Neutrons, and• Electron.The nucleus of an atom is made up of protons and neutrons. The electron of an atom resolves round the nucleus of an atom in an orbit known as shells.Neutrons are neutral and have no electrical charge while protons and electrons are electrically charged. While Protons are positively charged and have a relative charge of +1, electrons are negatively charged with a relative charge of -1. STRUCTURE OF THE ATOM Matter is anything that has mass and occupies space. Atoms are fundamental building blocks of matter that cannot be further divided by any chemical means. What are elements?Elements are constituents of matter. There are 92 natural elements. Elements like hydrogen, carbon, nitrogen and oxygen are elements that make up the majority of living things. Other groups of element that exist in living things are: magnesium, calcium, phosphorus, sodium, potassium.Many elements were discovered before the late 1800’s. A Russian scientist Dmitri Mendeleev then proposed an arrangement of elements based on their atomic masses. In the modern time, elements are no longer arranged based on their atomic masses but according to their atomic numbers.The word atom is a derivative of the Greek word atom which means undividable. The Greeks came to a conclusion that matter could be further divided into particles that are too tiny to be seen with the naked eye. These tiny indivisible particles of matter were referred to as atoms.An atom is made up of three types of particles:• Protons• Neutrons, and• Electron.The nucleus of an atom is made up of protons and neutrons. The electron of an atom resolves round the nucleus of an atom in an orbit known as shells.Neutrons are neutral and have no electrical charge while protons and electrons are electrically charged. While Protons are positively charged and have a relative charge of +1, electrons are negatively charged with a relative charge of -1.The number of protons in the nucleus of an atom is known as its atomic number. Atoms are arranged in atomic number order in the periodic table while electrons are arranged in energy levels or shells. Each energy level holds a definite numbers of electrons.The electronic structure of an atom is an explanation of the manner the electrons are arranged, which can be demonstrated in a diagram or through numbers. The position of an element in the periodic table and its electronic structure interrelated.The atomic mass of an element is greatly determined by the number of protons and neutrons in its nucleus. For instance, in a mass number of 150; 149 lbs which equivalent to 15 oz is protons and neutrons while only 1 oz. is the electron’s mass. The mass of an electron is extremely small - 9.108 X 10-28 grams.It is the number of protons in an atom that establishes the atomic number. For example, Hydrogen is with an atomic number of 1.The number of protons in an element is invariable (example, the number of proton in Hydrogen (H) =1 and that of Uranium (Ur) = 92 but the number of neutron may well differ, therefore the mass number (protons + neutrons) of an element could differ.A particular element may have differing numbers of neutrons; the different forms of an element with the same number of proton but with differing numbers of neutron are referred to as isotopes. Isotopes have the same chemical properties but the physical properties of a number of isotopes might be different.Some isotopes are radioactive in nature. This means that give out energy while they decompose and break down to a more stable form. This gives rise to another element.Half-life of a radioactive element is the time that it takes for half of the atoms of that element to decay into stable form. An example of element that exhibits isotopy is oxygen. The element-Oxygen with an atomic number of 8 may possibly have 8 or 9, or 10 neutrons. Atomic Symbols and Isotopes The atom of every element is composed of electrons, protons and neutrons. Atoms of the same element possess the same number of protons and electrons but the number of neutrons can vary. When the neutrons vary such elements are referred to as isotopes. Due to these isotopes, it got crucial to formulate a notation to differentiate an isotope from the other. This notation is known as the atomic symbol. The atomic symbol is usually denoted with three different letters:1. The X: This is used to represent the element.2. The A: This is a symbol that represents the atomic number. This is the number of protons situated on the left side of letter A as a subscript.3. The Z: This is used to denote the mass no. The mass number is equal to the number of protons and neutrons in the isotope usually placed on top of letter Z as a left superscript.Relative atomic mass (Ar) of an element is the ratio of the average mass of atoms of that element to 1/12 of the mass of carbon-12 isotope. IUPAC’s definition of Relative atomic mass: An atomic weight or relative atomic mass of an element is the ratio of the standard mass per atom of the element to 1/12 of the mass of an atom of 12C. Relative atomic mass scale The mass of atoms and other tiny particles is calculated on the atomic mass scale as a relative number put side by side the carbon atom. The carbon 12 atom is allocated with the value of exactly 12.0000 on the scale and the whole thing else is calculated with respect to that figure.Carbon atomMagnesium atomHydrogen atommass = 12mass = 2 x carbon atommass = 1/12 x carbon atomThe magnesium atom has double the atomic mass of the carbon atom, so a magnesium atom has a relative mass of 24.3 