Nitrites are inorganic compounds contain nitrite ion in which nitrogen is bonded to two oxygen atoms. It is a symmetric anion with equal nitrogen – oxygen bond length and O-N-O bond angle of approximately 120 °C. Upon protonation, nitrite ion produces weak nitrous acid, which is unstable. This video explains how to test the presence of nitrite ion in a given salt.
Food is one of the essential factors in our daily life that provides nutritional support for the human body. Due to the population explosion in India the demand for food has increased and traders have started mixing cheaper substances with food. These cheaper or undesirable substances added to food are called adulterants. Metanil yellow is a principal non-permitted food colour used extensively in India. The effect of long-term consumption of metanil yellow on the developing and adult brain causes neurotoxicity. Metanil yellow is used in dal as an adulterant for colouring. Its presence can be tested in dal with the…
A Zener diode is a heavily doped silicon crystal diode which allows current to flow in the forward direction in the same manner as an ideal diode. It also permits the current to flow in the reverse direction when the voltage is above a certain value known as the breakdown voltage. Breakdown voltage is also known as Zener knee voltage. The device was named after an American Physicist, Clarence Zener, who described the property concerning the breakdown of electrical insulators. The device consists of a reverse biased, highly doped, p-n junction diode operating in the breakdown region. Conventional diodes and…
Separating funnel is used for the separation of components of a mixture between two immiscible liquid phases. One phase is the aqueous phase and the other phase is an organic solvent. This separation is based on the differences in the densities of the liquids. The liquid having more density forms the lower layer and the liquid having less density forms the upper layer. This video explains how to separate a mixture of oil and water using a separating funnel.
Sulphides are inorganic compounds of sulphur containing sulphide ions. Sulphide ion forms variety of compounds. One famous example is the bright yellow species cadmium sulphide or cadmium yellow. Also the black tarnish on sterling silver is due to the formation of silver sulphide. This video explains how to test the presence of sulphide ion in a given salt.
Sulphates are inorganic salts containing sulphate ion. Sulphate ion is a plyatomic anion in which the central sulphur atom is surrounded by four equivalent oxygen atoms in a tetrahedral arrangement. In sulphate ion, the sulphur atom is in the +6 oxidation state while the four oxygen atoms are each in the -2 states. Sulphate ion forms many salts like sodium sulphate, potassium sulphate, barium sulphate etc. The very well known coloured salts of sulphate are green vitriol and blue vitriol. This video explains how to test the presence of sulphate ion in a given salt.
Alcohols are organic compounds containing hydroxyl functional group. They are formed by replacing hydrogen atom of a hydrocarbon with a –OH group. Alcohols are classified as monohydric, dihydric and trihydric depending on the number of hydroxyl group. They are further classified as primary (1°), secondary (2°) and tertiary (3°) according to the hydroxyl group is attached to primary, secondary and tertiary carbon atoms respectively. Methyl alcohol and ethyl alcohol are the simplest alcohols. This video explains how to identify alcohols using some simple tests.
Ketones are organic compounds containing ketonic functional group, in which the carbonyl carbon is attached to two R groups. The R groups may be alkyl or aryl groups. The flavors of berries and mushrooms are due to the presence of ketones. This video explains how to identify ketones using some simple tests.
Pollination is a very important part of the life cycle of a flowering plant. Pollination is the transference of pollen grain from the anthers of a flower to the stigma of the same or another flower, mediated by abiotic or biotic means. Abiotic means the pollen is not carried by organisms, but through means such as wind or water. Biotic pollination occurs through agents like animals, insects or birds. The majority of plants are pollinated through biotic pollination. This video explains how to study pollen germination on a slide.
Fats and oils are concerted source of energy. Certain percentage of body weight of human being is fat and 20-35% of calories should come from fat. Fats in the diet are essential for good health and are needed for the growth of the body and the processing of vitamins. They make up part of all cells and help to maintain the body temperature. They form fatty tissue around delicate organs to protect them from injury.Chemically fats and oils are trimesters of glycerol and higher fatty acids. They are of animal or plant origin. Desi ghee is animal ghee while vanaspati…
Sodium thiosulphate reacts with diluted acid to give sulphur dioxide, sulphur and water. Both sodium thiosulphate and diluted hydrochloric acid are colorless solution. Sulphur dioxide is a very soluble gas and dissolves completely in the aqueous solution. The sulphur formed, however, is not soluble and will exist in the mixture as white or yellow precipitate (or colloidal). It makes the reaction mixture becomes opaque as the reaction occurs. Therefore, we can study the reaction rate by monitoring the opaqueness of the reaction. This can be easily done by measuring the time taken for forming a certain amount of precipitate.
