Fact to remember
Name of the gas
Gas most abundant in earth's atmosphere
Percentage of oxygen in earth's atmosphere
The lightest gas
The heaviest gas
Nitrous Oxide (N2O)
Mainly methane with small quantities of ethane and propane
Methane, CO2 and hydrogen
Gas with foul smell
Hydrogen Sulphide (H2S)
Gas mixed with oxygen and given to patients with restricted breathing
A major air pollutant, the percentage presence of which is checked in vehicle pollution test
The gas which is responsible for the formation of brown air in traffic congested cities
Major gaseous pollutant of areas located near thermal power station
Strong smelling substance added to LPG
Ethyl Mercaptan or Ethanethiol
Gases responsible for depletion of ozone layer
Gas responsible for acid rain
Gas used in gas welding and also artificial ripening of fruits
Gas used in electric bulbs
Gas used in flourescent lamps
Gas used in LPG
Butane, Propane and Ethane
Gas used in refrigeration
Freon (Diflouro Dichloro Methane)
Gas used as an anaesthetic in dental surgery
The metal with the highest melting point is Tungsten.
The metal with the highest thermal conductivity is Silver.
The metal with the highest electrical conductivity is Silver.
The metal with the highest density is Osmium.
The metal with the lowest density is Lithium.
The most malleable and ductile metal is Gold.
The least reactive metal is Platinum.
Metal most abundant in earth’s crust is Aluminium.
Metal which forms amalgam with other elements is Mercury.
Metal used in a fuse wire and also in solder - Lead-tin alloy.
Metal used in the filament of a bulb is Tungsten.
Metal which pollutes the air of cities having large number of vehicles is Lead (reason for using unleaded petrol)
Metal used in the filaments of electric heaters - Nichrome.
Metal used as radiation shield is Lead.
Metal into which Uranium turns when it loses all its radioactivity is Lead.
Metal used for making boats because it does not corrode by seawater is Titanium.
Aluminium and Copper
Copper and Zinc
Copper and Tin
Iron and Nickel
Iron, Chromium and Nickel
Copper, Nickel and Zinc
Copper, Tin and Zinc
Lead and Tin
Gold and Silver
Copper and Nickel
Copper, Manganese and Nickel
Manganin is a trademarked name.
Ores of Metals
It is a process in which a metal is heated to a specific temperature and then cooled slowly in order to make the metal soft enough for easy cutting and shaping.
It is a process in which a metal is heated to a specific temperature and then cooled suddenly in order to make the metal hard. This also makes the metal brittle or easy to break.
It is a process in which a hardened metal is heated to a specific temperature and then cooled slowly in order to make the metal tough enough for use as cutting or abrading tool. Tools such as drills, chisels, files etc. are hardened and tempered.
It is a process in which a protective zinc coating is applied on iron to prevent it from rusting.
It is process for joining similar metals by melting and fusing the base metals as well as the filler metal. Welding is usually used with ferrous-based metals such as steel and stainless steel. The temperature range of welding is 800ºC - 1635ºC. Welded joints are the strongest of joints.
It is a process in which two close-fitting parts are joined by using a filler material which is heated above its melting point and distributed in the gap by capillary action. A chemical cleaning agent known as flux is used to prevent oxidation of metals being heated. Temperature range for brazing is above 450ºC.
It is a process similar to brazing but the filler material is of much lower melting point. The filler material, solder is an alloy of tin and lead. Temperature range for soldering is below 450ºC. Soldered joints are the weakest of the three viz welding, brazing and soldering.
It is process in electric current is used to deposit ions of a metal on another. Thus chromium may be used to plate iron bars. Electroplating is usually done to prevent corrosion of the base metal or for decorative purpose.
It is a process of extracting a metal from its ore by heating the ore beyond its melting point. Flux is used in the process to remove the slag.
It states that equal volumes of gases at the same temperature and pressure contain the same number of molecules regardless of their chemical nature and physical properties. This number (Avogadro's number) is
6.022 X 1023. It is the number of molecules of any gas present in a volume of 22.41 litres and is the same for the lightest gas (hydrogen) as for a heavy gas such as carbon dioxide or bromine.
Stated in 1811 by the Italian chemist Amedeo Avogadro (1776-1856)
For a fixed amount of an ideal gas kept at a fixed temperature, P [pressure] and V [volume] are inversely proportional (while one doubles, the other halves). In other words product of the pressure and volume is exactly a constant for an ideal gas.
Propounded by Robert Boyle, an Irish Chemist in 1662
It states that the volume of a gas is directly proportional to the temperature of the gas, provided the amount of gas and pressure are held constant.
It was first published by French natural philosopher Joseph Louis Gay-Lussac in 1802, giving credit to an unpublished work from the 1780s by Jacques Charles. It is also known as Gay-Lussac Law.
The magnitude of the Electrostatics force of interaction between two point charges is directly proportional to the scalar multiplication of the magnitudes of charges and inversely proportional to the square of the distances between them.
Published in 1783 by French physicist Charles Augustin de Coulomb.
The induced electromotive force (EMF) in any closed circuit is equal to the time rate of change of the magnetic flux through the circuit.
Published by English Physicist Michael Faraday in 1831.
It states that, for relatively small deformations of an object, the displacement or size of the deformation is directly proportional to the deforming force or load.
Discovered by the English scientist Robert Hooke in 1660.
It states that, heat produced by an electric current is directly proportional to the resistance of the conductor, the square of the current, and the time for which it flows.
Given by the English physicist James Prescott Joule around 1850.
Unit of Measurement
Amount of Substance
Unit of Measurement
Magnetic Flux Density
Instruments and their uses
Bolometer - Instrument for measuring radiation by means of the rise in temperature.