helium atoms have atomic mass equivalent to the mass of a carbon atom. This means that each of the 3 helium atoms has a relative atomic mass of 4. The relative atomic mass of an element can either be written as Ar or RAM for short.Relative molecular massMolecules are merely groups of atoms. Therefore they are as well measured on the relative mass scale with carbon 12 just like in relative atomic mass.Hydrogen atomOxygen atomwater moleculemass = 1mass = 16mass = (2 x 1) + 16 = 18A water molecule for example has a mass of 3/2 times relative that of a carbon 12 atoms, consequently the relative molecular mass of water is equal to 18.The relative molecular mass of a substance is obtained by adding up the relative masses of all the atoms that make up a molecule of that substance.All masses are calculated relative to the mass of a 12C isotope = 12.0000 atomic mass units.Since relative molecular mass is a comparative calculation, it is not denoted with any unit.For instance: Benzene has the molecular formula C6H6A benzene molecule contains 6 carbon atoms and 6 hydrogen atoms.The relative molecular mass = (6 x relative atomic mass of carbon) + (6 x relative atomic mass of hydrogen)The relative molecular mass of benzene = (6 x 12) + (6 x 1) = 78The relative molecular mass of an element can either be written as RMM or Mr for short. Mole: The mole is the amount of substance that contains as many elemental particles - atoms, molecules, ions, electrons as the number of atoms in 12g of carbon-12 isotope.1 mole of a substance is equal to 6.022 x 1023 itemsSubatomic Particles of an atom and their propertiesAll atoms are composed of three subatomic particles: Protons, neutron and electrons.The properties of these three sub atomic particles are tabulated below:Particle Charge Mass (g) Mass (amu)Proton+11.6727 x 10-24g1.007316Neutron01.6750 x 10-24g1.008701Electron-19.110 x 10-28 g0.000549What we have used in the above table is a unit of mass called the atomic mass unit (amu). This is a better unit to use than grams when discussing masses of atoms. It is defined with the intention that both protons and neutrons have a mass of just about 1 amu. The significant points to remember are bulleted below:• Protons and neutrons have roughly the same mass, while the electron is more or less 2000 times less heavy.• Protons and electrons bear charges of equivalent size, but opposite charge. Neutrons have no charge ie they are neutral.It was at one time believed that protons, neutrons and electrons were spread out in a somewhat uniform fashion to form the atom according to J.J. Thompson’s plum pudding model of the atom but in reality the actual arrangement of the atom is rather different.Electrons move about rapidly just about the nucleus and make up almost the whole volume of the atom. The quantum mechanics are essential to give details of the motion of an electron about the nucleus, but we can say that the sharing of electrons round an atom is in a spherical form. The force that holds an atom together The electron which is negatively charged is attracted to the nucleus which is positively charged by a Columbic attraction.The protons and neutrons are mutually bonded in the nucleus by the strong nuclear force.The relationship between the structures of an atom with its propertiesChemical reactions occur when there is either a transfer or a sharing of electrons between atoms of same or different elements. What this means is that the chemical properties of an element is for the most part reliant on the number of electrons in one atom of that element. Protons as well play a noteworthy role for the reason that the propensity of an atom to either lose, gain or share electron is reliant on the electrical charge of the nucleus.Therefore, it is right to conclude that the chemical properties of an atom is reliant on the number of electrons and protons of the atom and the number of neutrons does not add to the chemical properties of that atom.On the other hand, the mass and radioactive properties of an atom are reliant on the number of protons and neutrons in the nucleus.Atomic Number (Z) -The no of protonsMass Number (A) - The no of protons] + [the no of neutrons]The number of protons, neutrons and electrons in an atom are uniquely specified by the following symbolASyC, where:• Sy = The symbol of an element like C, N, Cr) -defines the no of protons• A = The mass number-[the no of protons] + [the no of neutrons]• C = The net charge- [the no of protons] – [ the no of electrons]For instance: A neutral boron 10 atom with 10BA boron atom according to the periodic table has 5 protons in the nucleus Z = 5.Since the boron atom is a neutral atom, the number of electrons ought to be equal to the number of protons, 5 electrons.The mass number of Boron is 10. Therefore, the number of neutrons is A - Z = 10 - 5 = 5 neutrons. Polyatomic Ions IonIonic FormulaAmmuoniumNH4+CarbonateCO32+HydroxideOH-NitrateNO3-PhosphatePO43-SulfateSO42- Kinematics The concept of Kinematics is the study of motion without the force causing them and the mass of the body. Suppose a body of mass 2kg is pulled a distance of 10m by a force of 5N; kinematics studies only the movement in a giving direction without concern on the 5N force or the 2kg mass of the body.The motion of a body can either be in any of these forms:1. Random: Example is gaseous particles,2. Translational: Example is a moving car,3. Rotational: Example is a ceiling fan,4. Oscillatory: Example is swinging pendulum. Straight Line Motion (SLM) This is the motion of a body in a straight