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…
Viscosity is the property of a fluid by virtue of which an internal resistance comes into play when the liquid is in motion, and opposes the relative motion between its different layers. Thus, it is the resistance of a fluid to flow. When liquid flows over flat surface, a backward viscous force acts tangentially to every layer. This force depends upon the area of the layer, velocity of the layer, and the distance of the layer from the surface. This video explains how to determine the coefficient of viscosity of a given viscous liquid by measuring terminal velocity of…
Amines are derivatives of ammonia in which one or more hydrogen atoms are replaced by alkyl or aryl groups. When one of the three hydrogen atoms is replaced by alkyl or aryl group, primary amine is formed. When two of the three hydrogen atoms are replaced by alkyl or aryl group, secondary anime is formed. When all the three hydrogen atoms are replaced by alkyl or aryl substituents, tertiary amine is formed. This video explains some simple tests of amines.
In optics, the refractive index or index of refraction ‘n’ of a material is a dimensionless number that describes how light propagates through that medium. If ‘i’ is the angle of incidence of a ray in vacuum (angle between the incoming ray and the perpendicular to the surface of a medium, called the normal) and ‘r’ is the angle of refraction (angle between the ray in the medium and the normal), the refractive index ‘n’ is defined as the ratio of the sine of the angle of incidence to the sine of the angle of refraction. This video explains…
Bile is a yellow-green fluid that contains water and organic molecules such as cholesterol, bile acids, and bilirubin. In humans, the two main function of bile are digestion and absorption of fats and eliminating bile salts from the body by secretion into bile. Adult humans produce around 400 to 800 ml of bile daily. In humans and most vertebrates, bile is produced by the liver. The gall bladder holds the bile produced in the liver and when the organism eats, bile is discharged into the duodenum. The formation of bile salts starts with the breakdown of red blood cells. …