General Science Compendium
2. Isotopes are any of the different types of atoms of the same chemical element, each having a different atomic mass (mass number).They have same number of protons (the same atomic number) but different numbers of neutrons. Carbon-12 & carbon-13 is an example of Isotopes
3. Allotropy is related to two or more different forms of a particular element. In each allotrope, the element’s atoms are bonded together in a different manner. Carbon, Graphite & Diamonds are allotropes. please note that changes of state between solid, liquid and gas in themselves are not considered allotropy.so Ice & water are not allotropes.
4. Calcium hypochlorite is a chemical compound with formula Ca(ClO)2. It is widely used for water treatment and as a bleaching agent (bleaching powder).
5. Annealing is a process of slowly cooling glass to relieve internal stresses after it was formed. The process may be carried out in a temperature-controlled kiln known as a Lehr.It is done to avoid the glass article becoming brittle or opaque.
6. Inertia is the resistance of mass, i.e. any physical object, to a change in its state of motion. Newton’s First Law is based upon this.
1. In the absence of net external force, a body either is at rest or moves in a straight line with constant velocity.
2. Force is proportional to mass times acceleration (when proper units are chosen, F = ma). Alternatively, force is proportional to the time rate of change of momentum.
3. Whenever a first body exerts a force F on a second body, the second body exerts a force −F on the first body. F and −F are equal in size and opposite in direction.
7. Fluorine is powerful oxidizing agent. It is the most reactive and most electronegative of all the elements on the Pauling scale (4.0), and readily forms compounds with most other elements. It has an oxidation number -1, except when bonded to another fluorine in F2 which gives it an oxidation number of 0.
Some Other memorable Points:
The carbon–fluorine bond is one of the strongest bonds in organic chemistry. This contributes to the stability and persistence of fluoroalkane based organofluorine compounds, such as PTFE/(Teflon) and PFOS. The carbon–fluorine bond’s inductive effects result in the strength of many fluorinated acids, such as triflic acid and trifluoroacetic acid.
8. The maximum density of water occurs at 3.98 °C. Water becomes even less dense upon freezing, expanding 9%. This is also a reason behind the survival of organism below ice layers in water bodies. Ice floats upon the water body and water on the bottom has a temperature of around 4 °C.
9. The Story of Three calcium Compounds:
Calcium oxide is Quick Lime and is is usually made by the thermal decomposition limestone Calcium Carbonate in a kiln.
CaCO3 ———> CaO + CO2
Slacked Lime is Calcium Hydroxide Ca(OH)2 which is produced by reaction of Quick Lime CaO with Water. The reaction produces energy .
CaO + H2O =Ca(OH)2 (ΔHr = -63.7 kJ/mol of CaO)
10. Rayon is a manufactured regenerated cellulose fiber. Because it is produced from naturally occurring polymers (Cellulose) , it is neither a truly synthetic fiber nor a natural fiber, it is a semi-synthetic fiber.Rayon is a very versatile fiber and has the same comfort properties as natural fibers. It can imitate the feel and texture of silk, wool, cotton and linen.
11. Examples of Thermosetting Plastics:
Polyester fiberglass systems, Vulcanized rubber, Bakelite,Duroplast, Melamin, Epoxy resin, Polyimides & Mold
Examples of Thermoplastics: Polyethylene, PVC, PolyPropylene.
12. glass coloring agents:
Iron(II) : Brown or bluish Green
Cadmium Sulphide:Deep Yellow
Cobalt oxide : Blue
Chromium oxide : Green
Manganese dioxide : Purple
Copper oxide : Red / turquoise