Hydrometer - Instrument for measuring the density of liquids.
Hygrometer - Instrument for measuring the humidity of the air or a gas
Lactometer - Instrument for measuring the amount of water in milk
Anemometer - Instrument for measuring wind force.
Salinometer - Instrument for measuring the salinity of a solution
Altimeter - Instrument for measuring the altitude of an aircraft etc.
Galvanometer - Instrument for detecting and measuring electric currents
Telescope - Optical instrument using lenses or mirrors to magnify distant objects.
Microscope - Instrument with lenses for magnifying objects or details invisible to the naked eye.
Stethoscope - Instrument used in listening to the heart, lungs, etc. [Greek stethos breast]
Kaleidoscope - Tube containing mirrors and pieces of coloured glass etc. producing changing reflected patterns when shaken.
Endoscope - Instrument used to examine the interior of a hollow organ or cavity of the body
Oscilloscope - Device for viewing oscillations by a display on the screen of a cathode-ray tube.
Periscope - Apparatus with a tube and mirrors, by which an observer in a trench, submerged submarine, or at the back of a crowd etc., can see things otherwise out of sight
Crescograph - Instrument for measuring growth in plants
Seismograph - Instrument that records the force, direction, etc., of earthquakes.
Cardiograph - Instrument recording heart movements.
Heliograph - Signalling apparatus reflecting sunlight in flashes.
Radiograph - Instrument recording the intensity of radiation.
The speed of light in vacuum is 186,000 miles per second or 300,000,000 m/s
The speed of light is slower in transparent mediums like water, glass and air and depends upon the refractive index of the medium.
Light is the visible part of electromagnetic spectrum and the frequency of light lies between 4 x 1014 Hz to 8 x 1014 Hz
Colour of light with smallest wavelength is Violet with a wavelength of about 400 nanometers.
Colour of light with longest wavelength is Red with a wavelength of about 650 nanometers.
The study of properties and behaviour of light is known as Optics.
Sunlight takes 8 minutes and 20 seconds to reach the Earth.
Light takes about 1.3 seconds to travel from the Earth to the Moon.
Three dimensional imaging using interference of light is known as Holography.
System of light excitation used in surgeries, printers etc. is LASER.
The colour of light which is most conducive to photosynthesis is Blue.
Refraction of light
Dispersion of light
Rainbows are formed
Interference of light
Beautiful colours are seen in soap bubbles and oil films on water
Scattering of light rays of small wavelengths
Sky appears blue
Sun appears red during sunrise and sunset
Facts about Sound
Facts to Remember
The speed of sound is
The audible range of sound in human beings is
20 Hz to 20,000
The level of sound prolonged exposure beyond which may cause permanent hearing loss
A woman’s voice is shriller than a man’s voice because of higher
The animals which produce sounds of high pitch and frequency to communicate and locate each other
Dolphins and elephants
The loudness of sound is measured in
Stringed instruments have boxes attached to increase the
Loudness of the sound produced
The minimum distance which is required to hear an echo
The system of sound reflection used to find the depth of oceans
SONAR (Sound navigation ranging)
The phenomenon which makes the sound of an approaching train shriller
Sounds cannot travel in vacuum.
Sounds travel faster in metals than in air.
Sonic boom occurs when a super sonic aircraft crosses the sound barrier.
Used in magnifying glass.
Used to correct the vision of long-sighted persons.
Used in spy holes on doors to check the visitors.
Used to correct the vision of short-sighted persons.
Uses of Concave Mirrors
Used by doctors to focus light inside the ears, mouth and throat.
Used as shaving mirrors to see an enlarged view of face.
Used as reflectors in torches and vehicle headlights to form powerful beams.
Used in driving mirror to give a view of the traffic behind.
Used at blind corners of roads/driveways to enable vehicles to see the traffic around the corner.
Used as looking glass.
Used in periscope used in ships, aircraft etc.
Used in kaleidoscope, a children's toy.
Position of object
Position of image
Nature of image
At focus (F)
Real, diminished, inverted
Beyond centre of curvature (C)
Between F and C
Real, diminished and inverted
Real, same size, inverted
Between C and F
Real, enlarged, inverted
Real, enlarged, inverted
Between F and P
Behind the mirror
Virtual, enlarged and upright
Images formed by Convex Mirror
Position of object
Position of image
Nature of image
Irrespective of the position
Behind the mirror
Virtual, diminished, upright
Electrical and Electronic Components
A resistor is a device which resists the flow of current in a circuit, thus reducing the voltage available to the load.
Usage : The conventional regulator of a fan is a resistor.
A capacitor is a storage device which may be used as a timer, phase splitter etc.
Usage : All domestic fans have capacitors to split the phase of AC, the starter of a flourescent tubelight is a capacitor.
An inductor is a device which resists changes in electric current passing through it. It consists of a conductor such as a wire, usually wound into a coil. Note that an inductor opposes change in current while a resistor just resists the flow of current.
Usage : The choke of a tube light is an inductor.
A transformer is a device that transfers electrical energy through electromagnetic induction. Transformers may be used to increase or decrease the alternating voltages in electric power applications.
Usage : A voltage stabiliser, a mobile charger etc contain a transformer.
A diode is device that restricts the flow of electric current in only one direction.
Usage : Diodes are commonly used in rectifiers which are used to convert A.C. (alternating current) to D.C. (direct current)
A transistor is a device usually made from semi-conductor material used to control the flow of current. Usage : Transistors are commonly used as amplifiers and have variety of uses in electronic equipment like radio, tv etc.