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Kinetics Study on the Reaction between Sodium Thiosulphate and Hydrochloric Acid

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.  

Importance of Light in Photosynthesis

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…

To Study Physical Properties of Soil

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

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.  

Paper Chromatography

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….

Tests for Ammonium Ion

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.  

Helical Spring

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

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…

Role of Carbon dioxide During Respiration

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…

Boiling Point of Water

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 of a Liquid

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…

Tests for Amines

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.  

Refractive Index of a Liquid

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…

Detection of Bile Salt in Urine

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.  …

Chemical Tests for Acetate

Acetate is a negative ion or an anion with chemical formula CH3COO-. The neutral molecules formed by the combination of the acetate ion and a cation are commonly called as acetates. The most well known compound containing acetate ion is acetic acid. Other examples of acetate salts are sodium acetate, potassium acetate etc.   This video explains how to test the presence of acetate ion in a given salt.  

Laws of Reflection of Sound

Reflection is the change in direction of a wave front at an interface between two different media so that the wave front returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. When sound travels in a given medium, it strikes the surface of another medium and bounces back in some other direction, this phenomenon is called the reflection of sound. The waves are called the incident and reflected sound waves.   This video explains how to verify the laws of reflection of sound.  

Properties of Acetic Acid

Acetic acid is an organic acid with the formula CH3-COOH. Its functional group is carboxylic acid group. Acetic acid is a monocarboxylic acid because it contains only one COOH group. It has a sour taste and pungent smell. It is the main component of vinegar. Vinegar is typically 3-7% solution of acetic acid in water. Vinegar is mainly used as a preservative in food and in the pickling of vegetables. The water free acetic acid is known as glacial acetic acid.   This video explains how to study the following properties of acetic acid (ethanoic acid): (a) Odour, (b) Solubility…

Embryo of Dicot Seeds

A seed is a small embryonic plant enclosed inside a seed coat. It is the ripened and fertilised ovule of gymnospermic and angiospermic plants. The embryo is an undeveloped plant inside a seed from which a new plant develops. All seeds do not have the same size, shape and colour. Plant embryos in seeds have structures called cotyledons. A cotyledon is the central portion of a seed embryo to which the epicotyls- the immature shoot, and the radicle- the immature roots, are attached. Plants are classified according to the number of cotyledons present in the embryo. If the embryo has…

Qualitative Analysis of Carbohydrates

Carbohydrates are most abundant organic compounds found in living organisms and are composed of carbon, hydrogen and oxygen. Carbohydrates act as the primary source to provide energy for functioning of living organisms. These are called carbohydrates because they can be considered as hydrates of carbon. Generally carbohydrates are defined as polyhydroxy aldehydes or polyhydroxy ketones or the compounds which produces such products on hydrolysis. Carbohydrates are called saccharides. Some of them have sweet taste and are called sugars.   This video explains some simple tests of carbohydrates.  

Plant and Animal Tissues

A group of cells having common origin, similar structure and performing a definite function is called a tissue. Tissues are found in plants and animals. Plant tissues can be grouped into two basic types: meristematic and permanent tissues. Parenchyma and Sclerenchyma are permanent tissues. Animal tissues can be grouped into four basic types: epithelial, muscular, connective and nervous tissues. Different tissues have distinctive architecture best suited for what they do.   This video describes how to identify Plant tissues (parenchyma and sclerenchyma) and Animal tissues (striated (striped) muscle fibres and nerve cells) from the prepared slides.  

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