line. There are four parameters involved in the study of this motion of a body in a straight line. They are Displacement or Distance, Velocity, Acceleration and Time. Displacement This is the distance travelled in a specified direction. It is the shortest distance between two points. In kinematics it is represented with (s) and is mathematically related to velocity thus:s = vtWhere: s = displacementv = velocityt = timeThe unit of displacement is metre (m).Example 1A car with a uniform velocity of 10 m/s left Enugu at 10:00 am and arrived Nsukka at 10:30 am. Calculate its displacement.Solution:First let’s write down the terms given to us. We have:v = 10 m/sT = (10:30 – 10:00) = 30 minutes, Note: we need to further change this time to be in seconds. So 30 minutes would be:(30 x 60) sec = 1800 s.So from the formula, we have thats = vts = 10 x 1800s = 18000 m. Displacement and Distance Most often students who are new to physics find it very difficult to understand the difference between displacement and distance. We will quickly highlight the differences before we continue with the next section.Although these two quantities appear to be similar but displacement is a vector quantity and by so it is direction- aware while distance is a scalar quantity.To fully understand the terms scalar and vector in physics, we will go ahead and define the meaning of these terms.Scalars are quantities that have only magnitudeVectors are quantities that have both magnitude and directionA simple illustration of distance and displacement example is; if a man travels in a rectangular path from a starting point along the path and ends on the same spot he started, the displacement in this situation is zero while the distance is the length of the rectangular path from the starting point to the end point.It is also important to note that when an object changes direction and start moving in opposite direction it will effectively cancel its initial displacement.Distance can be measured by one of the following measuring tools and its unit of measurement is in meters.Use of stringMetre ruleVernier callipersMicrometre screw gauge Velocity Velocity is speed measured in a specified direction. Many misunderstand Speed to be Velocity. In Physics, the two mean different things. Speed is the rate of change of distance with time. Velocity is a vector quantity (i.e. it has both magnitude and direction) while speed is a scalar quantity (it has magnitude but no direction) - we shall treat it in the next tutorial.The unit of velocity is metre per second (m/s). Mathematically:Velocity (v) = s/tWhere s = displacement, t = time.Uniform velocity: A body is said to be in a uniform velocity when the ration (s/t) is constant - unchanging.Average Velocity (aV): Average velocity is the total distance travelled (Stotal ) divided by the total time taken (Ttotal).aV = Stotal /Ttotal Example 1 Calculate the velocity of a car that covered a distance of 250 metres in 25 seconds. Solution: We write down the given terms as always:S = 250mT = 25sv = s/tv = 250/25v = 10 m/s. Acceleration Acceleration is the rate of change of velocity with time. The unit of acceleration is metre per second squared (m/s2). Acceleration like velocity is a vector quantity that is why it is wrong to think that acceleration means the rate of change of speed with time. Mathematically Acceleration (a) is:a = v/tWhere v = velocity, t = time.Uniform acceleration: If the rate of change of velocity is constant, the acceleration is said to be uniform. This implies that:a = v/t = constant.If the velocity of a body is increasing with time, it is said to be accelerating, but if the velocity of a body is decreasing with time, it is said to be retarding or decelerating or experiencing retardation or deceleration. And then in such a case, it is important we notice the acceleration is said to be negative. Example I A body rolled from point X to point Y in 2 seconds with a velocity of 5m/s. Calculate the acceleration of the car. Solution: First, we note down our terms,t = 2 sv = 5 m/sFrom the formula a = v/ta = 5/2a = 2.5 m/s2 The Equation of Motion Deriving the equations of motion, it was noticed that if a body starts with initial velocity ‘u’ accelerates uniformly along a straight line with acceleration ‘a’ and covers a distance ‘s’ in a time ‘t’ when its velocity reaches a final value ‘v’, then the distance ‘s’ covered is given by s = average velocity times time.s = u – v x t ……… (Equation 1)Also by definition, acceleration ‘a’ = rate of change of velocity and since ‘a’ is constant we will havea = (v-u)/t = v = u + at …………… (Equation II)Eliminating t from (Equation I) and (Equation II), we finedv2 = u2 + 2as ……… (Equation III)Eliminating ‘v’ from (Equation I) and (Equation II), we finds = ut + 1/2 at2 ……… ( Equation IV)Note:These four equations of motion are used in solving problems associated with uniformly accelerated motion. When using them, the following points should be noted.I. Ensure that all the units match. i.e., velocity in m/s, distance in m, acceleration in m/s2 and time in s.II. Each of the equations contains four of the five variables u, v, s, a, t. The values of three are normally given and the values of one or both unknowns are required to be found.III. To determine which equation to use in solving a particular problem,(a) Note down the given variables,(b) Note down the required variable,(c) Note down the un-given variable(d) Then the equation to use is the one that does NOT contain the un-given variable.Hint:Equation I does not contain aEquation II does