersed in a liquid or gas, but are not completely dissolved and may settle over time.
Emulsion - A mixture of two immiscible liquids, such as oil and water, where one liquid is dispersed as small droplets in the other.

Diffusion: Due to it the smell of perfume reaches our nose quickly. Condensation - Process through which physical state of matter changes from gas to liquid. Example - Morning dew on the grass, Foggy car windows.

The factors affecting evaporation (liquid changes into a vapor or gaseous state) are wind speed (rate of evaporation is directly proportional to the wind speed), level of humidity (When there is high humidity, the rate of evaporation slows down because vapors are already present in the air), temperature (direct relationship between temperature and the rate of evaporation), surface area (greater the surface area, the higher the rate of evaporation), and the nature of the liquid.

When water reaches above the boiling point (100o C), it slowly changes into a gaseous state. It occurs in solid state below its freezing point (0o C). In between freezing point and boiling point water is present in liquid state.
Solids: Molecules are closely bound to one another by molecular forces. Examples - Iron, brick, coin.
Liquids: Molecular forces are weaker than solid. Examples - Juice, energy drinks, cold drinks.
Gas - Molecular forces are very weak. Examples - Natural gas, oxygen, carbon dioxide. Plasma is the liquid portion of blood. It helps in blood clotting.