Organic Chemistry
Organic chemistry is that branch of chemistry which deals with the study of compounds of carbon with hydrogen (hydrocarbons), and their derivatives. Presently about five million organic compound are known. Organic compounds were found to contain mainly hydrogen and carbon. Therefore, organic chemistry is defined as the study of hydrocarbons and their derivatives. Most atoms are only capable of forming small molecules. However one or two can form larger molecules. By far and away the best atom for making large molecules with is Carbon. Carbon can make molecules that have tens, hundreds, thousands even millions of atoms! The huge number of possible combinations means that there are more Carbon compounds that those of all the other elements put together! A single Carbon atom is capable of combining with up to four other atoms. We say it has a valency of 4. Sometimes a Carbon atom will combine with few that will combine with itself. In other words Carbon combines with other Carbon atoms. This means that Carbon atoms can form chains and rings onto which other atoms can be attached. This leads to a huge number of different compounds. Organic Chemistry is essentially the chemistry of Carbon. Carbon compounds are classified according to how the Carbon atoms are arranged and what other groups of atoms are attached.
Hydrocarbons: The simplest Organic compounds are made up of only Carbon and Hydrogen atoms only. Even these run into thousands! Compounds of Carbon and Hydrogen only are called Hydrocarbons.
Alkanes: In the alkanes, all four of the Carbon valency bonds are taken up with links to different atoms. These types of bonds are called single bonds and are generally stable and resistant to attack by other chemicals. Alkanes contain the maximum number of Hydrogen atoms possible. They are said to be saturated. The simplest Hydrocarbon is:
Methane: \[C{{H}_{4}}\]this is the simplest member of a series of hydrocarbons. Each successive member of the series has one more Carbon atom than the preceding member.
Polythene is a very large alkane with millions of atoms in a single molecule. Apart from being flammable, alkanes are stable compounds found underground.
Alkenes: Another series of compounds is called the alkenes. These have a general formula: CnH2n. These compounds are named in a similar manner to the alkanes expect that the suffix is -end. Alkenes have fewer hydrogen atoms than the alkanes. The extra valencies left over occur as double bonds between a pair of Carbon atoms. The double bonds are more reactive than single bonds making the alkenes chemically more reactive. The simplest alkenes are listed in the table below:
Ethane (used as an industrial starter chemical): \[{{C}_{3}}{{H}_{4}}.\]
Propene: \[{{C}_{4}}{{H}_{6}}.\]
Butane: \[{{C}_{4}}{{H}_{8}}.\]
Pentene: \[{{C}_{5}}{{H}_{10}}.\]
Hexane: C6H12.
Alkynes: A third series are the alkynes. These have the following formula: \[Cn{{H}_{2}}n-2.\]These more...
An atom is the smallest particle of the element that can exist independently and retain all its chemical properties.
Dalton’s atomic theory, which suggested that the atom was indivisible and indestructible. But the discovery of two fundamental particles (electrons and protons) inside the atom, led to the failure of this aspect of Dalton’s atomic theory.
Thomson proposed that:
(i) An atom consists of a positively charged sphere and the electrons are embedded in it.
(ii) The negative and positive charges are equal in magnitude. So, the atom as a whole is electrically neutral.
Rutherford’s alpha-particle scattering experiment led to the discovery of the atomic nucleus. Rutherford’s model of the atom proposed that a very tiny nucleus is present inside the atom and electrons revolve around this nucleus. The stability of the atom could not be explained by this model.
Neil’s Bohr’s model of the atom was more successful. He proposed that electrons are distributed in different shells with discrete energy around the nucleus. If the atomic shells are complete, then the atom will be stable and less reactive.
Chadwick discovered presence of neutrons in the nucleus of an atom. So, the three sub-atom particles of an atom are: (i) electrons, (ii) protons and (iii) neutrons. Electrons are negatively charged, protons are positively charged and neutrons have no charges. The mass of an electron is about 1/2000 times the mass of a hydrogen atom. The mass of a proton and a neutron is taken as one unit each.
