Chemistry Test - 4

As a general rule, fluorine is the most reactive halogen and astatine is the least reactive. All halogens form Group 1 salts with similar properties.

Esters are common in organic chemistry and biological materials, and often have a characteristic pleasant, fruity odour. This leads to their extensive use in the fragrance and flavor industry. Ester bonds are also found in many polymers. Esterification is the general name for a chemical reaction in which two reactants (typically an alcohol and an acid) form an ester as the reaction product. Esters are widespread in nature and are widely used in industry.

Nichrome is a non-magnetic alloy of nickel, chromium, and often iron, usually used as a resistance wire. Patented in 1905, it is the oldest documented form of resistance heating alloy. A common alloy is 80% nickel and 20% chromium, by mass, but there are many others to accommodate various applications. It is silvery-grey in colour, is corrosion-resistant, and has a high melting point of about 1400 degree C (2552 degree F).

A greenhouse gas (sometimes abbreviated GHG) is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth 's atmosphere are water vapour, carbon dioxide, methane, nitrous oxide, and ozone. In the Solar System, the atmospheres of Venus, Mars, and Titan also contain gases that cause greenhouse effects.

Pasteurization for pasteurisation) is a process of heating a food, which is usually a liquid, to a specific temperature for a predefined length of time and then immediately cooling it after it is removed from the heat. This process slows spoilage due to microbial growth in the food. Unlike sterilization, pasteurization is not intended to kill all micro organisms in the food. Instead, it aims to reduce the number of viable pathogens so they are unlikely to cause disease (assuming the pasteurized product is stored as indicated and is consumed before its expiration date).

The atmosphere of Earth is a layer of gases surrounding the planet. Earth that is retained by Earth 's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night. Air is the name given to the atmosphere used in breathing and photosynthesis. Dry air contains roughly (by volume) 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases.

Steel is an alloy made by combining iron and other elements, the most common of these being carbon. When carbon is used, its content in the steel is between 0.2% and 2.1% by weight, depending on the grade. Other alloying elements sometimes used are manganese, chromium, vanadium and tungsten. Carbon and other elements act as a hardening agent, preventing dislocations in the iron atom crystal lattice from sliding past one another.

Cloud seeding, a form of intentional weather modification, is the attempt to change the amount or type of precipitation that falls from clouds, by dispersing substances into the air that serve as cloud condensation or ice nuclei, which alter the rnicrophysical processes within the cloud. The usual intent is to increase precipitation (rain or snow), but hail and fog suppression are also widely practiced in airports. The most common chemicals used for cloud seeding include silver iodide and dry ice (solid carbon dioxide).

Dichlorodifluorornethane (R-12), is a colourless gas, and usually sold under the brand name Freon-12, is a chlorofluorocarbon halornethane (CFC), used as a refrigrant and aerosol spray propellant. Complying with the Montreal Protocol, its manufacture was banned in the United States along with many other countries in 1994 clue to concerns about damage to the ozone layer. It is soluble in many organic solvents.

All the elements have the same number of shells. Therefore, if an element is present in the 3rd period, it has  3 shells .

A bullet-proof material is made of polyethylene. It is a higher grade of the plastic found in Tupperware.

The atomic nucleus consists of nucleons —protons and neutrons. Protons and neutrons are made of quarks and held together by the strong force generated by gluon exchange between quarks.

Uranium is a chemical element with symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table.

Explanation: A battery is a form of chemical energy that can be converted to electrical energy. it is a device consisting of one or more electrochemical cells which performs this action. The first battery (or "voltaic pile ") was invented in 1800 by Alessandro Volta.

Nuclear power is now used in all large submarines, but due to the high cost and large size of nuclear reactors, smaller submarines still use diesel-electric propulsion. The ratio of larger to smaller submarines depends on strategic needs. The US Navy, drench Navy, and the British Royal Navy operate only nuclear submarines.

When baking soda and lemon juice are added together, the reaction of the two is an acid-based reaction because it involves an acid (citric acid in the lemon juice) reacting with a base (sodium bicarbonate, more commonly known as baking soda). Carbon dioxide, a gas, is produced by the reaction.

Fertilizers typically provide, in varying proportions: (1) six macronutrients: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S); and (ii) eight micronutrients: boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), zinc (Zn) and nickel {Ni}.

Gold plating is a method of depositing a thin layer of gold onto the surface of another metal, most often copper or silver (to make silver-gilt), by chemical or electrochemical plating. Electroplating of gold is done using a sulphate/sulfite based electrolyte. This product is environment and user friendly and moreover the electroplating rate is good.

Isoprene was first isolated by thermal decomposition of natural rubber. About 95% of isoprene production is used to produce cis-1,4- polyisoprene---a synthetic version of natural rubber. Natural rubber consists mainly of poly-cis isoprene with a molecular weight of 100,000 to 1,000,000.

Polystyrene is an synthetic aromatic polymer made from the monomer styrene, a liquid petrochemical. It is one of the most widely used plastics. Uses include protective packaging (such as packing peanuts and CD and DVD cases), containers (such as "clamshells "), lids, bottles, trays, tumblers, and disposable cutlery.