Photosynthesis is the process in which light energy is converted into chemical energy. Using the energy of light, carbohydrates such as sugars are synthesized from carbon dioxide and water. The process of photosynthesis occurs when green plants use the energy of light to convert carbon dioxide (CO2) and water (H2O) into carbohydrates. Light energy is absorbed by chlorophyll, a photosynthetic pigment of the plant, while air containing carbon dioxide and oxygen enters the plant through the leaf stomata. An extremely important by-product of photosynthesis is oxygen, on which most organisms depend. Glucose, a carbohydrate processed during photosynthesis, is mostly used…
Soil is the upper humus, containing a layer of the earth, consisting of rock and mineral particles mixed with decayed organic matter. Soil sustains plant life and contains numerous living organisms. Soil, along with air and water, is one of the three most important natural resources, which we cannot live without. A productive soil contains approximately 46% mineral matter, 4% organic matter, 25 % water and 25% air. This video explains how to study soil for texture, moisture content, pH and water holding capacity.
Simple distillation is a method used for the separation of components of a mixture containing two miscible liquids that boil without decomposition and have sufficient difference in their boiling points. Distillation process involves heating a liquid to its boiling points, and transferring the vapors into the cold portion of the apparatus, then condensing the vapors and collecting the condensed liquid in a container. This video explains how to separate a mixture of acetone and water by simple distillation.
Chromatography is a technique used to separate molecules on the basis of differences in size, shape, mass, charge, solubility and adsorption properties. In paper chromatography, the mixture is spotted onto the paper, dried and the solvent is allowed to flow along the sheet by capillary attraction. As the solvent slowly moves through the paper, the different compounds of the mixture separate into different coloured spots. The paper is dried and the position of different compounds is visualized. The principle behind the paper chromatography is that the most soluble substances move further on the filter paper than the least soluble substances….
Ammonium ion is a positively charged polyatomic ion with formula NH4+. It is formed by the protonation of ammonia. It has tetrahedral structure. Ammonium ion is found in variety of salts such as ammonium carbonate, ammonium chloride and ammonium nitrate. When ammonium salt is heated with conc. NaOH, ammonia gas is evolved which gives white fumes of ammonium chloride with dil.HCl and a brown coloured precipitate with Nessler’s reagent. This video explains how to test the presence of ammonium ion in a given salt.
The helical spring, is the most commonly used mechanical spring in which a wire is wrapped in a coil that resembles a screw thread. It can be designed to carry, pull, or push loads. Twisted helical (torsion) springs are used in engine starters and hinges. The helical spring is suspended vertically from a rigid support. The pointer is attached horizontally to the free end of spring. A meter scale is kept vertically in such a way that the tip of the pointer is over the divisions of the scale; but does not touch the scale. Helical spring works on the…
Newton’s Third Law of Motion states: ‘To every action there is an equal and opposite reaction’. The Third Law of Motion indicates that when one object exerts a force on another object, the second object instantaneously exerts a force back on the first object. These two forces are always equal in magnitude, but opposite in direction. For example, when we placed a wooden block on the ground, this block exerts a force equal to its weight, W = mg acting downwards to the ground. This is the action force. The ground exerts an equal and opposite force W’ = mg…
Respiration is the process during which organic food, mainly glucose that is present in the cell, breaks down into simpler substances and liberates carbon dioxide and energy. The energy released during respiration is chemical energy. There are two types of respiration- aerobic and anaerobic respiration. During aerobic respiration, complete oxidation of carbohydrates takes place. Glucose is broken down by oxygen to release energy, while carbon dioxide and water are the by-products of the reaction. Aerobic respiration occurs in plants as well as animals and takes place in the mitochondria. Sometimes there is not enough oxygen around for animals and plants…
As a liquid is heated, its temperature increases and the molecules of the liquid gain energy and their kinetic energy increases. As the kinetic energy increases, the molecular motion increases and the molecules of the liquid overcome the force of attraction between them.On continuous heating, a particular temperature is reached where the molecules of the liquid leave the surface in the form of vapour to produce a pressure above the liquid equal to the atmospheric pressure and the liquid starts boiling. At this stage temperature remains stationary even on heating further. This stationary temperature at which the vapour pressure of…