not contain sEquation III does not contain tEquation IV does not contain vIV. Note the conversion formulae: 1km/h = 1000/ (60 x 60) m/s OR 36km/h = 10m/s OR 1m/s = 3.6km/h.V. Do not confuse s for distance with s the unit of time. Example I A car moves from rest with an acceleration of 0.2m/s2. Find its velocity when it has moved a distance of 50m. Solution: We note down the given variables, which are:a = 0.2m/s2s = 50mThe required variable is ‘v’ andThe un-given variable is t and the equation that doesn’t contain t is Equation III. So we use Equation III.v2 = u2 + 2asWe should also bear in mind that the initial velocity u of a moving body which started at rest is zero.So with that now, our u here will be 0m/s.v2 = 02 + 2 x 0.2 x 50v = √ (0 + 2 x 0.2 x 50)v = √ 20v = 4.47m/s. Example II A car is uniformly retarded and brought to rest from a velocity of 36km/h in 5sec. Find:(a) Its retardation(b) The distance covered during this period. Solution: Like before, write down the variables. Then we havev = 36km/ht = 5ss = ?(a) First, we should notice that by retardation, we are required to find the acceleration. Then the formula for acceleration isa = v/tand here we have v = 36km/h, we will need to change it to m/s before we proceed. So 36km/h = (36 x 1000) / (60 x 60) = 36000/3600 = 10m/sTherefore we now havea = 10/5a= 2m/s2(b) Now we have the acceleration, we need to find the distance covered, so we use (Equation IV). And I need someone to tell us why we should use Equation IV.So from equation IVs = ut + 1/2at2Note: initial velocity (u) in this case is zero, thenThen s = 0 + 1/2 x 2 x 25s = 25 m.Now let’s have one or two problem set for you to solve. Please try your hand on these questions. It will help you to fully understand this topic. Once you are done with it you can jump over to the next tutorial. Question I A train slows from 108km/h with a uniform retardation of 5m/s2. How long will it take to reach 18km/h? Question II What is the distance covered in question 1?You should try and solve the problem. Practising is a good way of learning. Some Physics Laws Amperes Law Amperes Law states that, for constant current flow, the flux of electrical current through a surface is proportional to the line integral of the magnetic field (counterclockwise) around its boundary Archimedes principle Archimedes principle indicates that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces. Archimedes principle is a law of physics fundamental to fluid mechanics Avogadros Hypothesis Avogadros hypothesis states that at the same temperature and pressure, the same volume of any gas will contain the same number of molecules. Boyles lawBoyles law Boyles law states that at a constant temperature the volume of a confined ideal gas varies inversely with its pressure. Brownian motion Brownian motion is the random motion of particles suspended in a fluid (a liquid or a gas) resulting from their collision with the quick atoms or molecules in the gas or liquid. Charless law Charless law states If the pressure of a gas remains constant, the volume of the gas will increase as the temperature increases. Compton effect Compton effect is a phenomenon in which a collision between a photon and a particle results in an increase in the kinetic energy of the particle and a corresponding increase in the wavelength of the photon Conservation of energy The law of conservation of energy stated that energy cannot be created or destroy but it can be transformed from one form to another. This implies that when energy is converted from one form to another, no energy is lost or created during the conversion process. Coulombs Law The interaction between charged objects is a non-contact force that acts over some distance of separation. Curies law In a paramagnetic material the magnetization of the material is (approximately) directly proportional to an applied magnetic field. However, if the material is heated, this proportionality is reduced: for a fixed value of the field, the magnetization is (approximately) inversely proportional to temperature Daltons law of partial pressures Daltons law (also called Daltons law of partial pressures) states that the total pressure exerted by the mixture of non-reactive gases is equal to the sum of the partial pressures of individual gases. Faradays Law Any change in the magnetic environment of a coil of wire will cause a voltage (emf) to be induced in the coil. No matter how the change is produced, the voltage will be generated. The change could be produced by changing the magnetic field strength, moving a magnet toward or away from the coil, moving the coil into or out of the magnetic field, rotating the coil relative to the magnet, etc. Faradays First Law Of Electrolysis The mass of the substance librated or deposited on an electrode during electrolysis is directly proportional to the quantity of electric charge passed through the electrolyte. Faradays Second Law Of Electrolysis If the same quantity of electricity (electric charge) is passed through different electrolytes, the mass of an substance librated or deposited altered at an electrode is directly proportional to their chemical equivalents. Gausss law of Electricity The net number of electric field lines passing through a Gaussian surface is proportional to the total charge enclosed by the Gaussian surface. Gausss Law of Magnetism The net number of magnetic field lines passing through a Gaussian surface is always zero. Hookes law Hookes law is a principle of physics that states that the force F needed to extend or compress a