We know that protons are present in the nucleus of an atom. It is the number of protons of an atom, which determines its atomic number. It is denoted by ‘Z’. All atoms of an element have the same atomic number, Z. In fact, elements are defined by the number of protons they possess.
Mass of an atom is practically due to protons and neutrons alone. These are present in the neutrons of an atom. Hence protons and neutrons are also called nucleons. Therefore, the mass of an atom resides in its nucleus.
Isotopes are atoms of the same element, which have different mass numbers.
Isobars are atoms having the same mass number but different atomic numbers.
To bind a nucleus together there must be a strong attractive force of a totally different kind. It must be strong enough to overcome the repulsion between the (positively charged) protons and to bind both protons and neutrons into the tiny nuclear volume. This force is called Nuclear Force.
The nuclear force is much stronger than the Coulomb force acting between charges or the gravitational forces between masses. The nuclear force between neutron-neutron, proton-neutron more...
Temperature is a relative measure, or indication of hotness or coldness.
Heat is the form of energy transferred between two (or more) systems or a system and its surroundings by virtue of temperature difference. The SI unit of heat energy transferred is expressed in joule (J) while SI unit of temperature is kelvin (K), and ?C is a commonly used unit of temperature.
Thermometer is a device used for measuring temperatures. The two familiar temperature scale are the Fahrenheit temperature scale and the Celsius temperature scale. The Celsius temperature (tC) and the Farenheit temperature (tF) are related by:
In principle, there is no upper limit to temperature but there is a definite lower limit- the absolute zero. This limiting temperature is below zero on the celsius scale of temperature.
Clinical thermometer is used to measure our body temperature. The range of this thermometer is from to For other purpose, we use the laboratory thermometers. The range of these thermometer is usually from - to The normal temperature of the human body is
The heat flows from a body at a higher temperature to a body at a lower temperature. There are three ways in which heat can flow one object to another. These are conduction, convection and radiation.
The process by which heat is transferred from the hotter end to the colder end of an object is known as conduction. In solids generally, the heat is transferred by the process of conduction.
The material which allow heat to pass through them easily are conductors of heat. For examples, aluminum, iron and copper. The materials which easily are poor conductors of heat such as plastic and wood. Poor conductors are known as insulators.
In convention heat is carried from one place to another by the actual movement of liquid and gases. In liquids and gases the heat is transferred by convection
The people living in the coastal areas experience an interesting phenomenon. During the day, the land gets heated faster than the water. The air over the land becomes hotter and rises up. The cooler air from the sea rushes in towards the land to take its place. The warm air from the land moves towards the sea to complete the cycle. The air from the sea is called the sea breeze. At night it is exactly the reverse. The water cools down more slowly than the land. So, the cool air from the land moves towards the sea. This is called the land breeze.
The transfer of heat by radiation does not require any medium. It can take place whether a medium is present or not.
To understand light you have to know that what we call light is what is visible to us. Visible light is the light that humans can see. Other animals can see different types of light. Dogs can see only shades of gray and some insects can see light from the ultraviolet part of the spectrum.
As far as we know, all types of light move at one speed when in a vacuum. The speed of light in a vacuum is 299,792,458 meters per second.
Any medium through which light can travel is an optical medium. If this medium is such that light travels with equal speed in all directions, then the medium is called a homogeneous. The homogeneous media through which light can pass easily, are called transparent media. The media through which light cannot pass, are called opaque media. Again the media through which light can pass partly, are called translucent media.
LIGHT TRAVELS ALONG A STRAIGHT LINE.
Light is reflected from all surfaces. Regular is reflection takes place when light is incident on smooth, polished and regular surfaces.
After striking the surface, the ray of light is reflected in another direction. The light ray, which strikes any surface, is called the incident ray. The ray that comes back from the surface after reflection is known as the reflected ray.
The angle between the normal and incident ray is called the angle of incidence. The angle between the normal and the reflected rays is known as the angle of reflection.
Two laws of reflection are:
The angle of incidence is equal to the angle of reflection.
Incident ray, reflected ray and the normal drawn at the point of incidence to the reflecting surface, life in the same plane.
