The word acid comes from the Latin word acere, which means “sour.” All acids taste sour. Well known from ancient times were vinegar, sour milk and lemon juice. Acids produce hydrogen ion (H+) in solution and make a blue vegetable dye called litmus turn red. Upon chemically reacting with an active metal, acids will evolve hydrogen gas. Another common acid reaction some sources mention is that acids react with carbonates (and bicarbonates) to give carbon dioxide gas. Bases are substances which will restore the original blue color of litmus after having been reddened by an acid. All bases taste…
Laboratory experiment is an important part in chemistry which required a good observation and utilization of right laboratory technique. In a chemical laboratory we carry out some simple operations like bending or cutting a glass tube, boring a cork and studying the complex process of analyzing substances qualitatively and quantitatively. This video explains some basic laboratory techniques.
Crystallization is a method of purifying a solid. There are two types of impurities: those more soluble in a given solvent than the main component and those less soluble. The crystallization process itself helps in the purification because as the crystals form, they select the correct molecules, which fit into the crystal lattice and ignore the wrong molecules. The solubility of the compound in the solvent used for crystallization is important. This is of course not a perfect process, but it does increase the purity of the final product. This video explains how to prepare the crystals of (a)…
The sodium fusion test, or Lassaigne’s test, is used in elemental analysis for the qualitative determination of the presence of foreign elements, namely halogens, nitrogen, and sulphur, in an organic compound. It was developed by J. L. Lassaigne. The compound is heated with sodium metal to convert the elements present in the organic compound into the water-soluble salts of sodium. Sodium is fused with the organic compound and then the fused mass is extracted with water. The extract is filtered and the filtrate is called sodium extract or Lassaigne’s extract. Nitrogen, if present in the compound, is converted into NaCN…
Colloids are the dissolved state of substances that either do not pass, or pass very slowly through a parchment paper or animal membrane. If colloids have strong affinity between particles of dispersed phase and dispersion medium, they are called as lyophilic sols. Lyophilic sols are reversible in nature. They can be prepared again by simply mixing the dispersion medium with the dispersion phase and shaking the mixture. Lyophobic sols are those in which the dispersed phase has no attraction for the dispersion medium or the solvent. Their colloidal sols can be prepared only by special methods and they are irreversible…
Inorganic compounds are substances that do not come from living things. They are formed by non-living natural processes or by laboratory preparation methods. The branch of chemistry that deals with the behaviour and properties of inorganic compounds is called Inorganic Chemistry. Inorganic compounds are found in nature in the form of minerals. The two important classes of inorganic compounds are Coordination Compounds and Double Salts. Complex compounds are formed by a large number of transition metals in which the metal atom is bound to neutral molecules or to negatively charged species called ligands. Double salts are compounds that contain more…
Molecules of organic compounds except that of hydrocarbons can be divided into two parts, a reactive part which is referred to as functional group and a skeleton of carbon atoms called alkyl group. The properties of a compound are largely determined by the functional group. Different compounds having same functional group have similar properties and are classified as family of compounds, Compounds having different functional groups have different properties and belong to different families of compounds. This video explains how to identify the functional groups present in an organic compound.
Potassium permanganate is a strong oxidizing agent. Permanganate is an intense dark purple color. Reduction of purple permanganate ion to the colorless manganese ion, the solution will turn from dark purple to a faint pink color at the equivalence point. No additional indicator is needed for this titration. The reduction of permanganate requires strong acidic conditions. This video explains how to determine the concentration of potassium permanganate solution by titrating it against a standard solution of (a) Oxalic acid and (b) Ferrous ammonium sulphate (Mohr’s salt).