spring by some distance X is proportional to that distance. Ideal Gas Law An ideal gas is defined as one in which all collisions between atoms or molecules are perfectly eleastic and in which there are no intermolecular attractive forces. Joules first law Joules first law (Joule heating), a physical law expressing the relationship between the heat generated and current flowing through a conductor. Joules second law Joules second law states that the internal energy of an ideal gas is independent of its volume and pressure, depending only on its temperature. Lenzs law Lenzs law is a common way of understanding how electromagnetic circuits obey Newtons third law and the conservation of energy. Newtons first laws of motion The first law states that a body remains at rest or in uniform motion in a straight line unless acted upon by a force. Newtons second laws of motion The second law states that a bodys rate of change of momentum is proportional to the force causing it. Newtons third laws of motion The third law states that when a force acts on a body due to another body, then an equal and opposite force acts simultaneously on that body Ohms law Ohms law emphasis the principle that the electric current passing through a conductor is directly proportional to the potential difference across it, provided that the temperature remains constant. The constant of proportionality is the resistance of the conductor Pascal’s principle Pascal’s principle states that in a fluid at rest in a closed container, a pressure change in one part is transmitted without loss to every portion of the fluid and to the walls of the container. Laws of reflection The incident ray, the reflected ray and the normal to the reflection surface at the point of the incidence lie in the same plane. The angle which the incident ray makes with the normal is equal to the angle which the reflected ray makes to the same normal. The reflected ray and the incident ray are on the opposite sides of the normal.(wikipedia) Law of Refraction Law of Refraction stated that When light travels from one medium to another, it generally bends. Snells Law Snells Law relates the indices of refraction n of the two media to the directions of propagation in terms of the angles to the normal. Uncertainty principle Uncertainty principle is any of a variety of mathematical inequalities asserting a fundamental limit to the precision with which certain pairs of physical properties of a particle known as complementary variables, such as position x and momentum p, can be known simultaneously (wikipedia) Van der Waals force Van der Waals force stated that the sum of the attractive or repulsive forces between molecules (or between parts of the same molecule) other than those due to covalent bonds, the hydrogen bonds, or the electrostatic interaction of ions with one another or with neutral molecules or charged molecules First law of thermodynamics The first law establishes a notion of internal energy for a thermodynamic system. Heat and work are forms of energy transfer. The internal energy of a thermodynamic system may change as heat or matter is transferred into or out of the system or work is done on or by the system Second law of thermodynamics An isolated physical system, if not already in its own internal state of thermodynamic equilibrium, spontaneously evolves towards it. In an isolated physical system, there is a tendency towards spatial homogeneity. Third law of thermodynamics There are various ways of expressing the third law. They derive from the statistical mechanical explanation of thermodynamics. They refer to ideally perfect theoretical models of physical systems. Optics Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light. Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties.Most optical phenomena can be accounted for using the classical electromagnetic description of light. Complete electromagnetic descriptions of light are, however, often difficult to apply in practice. Practical optics is usually done using simplified models.The most common of these, geometric optics, treats light as a collection of rays that travel in straight lines and bend when they pass through or reflect from surfaces. Physical optics is a more comprehensive model of light, which includes wave effects such as diffraction and interference that cannot be accounted for in geometric optics.Historically, the ray-based model of light was developed first, followed by the wave model of light. Progress in electromagnetic theory in the 19th century led to the discovery that light waves were in fact electromagnetic radiation.Some phenomena depend on the fact that light has both wave-like and particle-like properties. Explanation of these effects requires quantum mechanics. When considering lights particle-like properties, the light is modeled as a collection of particles called photons. Quantum optics deals with the application of quantum mechanics to optical systems.Optical science is relevant to and studied in many related disciplines including astronomy, various engineering fields, photography, and medicine (particularly ophthalmology and optometry). Practical applications of optics are found in a variety of technologies and everyday objects, including mirrors, lenses, telescopes, microscopes, lasers, and fiber optics. Classical optics Classical optics is divided into two main branches which are geometrical optics and physical optics. In geometrical, or ray optics, light is considered to travel in straight lines, while in physical or wave optics, light is considered to be an electromagnetic wave.Geometrical optics can be viewed as an approximation of physical optics which can be applied when the wavelength of the light used is much smaller than the size of the optical elements or system being modelled. Geometrical optics Geometrical optics, or ray optics, describes the propagation of light in terms of rays which travel in straight lines, and whose paths are governed by the laws of reflection and refraction at interfaces between different media.These laws were discovered empirically as far back as 984 AD and have been used in the design of optical components and instruments from then until the present day. They can be summarized as follows:• When a ray of light hits the boundary between two transparent materials, it is divided into a reflected and a refracted ray.