When all the parallel rays reflected from a plane surface are not parallel, the reflection is known as diffused or irregular reflection. On the other hand reflection from a smooth surface like that of a mirror is called regular reflection.
When rays of light coming from a point or source, after reflection or refraction, actually meet at another point or appear to diverge from another point, the second point is called the image of the first point. Images may be of two types, viz., (i) real and (ii) virtual.
An image which can be obtained on a screen is called a real image. An image which cannot be obtained on a screen is called a virtual image.
The image formed by a plane mirror is erect. It is virtual and is of the same size as the object. The image is at the same distance behind the mirror as more...
The word magnet is derived from the name of an island in Greece called Magnesia where magnetic ore deposits were found, as early as 600 BC. Magnetite, an iron ore, is a natural magnet. It is called lodestone.
When a bar magnet is freely suspended, it points in the north-south direction. The tip which points to the geographic north is called the north pole and the tip which points to the geographic south is called the south pole of the magnet. There is a repulsive force when north poles (or south poles) of two magnets are brought close together. Conversely, there is an attractive force between the north pole of one magnet and the south pole of the other.
The properties of a magnet are
it attracts small piece of Iron towards it.
it always ernes to rest in north-south direction when suspended freely.
like poles repel, unlike poles attracts each other
Magnetic poles always exist in pairs.
the strength of a magnet is maximum at poles located near the ponds.
The phenomenon due to which an unmagnetized magnetic substance behaves like a magnet, due to the presence of some other magnet, is called magnetic induction. Magnetic induction takes place first then magnetic attraction.
Magnetic induction depends upon the nature of magnetic substance. Magnetic induction is inversely proportional to the distance between inducing magnet and the magnetic substance. More powerful the inducing magnet, the more strong will be the magnetism in magnetic substance.
The space around the magnet where its influence can be detected is called the magnetic field.
A curve in a magnetic field, along with a free north magnetic pole will move, is called magnetic line force. The direction of magnetic lines of force is the direction in which free North Pole will move in a magnetic field.
They travel from north to South Pole outside the magnet and from south to North Pole inside the magnet.
They mutually repel each other
They never Intersect with each other
The earth behaves as a magnet with the magnetic field pointing approximately from the geographic south to the north. At a particular place on earth, the magnetic north is not usually in the direction of the geographic north. The angle between the two directions called declination.
B. Electricity
The phenomenon due to which a suitable combination of bodies on rubbing, get electrified is called electricity. If a charge on a body is not allowed to flow. It is called the static electricity.
Matters are made of atoms. An atom is basically composed of three different components - electrons, protons, and neutrons. An electron can be removed easily from an atom. When more...
Motion: In physics, motion is change of location or position of an object with respect to time. Mechanical motion is of two types, transitional (linear) and rotational (spin).
SPEED: The speed of a moving body is the rate at which it covers distance i.e. the distance it covers per unit of time.
Speed: (distance travelled/ time required.) The S.I. Unit of speed is ms.
VELOCITY: The distance covered by an object in a specified direction in unit time interval is called velocity. The S.I. Unit of velocity is m/s.
Average velocity can be calculated by dividing displacement over time.
The instantaneous velocity shows the velocity of an object at one point.
The difference between speed and velocity is: Speed is the distance travelled by an object in a particular time. Velocity is the speed in a particular direction.
ACCELERATION: When an object's velocity changes, it accelerates. Acceleration shows the change in velocity in a unit time. Velocity is measured in meters per second, m/s, so acceleration is measured in (m/s)/s, or m/s2, which can be both positive and negative. The symbol for acceleration is a (boldface).
When the velocity decreases the body is said to undergo retardation or deceleration.
Acceleration Due to Gravity: Galileo was the first to find out that all objects falling to Earth have a constant acceleration of 9.80 m/s2 regardless of their mass. Acceleration due to gravity is given a symbol g, which equals to 9.80 m/s2.
FORCE: Force can be defined as a push or a pull. (Technically, force is something that can accelerate objects.). Force is measured by N (Newton). A force that causes an object with a mass of 1 kg to accelerate at 1 m/s is equivalent to 1 Newton.
