Railway Science (Chemistry-Metals , Non-Metals and Alloys) (Part-II)

Aluminothermic reactions are high-temperature exothermic chemical processes. This procedure is used to make Ferrous alloys in the industry. Reducing agents reduces others while itself gets oxidized by losing electrons. An oxidizing agent is a substance that causes oxidation by accepting electrons. Hydrogenation - A chemical reaction between molecular hydrogen (H₂) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum.

Calcium has a density of 1.55 g/cm³ which is more than water. The density of water is the weight of the water per its unit volume. Density of water - 1g/cm³ . All metals on the periodic table are denser than water except - Lithium - 0.534 g/cm³ , Potassium - 0.862 g/cm³and Sodium - 0.971 g/cm³ . Objects which are less dense than water will float on it while the denser objects will sink in water.

Total distance from an atom's nucleus to the outermost shell containing electrons. Due to the addition of electrons to the same shell in all atoms, the atomic radius decreases on moving from left to right across the period and increases on going top to bottom across groups in a periodic table. Group 1A (or IA) of the periodic table are the Alkali metals: Hydrogen (H), Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs), and Francium (Fr).

These elements are characterized by having intermediate properties of metals and non-metal. Examples: Boron (B), Silicon (Si), Germanium (Ge). Tellurium (Te, atomic number - 52) is a brittle, mildly toxic, rare, silver-white metalloid. Metals are good conductors of heat and electricity, and are malleable. Example: Gold (Au), Silver (Ag), Iron (Fe). Non-metals are (usually) poor conductors of heat and electricity, and are not malleable or ductile. Example: Oxygen (O), Nitrogen (N), Carbon (C).

Metal - An element that can easily form positive ions called cations and tends to make metallic bonds. Examples of metals are gold, aluminum, iron and magnesium etc. Physical Properties of Metals: Malleability, ductile, good conductor of heat and electricity. A non metal - A chemical element that generally in a chemical reaction gains electrons when reacts with a metal. Examples: Chlorine, carbon, bromine, sulphur, phosphorus.

Example - Iron (Fe), Copper (Cu). Mixtures - a physical blend of two or more substances in which identities are retained and are blended in the form of solutions, suspensions, or colloids. Example - Smog, Blood. Compounds - substance formed when two or more chemical elements are chemically bonded together. Example - Water. A pure substance - A substance in which all the particles present are of the same chemical nature.

Zinc Amalgam is an alloy of Zinc (Zn) and Mercury (Hg). Alloys of mercury are called Amalgam. Alnico - magnetic alloy of Aluminium (Al), Cobalt (Co), Nickel (Ni) and some amount of copper (Cu). Solder - Fusible metal alloy made up Lead (Pb) and Tin (Sn). Stainless steel - Corrosion-resistant alloy of Iron (Fe), chromium (Cr) and Nickel (Ni).

Metalloids are elements that have properties of both metals and non - metals. They have intermediate properties of electrical conductivity, thermal conductivity, and reactivity.
Silicon (Si): Atomic Number = 14. It is a hard and brittle solid, which makes it a typical characteristic of a non-metal. It also conducts electricity and has a metallic luster, which makes it similar to a metal. It forms acidic oxides like SiO₂ (silicon dioxide) and covalent halides like SiCl₄ (silicon tetrachloride), which are typical properties of a non-metal.

(symbol - Hg, liquid at room temperature). Thermal conductivity - the rate at which heat is transferred by conduction through a unit cross-section area of a material, when a temperature gradient exists perpendicular to the area. Diamond (hardest allotrope of carbon) It has high thermal conductivity. with conductivity levels 5 times better than copper.

Atomic number 13 Discovered by Hans Oersted in 1825. Chemical Reaction: 2 Al + 3 H₂O → Al₂O₃ + 3 H₂ . Some metals which react with steam:- Magnesium: Mg + 2H₂O → Mg(OH)₂ + H₂ , Zinc: Zn + H₂O → ZnO + H₂ , Iron: 3 Fe + 4 H₂O → Fe₃O₄ + 4H₂ .