• The law of reflection says that the reflected ray lies in the plane of incidence, and the angle of reflection equals the angle of incidence.• The law of refraction says that the refracted ray lies in the plane of incidence, and the sine of the angle of refraction divided by the sine of the angle of incidence is a constant. Physical optics In physical optics, light is considered to propagate as a wave. This model predicts phenomena such as interference and diffraction, which are not explained by geometric optics. The speed of light waves in air is approximately 3.0×108 m/s (exactly 299,792,458 m/s in vacuum).The wavelength of visible light waves varies between 400 and 700 nm, but the term light is also often applied to infrared (0.7–300 μm) and ultraviolet radiation (10–400 nm).The wave model can be used to make predictions about how an optical system will behave without requiring an explanation of what is waving in what medium. Light waves are now generally treated as electromagnetic waves except when quantum mechanical effects have to be considered. Wave and Sound Sound is a mechanical wave that results from the back and forth vibration of the particles of the medium through which the sound wave is moving. If a sound wave is moving from left to right through air, then particles of air will be displaced both rightward and leftward as the energy of the sound wave passes through it. The motion of the particles is parallel (and anti-parallel) to the direction of the energy transport. This is what characterizes sound waves in air as longitudinal waves.Because of the longitudinal motion of the air particles, there are regions in the air where the air particles are compressed together and other regions where the air particles are spread apart. These regions are known as compressions and rarefactions respectively. The compressions are regions of high air pressure while the rarefactions are regions of low air pressure.The wavelength of a wave is merely the distance that a disturbance travels along the medium in one complete wave cycle. Since a wave repeats its pattern once every wave cycle, the wavelength is sometimes referred to as the length of the repeating patterns - the length of one complete wave. For a transverse wave, this length is commonly measured from one wave crest to the next adjacent wave crest or from one wave trough to the next adjacent wave trough. Since a longitudinal wave does not contain crests and troughs, its wavelength must be measured differently.A longitudinal wave consists of a repeating pattern of compressions and rarefactions. Thus, the wavelength is commonly measured as the distance from one compression to the next adjacent compression or the distance from one rarefaction to the next adjacent rarefaction.Since a sound wave consists of a repeating pattern of high-pressure and low-pressure regions moving through a medium, it is sometimes referred to as a pressure wave. If a detector, whether it is the human ear or a man-made instrument, were used to detect a sound wave, it would detect fluctuations in pressure as the sound wave impinges upon the detecting device. At one instant in time, the detector would detect a high pressure; this would correspond to the arrival of a compression at the detector site.At the next instant in time, the detector might detect normal pressure. And then finally a low pressure would be detected, corresponding to the arrival of a rarefaction at the detector site. The fluctuations in pressure as detected by the detector occur at periodic and regular time intervals. Sound waves traveling through air are indeed longitudinal waves with compressions and rarefactions. As sound passes through air (or any fluid medium) the particles of air do not vibrate in a transverse manner. Do not be misled - sound waves traveling through air are longitudinal waves. Characteristics of sound waves A sound wave has the same characteristics as any other type of waveform which includes wavelength, frequency, velocity and amplitude. Wavelength Wavelength is the distance from one crest to another of a wave. Since sound is a compression wave, the wavelength is the distance between maximum compressions. Speed or velocity The sound waveform moves at approximately 344 meters/second, 1130 feet/sec. or 770 miles per hour at room temperature of 20oC (70oF). Frequency The frequency of sound is the rate at which the waves pass a given point. It is also the rate at which a guitar string or a loudspeaker vibrates.The relationship between velocity, wavelength and frequency is:Velocity = wavelength x frequency Amplitude Since sound is a compression wave, its amplitude corresponds to how much the wave is compressed, as compared to areas of little compression. Thus, it is sometimes called pressure amplitude. REDOX REACTIONS Here, we will discuss about the different definitions of oxidation and reduction (redox) in terms of oxygen transfer, hydrogen and electrons. We will as well talk about oxidizing agent and reducing agent.Definitions of oxidation and reduction in terms of oxygen transfer• Oxidation is addition of oxygen.