Aluminium is a chemical element in the boron group with symbol Al and atomic number 13. Aluminum has three oxidation states. The most common one is +3. The other two are +1 and +2. One +3 oxidation state for Aluminum can be found in the compound aluminum oxide, Al2O3. In AlO, aluminum monoxide, it has a +2 oxidation state, and AlH has an oxidation state of +1.It is found in various salts like aluminium chloride and aluminium oxide as Al (III) ion. Aluminium ion is precipitated as its hydroxide by adding ammonium hydroxide to its solution. This video explains…
The mosquitoes are a family of small, midge-like flies. Like all flies, mosquitoes go through four stages in their life – egg, larva, pupa, and adult. We call this as the life cycle. Each of these stages is morphologically different from the other, with even the habitat of each stage differing. The first three stages – egg, larva and pupa are largely aquatic, whereas the adult stage is aerial. The eggs are laid one at a time and they float on the surface of the water. Most eggs hatch into larvae within 48 hours. Mosquito larvae live in water from…
The metre bridge, consists of a one metre long wire of uniform cross sectional area, fixed on a wooden block. A scale is attached to the block. Two gaps are formed on it by using thick metal strips in order to make the Wheat stone’s bridge. The metre bridge is operates under Wheat stone’s principle. Here, four resistors P, Q, R, and S are connected to form the network ABCD. In the balancing condition, there is no deflection on the galvanometer. Then, P/q = R/S. This video explains how to verify the laws of resistances in series and parallel….
A slinky is a long helical spring, usually made of steel. It is flexible and has appreciable elasticity. It produces transverse waves when one end is fixed and the other end is stretched and given a jerk at right angle to its length. It produces longitudinal waves when compressions are given at regular intervals of time at the free end of the slinky. A disturbance which propagates through a medium is called wave. This video explains how to determine the velocity of a pulse propagated through a slinky or a stretched string.
The Newton’s Law of Cooling is named after the famous English Physicist Sir Isaac Newton, who conducted the first experiments on the nature of cooling. According to Newton’s Law of Cooling, the rate of cooling of a body is directly proportional to the difference in temperatures of the body (T) and the surrounding (T0), provided difference in temperature should not exceed by 30 °C. This video explains how to study the relationship between the temperature of a hot body and its time of cooling by plotting a cooling curve.
Bromides are chemical compounds containing bromide ion. Bromide ion is formed when bromine atom gains an electron. The examples of bromide salts are sodium bromide, potassium bromide, cesium bromide etc. Bromide is also present in typical seawater with a concentration of around 65 mg/L. One important salt of bromide is silver bromide which is used in photographic films. This video explains how to test the presence of bromide ion in a given salt.
A chemical reaction is process by which one set of chemical substances is transformed to another. The French chemist, Antoine Lavoisier, who is known as the father of modern chemistry, proved that the mass of the products in a chemical reaction is equal to the mass of the reactants. “The Law of Conservation of Mass states that matter can neither be created nor destroyed in a chemical reaction”. This video explains how to verify the Law of Conservation of Mass during a chemical reaction.
Double displacement reactions may be defined as the chemical reactions in which one component each of both the reacting molecules get exchanged to form the products. During this reaction, the cations and anions of two different compounds switch places, forming two entirely different compounds. Double displacement reactions generally take place in aqueous solutions in which the ions precipitate and there is an exchange of ions. For example, on mixing a solution of barium chloride with sodium sulphate, a white precipitate of barium sulphate is immediately formed. These reactions are ionic in nature. The reactants changes into ions when dissolved in…
When an iron nail is dipped in copper sulphate solution, a brown coating of copper is formed on the surface of iron and the colour of copper sulphate solution changes from blue to light green. This reaction shows that iron is more reactive than copper as it displaces copper from its solution and iron passes into solution as Fe (II) ions and ferrous sulphate solution is formed. This video explains the chemical change occurs during the reaction of iron nails with copper sulphate solution.
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.