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Basic Physical Science

Gases - Facts to Remember


Fact to remember

Name of the gas

Gas most abundant in earth's atmosphere

Nitrogen (78%)

Percentage of oxygen in earth's atmosphere

21% (appx)

The lightest gas


The heaviest gas


Tear Gas

Ammonia​​ (NH3)

Marsh gas


Laughing gas

Nitrous​​ Oxide​​ (N2O)

Natural gas

Mainly methane with small quantities of ethane and propane

Gobar gas

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

Carbon monoxide

The gas which is responsible for the formation of brown air in traffic congested cities


Nitrogen Dioxide

Major gaseous pollutant of areas located near thermal power station

Suphur dioxide

Strong smelling substance added to LPG

Ethyl Mercaptan or Ethanethiol

Gases responsible for depletion of ozone layer

Chloroflouro carbons

Gas responsible for acid rain

Sulphur dioxide

Gas used in gas welding and also artificial ripening of fruits


Gas used in electric bulbs


Gas used in flourescent lamps

Mercury vapour

Gas used in LPG

Butane, Propane and Ethane

Gas used in refrigeration

Freon (Diflouro Dichloro Methane)

Gas used as an anaesthetic in dental surgery

Nitrous OxideA


About Metals

  • 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.

Metals, Alloys and Ores

Important Alloys



Combination of


Aluminium and Copper


Copper and Zinc


Copper and Tin


Iron and Nickel

Stainless steel

Iron, Chromium and Nickel

German Silver

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












Bornite, Chalcocite
















Wolframite, Scheelite








Metal Processes

    • Annealing

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.


    • Hardening

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.


    • Tempering

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.


    • Galvanisation

It is a process in which a protective zinc coating is applied on iron to prevent it from rusting.


    • Welding

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.


    • Brazing

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.


    • Soldering

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.


    • Electroplating

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.


    • Smelting

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.

Important Scientific Laws

Avogadro's Law (Gases)

  • 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)

Boyle's Law (Gases)

  • 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

Charles' Law (Gases)

  • 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.

Coulomb's Law (Electrostatics)

  • 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.

Faraday's Law of Electromagnetic Induction

  • 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.

Hooke's Law of Elasticity

  • 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.

Joule's Law (Electricity)

  • 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.

SI Units of Measurement

Base Units


Physical Quantity

Unit of Measurement







Electric Current




Thermodynamic Temperature


Amount of Substance


Luminous Intensity



Derived Units


Physical Quantity

Unit of Measurement



















Electric Charge


Potential Difference


Electromotive Force


Electric Resistance


Electric Capacitance


Electric Conductance




Magnetic Flux


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.

Facts about Light

  • 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.

Phenomenon of Light - Visible Effects



Visible Effect





Refraction of light

  • Day is​​ lengthened

  • Stars appear to​​ twinkle

  • Mirages are​​ formed

  • Sun or moon​​ appears​​ larger in size when at horizon

  • Stick immersed in water appears bent at the​​ point​​ of separation

  • A person standing​​ inside​​ water appears​​ shorter

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

343 m/s

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


85 dB

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

17 metres

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

Doppler effect

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.


Uses of Convex Lens

  • Used in magnifying​​ glass.

  • Used to correct the vision of long-sighted​​ persons.

Uses of Concave Lens

  • 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.

Uses of Convex Mirrors

  • 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.

Uses of Plane Mirrors

  • Used as looking​​ glass.

  • Used in periscope used in ships, aircraft​​ etc.

  • Used​​ in kaleidoscope, a children's​​ toy.

Images formed by Concave Mirror


Position of object

Position of image

Nature of image

At infinity

At focus (F)

Real, diminished, inverted

Beyond centre of curvature (C)

Between F and C

Real, diminished and inverted

At C

At C

Real, same size, inverted

Between C and F

Beyond C

Real, enlarged, inverted

At F

At infinity

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

  • Resistor

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.

  • Capacitor

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.

  • Inductance

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.

  • Transformer

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.

  • Diode

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)

  • Transistor

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.