Thermochemistry is the study of heat and energy associated with a chemical reaction or a physical transformation. A reaction may absorb or release energy. Measurement of heat changes are carried out in vessels called calorimeters. During measurement of heat changes, the calorimeter also absorbs some heat; this amount of heat should also be known. It is called calorimeter constant or water equivalent of calorimeter. To determine the water equivalent of calorimeter, known volume of hot water at a specified temperature is added to known volume of water contained in the calorimeter at room temperature. Since energy is conserved, the heat…
Organic compound, any of a large class of chemical compounds in which one or more atoms of carbon are covalently linked to atoms of other elements, most commonly hydrogen, oxygen, or nitrogen. rea was the first organic compound to be prepared in the laboratory, which was by synthesized chance. It was prepared by Friedrich Wohler, a German chemist in the year 1828. Organic synthesis is a method of preparation of organic compounds. It is concerned with the preparation of organic compounds through organic reactions. This video explains how to synthesize a sample of (a) Acetanilide from aniline (b) Dibenzal…
Resonance Column :- The velocity with which sound travels in any medium may be determined if the frequency and the wavelength are known. The relationship between these quantities is: v = fλ where v = velocity of sound propagation f = frequency λ = wavelength The wavelength of the sound will be determined by making use of the resonance of an air column. The apparatus for the experiment consists of a long cylindrical tube attached to a water reservoir. The length of the water column may be changed by raising or lowering the water level while the tuning fork…
Sound is a mechanical wave that needs a material medium like air, water, steel, etc. for its propagation. We can describe a sound wave by its frequency, wavelength and velocity. The sound wave is a longitudinal wave, i.e., the particles of the medium vibrate in a direction parallel to the direction of the propagation of the wave. Sound always originates from some vibrating body. The bell jar experiment is a common experiment used to demonstrate that sound needs a medium to travel. This video demonstrate that sound needs a material medium for its propagation.
Newton’s Second Law of motion states that the rate of change of momentum of an object is proportional to the applied unbalanced force in the direction of the force. ie., F=ma. Where F is the force applied, m is the mass of the body, and a, the acceleration produced. If a body is subjected to multiple forces at the same time, then the acceleration produced is proportional to the vector sum (that is, the net force) of all the individual forces. The Second Law can also relate the net force and the momentum of the body. Therefore, Newton’s Second Law…
The viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress. For liquids, it corresponds to the informal concept of “thickness”; for example, honey has a much higher viscosity than water. the viscosity of liquids and gases are affected by temperature but in opposite ways meaning that upon heating, the viscosity of a liquid decreases rapidly, whereas gases flow more sluggishly. There are numerous ways to measure viscosity. A more advanced design of measuring viscosity known as the Ostwald Viscometer. An Ostwald Viscometer consists of two reservoir bulbs and a capillary…
Potentiometer is a simple device used to measure the electromotive force, potential difference across a resistor and internal resistance of a cell. It consists of a board where a tungsten or manganese wire is fitted on it. The wires have uniform cross-sectional area and of 10 m in length. The wires are joined in series by using thick copper strips. A metre scale is also attached on the wooden board. It works on the principle that the potential dropped between two points in a wire of uniform cross section is directly proportional to the distance between the points. This…
The electromotive force (emf) of a cell is its terminal voltage when no current is flowing through it. The terminal voltage of a cell is the potential difference between its electrodes. A voltmeter cannot be used to measure the emf of a cell because a voltmeter draws some current from the cell. To measure a cell’s emf a potentiometer is used since in a potentiometer measurement no current is flowing. It employs a null method of measuring potential difference, so that when a balance is reached and the reading is being taken, no current is drawn from the source to…
Concave Mirror Focal Length by u-v Method :- Concave mirrors have the reflecting surface that bulges inward. They are also called converging mirrors because it converges all parallel beam of light incident on it. Unlike a flat mirror, concave mirrors can form real images that are projected out in front of the mirror at the place where the light focuses. Concave mirrors can be used in satellite dishes, vehicle headlights, astronomical telescopes and many more areas. The relation between object distance u and the image v from the pole of the mirror is given by, 1/v + 1/u = 1/f…
A convex mirror is a curved mirror in which the reflecting surface bulges towards the light source. Convex mirrors reflect light outwards; therefore they are not used to focus light. A convex mirror is also known as fish eye mirror or diverging mirror. The image formed by a convex lens is virtual and erect, since the focal point (F) and the centre of curvature (2F) are both imaginary points “inside” the mirror that cannot be reached. As a result, images formed by these mirrors cannot be projected on a screen, since the image is inside the mirror. Therefore, its focal…
A concave lens is thinner at the center that at the edges. So the light beams passing through the lens are spread out or diverged. Therefore, the concave lens is called a diverging lens. The image formed by a concave lens is virtual and diminished. Since a concave lens will not produce a real image, a convex lens is used to measure its focal length. There are two methods to find the focal length of a concave lens: (a) Lens in Contact Method and (b) Lens out of Contact Method. This video explains how find the focal length of…
Diode is a two terminal P-N junction device. P-N junction is formed by bringing a P type material in contact with N type material. Diode is unidirectional device that allows the flow of current in one direction only depending on the biasing. When P- terminal connected to positive terminal of battery and N-terminal connected to negative terminal of battery, it is said to be forward biased. In reverse biasing P- terminal is connected to negative terminal of the battery and N- terminal to positive terminal of battery. A diode characteristic is simply a graph of the voltage applied to…