Newton’s law of universal gravitation states that every massive particle in the universe attracts every other massive particle with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
In equation form, the gravitational force where r is the distance between two bodies of masses rn1 and m2 and 6 the universal gravitational constant.
Centripetal Force: For a body to move in a circle there must be a force on it directed towards the centre. This is called the centripetal force and is necessary to produce continuous change of direction in a circular motion.
The magnitude of the centripetal force on an object of mass m moving at a speed v along a path with radius of curvature r more...
Sound is a form of energy and like all other energies, sound is not visible to us. It produces a sensation of hearing when it reaches our ears. Sound cannot travel through vacuum.
Sound is produced due to vibration of different objects. The matter or substance through which sound is transmitted is called a medium. It can be solid, liquid or gas. Sound moves through a medium from the point of generation to the listener.
In longitudinal wave the individual particles of the medium move in a direction parallel to the direction of propagation of the disturbance. The particles do not move from one place to another but they simply oscillate back and forth about their position of rest. This is exactly how a sound wave propagates, hence sound waves are longitudinal waves. Sound travels as successive compressions and rarefactions m the medium. In sound propagation, it is the energy of the sound that travels and not the particles of the medium.
There is also another type of wave, called a transverse wave. In a transverse wave particles do not oscillate along the line of wave propagation but oscillate up and down about their mean position as the wave travels. Thus a transverse wave is the one in which the individual particles of the medium move about their mean positions in a direction perpendicular to the direction of wave propagation. Light is a transverse wave but for light, the oscillations are not of the medium particles or their pressure or density − it is not a mechanical wave.
To and fro motion of an object is known as vibration. This motion is also called oscillatory motion.
Amplitude and frequency are two important properties of any sound.
The loudness or softness of a sound is determined basically by its amplitude. The amplitude of the sound wave depends upon the force with which an object is made to vibrate.
The change in density from one maximum value to the minimum value and again to the maximum value makes one complete oscillation.
The distance between two consecutive compressions or two consecutive rarefaction is called the wavelength
The time taken by the wave for one complete oscillation of the density or pressure of the medium is called the time period, T.
The number of complete oscillations per unit time is called the frequency. The frequency is expressed in hertz (Hz).
Larger the amplitude of vibration, louder is the sound. Higher the frequency of vibration, the higher is the pitch, and shriller is the sound.
The frequency determines the shrillness or pitch of a sound. If the frequency of vibration is higher, we more...
Units and Measurement
(i). Physics is a quantitative science, based on measurement of physical quantities. Certain physical quantities have been chosen as fundamental or base quantities (such as length, mass, time, electric current, thermodynamic temperature, amount of substance, and luminous intensity).
(ii). Each base quantity is defined in terms of a certain basic, arbitrarily chosen but properly standardized reference standard called unit (such as meter, kilogram, second, ampere, kelvin, mole and candela). The units for the fundamental or base quantities are called fundamental or base units.
(iii). Other physical quantities, derived from the base quantities, can be expressed as a combination of the base units and are called derived units. A complete set of units, both fundamental and derived, is called a system of units.
(iv). The International System of Units (SI) based on seven base units is at present internationally accepted unit system and is widely used throughout the world. The SI units are used in all physical measurements, for both the base quantities and the derived quantities obtained from them. Certain derived units are expressed by means of SI units with special names (such as joule, newton, watt, etc).
(v). The SI units have well defined and internationally accepted unit symbols (such as m for meter, kg for kilogram, s for second, A for ampere, N for newton etc.). Physical measurements are usually expressed for small and large quantities in scientific notation, with powers of 10. Scientific notation and the prefixes are used to simplify measurement notation and numerical computation, giving indication to the precision of the numbers.
(vi). Unit of Length: The SI Unit of length is meter (m). Various other metric units used for measuring length are related to the meter by either multiples or submultiples of 10.Thus,
1 kilometer = 1000 ( or 103) m
1 centimeter = 1/100 ( or 0-2) m
1 millimeter = 1/1000 ( or 10-3) m
Very small distance are measured in micrometer or microns (urn), angstroms (A), nanometer (nm) and femtometre (fm).
