Railway Science (Chemistry-Chemical Properties)

Oxidation - It is defined as the addition of oxygen to the substance or the removal of hydrogen from the substance. The given reaction - 4Fe(s) + 3O₂(g) → 2Fe₂O₃(s).
Iron oxide (rust) is created when iron and air interact in the presence of water or air moisture. Iron is oxidized in this reaction by the addition of oxygen. Iron (Fe) - Atomic Number - 26, Atomic Mass - 55.85.

Ca(OH)₂ , or slaked lime or hydrated lime - A soft white powder. Use - As a raw material in the chemical industry. Calcium carbide (CaC₂), or calcium acetylide.
Use - In the production of acetylene and calcium cyanamide. Calcium oxide (CaO), or quicklime or burnt lime - A white, caustic, alkaline, crystalline solid at room temperature.

Test tube (A) contains a starch solution, so when dilute iodine solution is added to it, a blue-black color is seen. Test tube (B) contains a starch solution and saliva. Saliva contains the enzyme salivary amylase which breaks down starch into simple sugars. Iodine cannot form a complex with sugars, hence no blue-black color is seen in the test tube (B).

Coal tar is a mixture of different carbon compounds. It is a thick, black liquid with an unpleasant smell. The fractional distillation of coal tar gives many chemical substances.
Uses: dyes, explosives, paints, synthetics fibers, drugs, and pesticides. Naphthalene is an aromatic hydrocarbon found in coal tar or crude oil. Naphthalene Uses - Manufacture of plastics, resins, fuels, and dyes.

When an iron nail is dipped in copper sulphate solution originally in blue colour, the surface of the iron develops a brown copper coating and the colour of the copper sulphate solution changes from blue to pale green. CuSO₄(Copper Sulphate) + Fe(Iron) → FeSO₄(Iron Sulphate) + Cu (Copper). Metal that comes first in the reactivity series will replace metals that come after it.
Reactivity series - Potassium (K) > Sodium (Na) > Calcium (Ca) > Magnesium (Mg) > Aluminium (Al) > Zinc (Zn) > Iron (Fe) > Lead (Pb) > Hydrogen (H) > Copper (Cu) > Mercury (Hg) > Silver (Ag) > Gold (Au).

CaCl₂ (Calcium Chloride) - White-coloured crystalline solid at room temperature, and highly soluble in water. Formation - by neutralising hydrochloric acid with calcium hydroxide.
Ionic compounds are formed by the transfer of an electron between two atoms. Thus the formation of the cation and anion takes place. Due to very strong electrostatic forces of attraction between cations and anions, these possess very high boiling/melting points.

Aqueous solution of sodium chloride conducts electricity because it is a soluble ionic compound, which when dissolved in water, dissociates into Na+ and Cl- and these ions conduct electricity.
Glucose and alcohol does not conduct electricity in its aqueous solution state. They do not dissociate in aqueous solution and no current carrying ions are produced.

Common name - Washing soda; Uses - In the manufacture of detergents, soaps, paper, water glass (sodium silicate), borax, sodium phosphate, and many other sodium compounds.

Cement. Limestone - It is a sedimentary rock made of calcium carbonate (CaCO₃). It is used extensively in road and building construction, and is a material found in cement, building stones, chalk, and crushed stone.

Uses:- To make sculptures and metal castings used as decorative in buildings.