• Reduction is removal of oxygen.For instance, in the extraction of iron from its ore:Due to the fact that reduction and oxidation are going on side-by-side, this is known as a redox reaction meaning oxidation-reduction reaction. Oxidising and reducing agents An oxidizing agent is a substance that oxidizes another thing else. In the example above, the iron (III) oxide is the oxidizing agent.A reducing agent is a substance that reduces something else. In the above equation, the carbon monoxide is acting as the reducing agent.• Oxidizing agents provide oxygen to another substance.• Reducing agents take out oxygen from another substance.Oxidation and reduction in terms of hydrogen transfer• Oxidation is the loss of hydrogen from a compound.• Reduction is gain of hydrogen by a compound.These definitions you would notice are precisely the reverse of the definition of oxidation and reduction in terms of oxygen.For instance, ethanol can be oxidized to ethanal:In other to remove the hydrogen from the ethanol, you would need to make use of oxidizing agent. A regularly used oxidizing agent is potassium dichromate (VI) solution that is acidified with dilute sulphuric acid.Ethanal can as well again be reduced back to ethanol through the addition of hydrogen to it. A potential reducing agent is sodium tetrahydridoborate, NaBH4. Again, the equation is excessively complex to be worth troubling about at this level.As a summary:• Oxidizing agents provide oxygen to a different substance or take away hydrogen from it.• Reducing agents take away oxygen from another substance or provide hydrogen to it.Oxidation and reduction in terms of electron transfer• This is simply the most significant application of the oxidation and reduction at A’ level.• Oxidation is defined as electron loss.• Reduction is defined as electron gain.It is necessary that you have these definitions in mind. There is a extremely simple way to accomplish this.An example is shown below:The equation illustrates an uncomplicated redox reaction which can perceptibly be explained in terms of oxygen transfer.Copper (II) oxide and magnesium oxide are mutually ionic. The metals evidently are not. If you rephrase this as an ionic equation, it turns out that the oxide ions are bystander ions that you are left with:A last remark on oxidizing and reducing agentsIn the equation above, the magnesium is reducing the copper (II) ions by donating electrons to them to neutralize the charge. Magnesium is acting as a reducing agent.Looked at in another way, the copper (II) ions are extracting electrons from the magnesium to generate the magnesium ions. The copper (II) ions are working as an oxidizing agent. Oxidizing and Reducing Agents An oxidizing agent or oxidant is a substance that gains electrons and is reduced in a chemical reaction. The oxidizing agent is also known as electron acceptor, the oxidizing agent is usually in one of its top probable oxidation states due to the fact that it will gain electrons and be reduced. Examples of oxidizing agents are halogens, potassium nitrate, and nitric acid.A reducing agent or reductant is a substance that loses electrons and is oxidized in a chemical reaction. A reducing agent is normally in one of its lesser possible oxidation states and is referred to as the electron donor. A reducing agent would normally be oxidized due to the fact that it loses electrons in the redox reaction. Examples of reducing agents are the earth metals, formic acid, and sulfite compounds.A reducing agent reduces other substances and loses electrons; consequently, its oxidation state will amplify. An oxidizing agent oxidizes other substances and gains electrons consequently; its oxidation state will lessen.How to balance Oxidation-Reduction EquationsTrial-and-error approaches to balancing chemical equations entails playing with the equation amending the ratio of the reactants and products till the objectives below have been attained.Objectives for Balancing Chemical Equations1. The number of atoms of every element on both sides of the equation is identical and as a result mass is conserved.2. The sum of the positive and negative charges ought to be the same on both sides of the equation and consequently charge is conserved. Charge is conserved due to the fact that electrons are neither created nor destroyed in a chemical reaction.There are two scenarios where depending on trial and error can put you into trouble. Sometimes, the equation is extraordinarily complex to be calculated by trial and error within a realistic amount of time. Think about the following reaction, for instance.3 Cu(s) + 8 HNO3(aq) 3Cu2+(aq) + 2 NO(g) + 6 NO3-(aq) + 4 H2O(l)Sometimes, more than a single equation can be printed that looks as it is balanced. The subsequent equations are just a handful of the balanced equations that can be written for the reaction between the permanganate ion and hydrogen peroxide, for instance.2 MnO4-(aq) + H2O2(aq) + 6 H+(aq) 2 Mn2+(aq) + 3 O2(g) + 4 H2O(l) 2 MnO4-(aq) + 3 H2O2(aq) + 6 H+(aq) 2 Mn2+(aq) + 4 O2(g) + 6 H2O(l) 2 MnO4-(aq) + 3 H2O2(aq) + 6 H+(aq) 2 Mn2+(aq) + 5 O2(g) + 8 H2O(l) 2 MnO4-(aq) + 7 H2O2(aq) + 6 H+(aq) 2 Mn2+(aq) + 6 O2(g) + 