1m = 106 µm
1m = 109 nm
1m =1010 Å
1m=1015 fm
For really large distances, the light year is the unit of choice. A light year is the distance light would travel m a vacuum after one year. It is equal to some nine quadrillion meters (six trillion miles). 1 light year .
Unit of Mass: The SI Unit of mass is kilogram (kg). Various other metric units used for measuring mass are related to the kilogram by either multiples submultiples of 10. Thus,
1 tonne(t) = 1000 ( or 103) kg
1 gram(g) = 1/1000 ( or 0-32) kg
1 milligram(mg) = 10-6Kg
Unit of Time: The SI unit of time is the second (s).
Mechanical waves require a material medium to travel (air, water, ropes). These waves are divided into three different types.
Transverse waves cause the medium to move perpendicular to the direction of the wave.
Longitudinal waves cause the medium to move parallel to the direction of the wave.
Surface waves are both transverse waves and longitudinal waves mixed in one medium.
Electromagnetic waves do not require a medium to travel (light, radio).
Matter waves are produced by electrons and particles.
A point of maximum positive displacement in a wave, is called crest, and a point of maximum negative displacement is called trough.
Measuring Waves: Any point on a transverse wave moves up and down in a repeating pattern. The shortest time that a point takes to return to the initial position (one vibration) is called period, T.
The number of vibrations per second is called frequency and is measured in hertz (Hz). Herat’s the equation for frequency: f = 1 / T
The shortest distance between peaks, the highest points, and troughs, the lowest points, is the wavelength,
By knowing the frequency of a wave and its wavelength, we can find its speed. Here is the equation for the velocity of a wave:
However, the velocity of a wave is only affected by the properties of the medium. It is not possible to increase the speed of a wave by increasing its wavelength. By doing this, the number of vibrations per second decreases and therefore the velocity remains the same.
The amplitude of a wave is the distance from a crest to where the wave is at equilibrium. The amplitude is used to measure the energy transferred by the wave. The bigger the distance, the greater the energy transferred.
When a force acting on a body produces a change in the position of the body, work is said to be done by the force. Work done on an object is defined as the magnitude of the force multiplied by the distance moved by the object in the direction of the applied force. The unit of work is joule: 1 joule = 1 newton 1 meter. Work done on an object by a force would be zero if the displacement of the object is zero.
Power is defined as the rate of doing work. Power = (work done) / (time taken). The SI unit of power is watt. 1 W = 1 Joule/second. The unit of power is also horse power. It is the power of an agent which can work at the rate of 550 foot pounds per second or 33,000 foot pounds per minute.
An object having capability to do work is said to possess energy. Energy has the same unit as that of work.
An object in motion possesses what is known as the kinetic energy of the object. An object of mass, m moving with velocity v has a kinetic energy of
The energy possessed by a body due to its change in position or shape is called the potential energy. The gravitational potential energy of an object of mass, m raised through a height, h from the earth’s surface is given by mgh.
According to the law of conservation of energy, energy can only be transformed from one form to another; it can neither be created nor destroyed. The total energy before and after the transformation always remains constant.
Energy exists in nature in several forms such as kinetic energy, potential energy, heat energy, chemical energy etc. The sum of the kinetic and potential energies of an object is called its mechanical energy.
Pressure: Pressure is defined as force acting per unit area. Pressure = force/area. The SI unit of pressure is newton per meter squared or Pascal.
The same force acting on a smaller area exerts a larger pressure, and a smaller pressure on a larger area. This is the reason why a nail has a pointed tip, knives have sharp edges and buildings have wide foundations.
All liquids and gases are fluids. A solid exerts pressure on a surface due to its weight. Similarly, fluids have weight, and they also exert pressure on the base and walls of the container in which they are enclosed, Pressure exerted in any confined mass of fluid is transmitted undiminished in all directions.
All objects experience a force of buoyancy when they more...