10 H2O(l)Equations like these ought to be balanced by an additional methodical approach than trial and error. Eletrochemical cells Galvanic and Electrolytic Cells Oxidation-reduction reaction or redox reactions occur in electrochemical cells. There are two different kinds of electrochemical cells. Spontaneous reactions take place in galvanic (voltaic) cells; non-spontaneous reactions take place in electrolytic cells. The two types of cells have electrodes where the oxidation and reduction reactions take place. Oxidation takes place at the electrode referred the anode and reduction takes place at the electrode known as the cathode. Electrodes and Charge The anode of an electrolytic cell is positive electrode while cathode is negative electrode, since the anode pull anions towards you from the solution. Nevertheless, the anode of a galvanic cell is negatively charged, since the spontaneous oxidation at the anode is the basis of the cells electrons or negative charge. The cathode of a galvanic cell is its positive pole. In the 2cells- galvanic and electrolytic cells, oxidation occurs at the anode and electrons movement is from the anode to the cathode. Galvanic or Voltaic Cells The redox or reduction-oxidation reaction in a galvanic cell is a spontaneous reaction. Therefore, galvanic cells are normally used as batteries. Galvanic cell reactions provide energy which is utilized to carry out work. The energy is harvested by positioning the oxidation and reduction reactions in different containers, connected by an apparatus that permits electrons to flow. A widespread galvanic cell is the Daniell cell, illustrated below. Electrolytic Cells The redox reaction or reduction-oxidation reaction in an electrolytic cell is non spontaneous. Electrical energy is needed to stimulate the electrolysis reaction. A sample of an electrolytic cell is illustrated below with a molten NaCl that is electrolyzed to form liquid sodium and chlorine gas. The sodium ions wander toward the cathode, the electrode at which they are reduced to sodium metal. Likewise, chloride ions move to the anode and are oxidized to form chlorine gas. This sort of cell is used to generate sodium and chlorine. The chlorine gas can be gathered near the cell. The sodium metal is less heavy than the molten salt and is therefore taken away as it floats to the apex of the reaction container.Electrolysis is the passage of a direct electric current through an ionic compound that is either in molten form or dissolved in an appropriate solvent, leading to chemical reactions at the electrodes and disconnection of materials.The major components necessary to attain electrolysis are :• An electrolyte : An electrolyte is a substance that contains free ions that are the carriers of electric current in the electrolyte. If the ions are not in motion like in a solid salt electrolysis cannot take place.• A direct current (DC) supply: makes available the energy required to generate or discharge the ions in the electrolyte. Electric current is carried by electrons in the external circuit.• Two electrodes: Electrodes are electrical conductor that produces the physical boundary between the electrical circuit making available the energy and the electrolyte.Electrodes of metal, graphite and semiconductor substance are extensively used. Selection of appropriate electrode depends on chemical reactivity between the electrode and electrolyte and the asking price of production. Process of electrolysis The main process of electrolysis is the substitution of atoms and ions through the removal or addition of electrons from the external circuit. The preferred products of electrolysis are frequently in a dissimilar physical state from the electrolyte and can be separated by a number of physical processes. For instance, in the electrolysis of brine that yields hydrogen and chlorine, the resulting product are gaseous. These gaseous products bubble from the electrolyte and are collected.2 NaCl + 2 H2O → 2 NaOH + H2 + Cl2A liquid containing mobile ions (electrolyte) is manufactured by:• Solvation or reaction of an ionic compound with a solvent like water to give rise to mobile ions.• An ionic compound is dissolved or merged by heatingAn electrical potential is applied crosswise a pair of electrodes engrossed in the electrolyte.Every one of the electrodes attracts ions that have differing charge. Positively charged ions (cations) move towards the electron-supplying (negative) cathode, while negatively charged ions (anions) drift towards the positive anode.At the electrodes, electrons are taken or given out by the atoms and ions. Those atoms that gain or lose electrons to turn into charged ions move into the electrolyte. Those ions that gain or lose electrons to turn into uncharged atoms split from the electrolyte. The production of uncharged atoms from ions is referred to as discharging.The energy that is needed to make the ions to travel to the electrodes, and the energy to result to the change in ionic state, is made available by the external supply of electrical potential. Oxidation and reduction at the electrodes Oxidation of ions or neutral molecules takes place at the anode, and the reduction of ions or neutral molecules takes place at the cathode. For instance, it is probable to oxidize ferrous ions to ferric ions at the anode:Fe2+ aq → Fe3+ aq + e-It is as well likely to reduce ferricyanide ions to ferrocyanide ions at the cathode:Fe(CN)3-6 + e– → Fe(CN)4-6
Posted on: Sat, 18 Oct 2014 17:37:27 +0000
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