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Detection of Starch in Food Samples

Starch is the most common carbohydrate in the human diet and is contained in many staple foods. The major sources of starch intake worldwide are cereals (rice, wheat, and maize) and root vegetables (potatoes and cassava). We can use iodine solution to test for the presence of starch. If starch is present is a food item, it turns blue-black colour when iodine solution is added to it.   This video explains how to test for the presence of starch in a given food sample.  

Distinguishing Between Solutions

A Solution is a Homogeneous mixture of two or more substances. The component that is present in the larger amount is called the solvent and that in smaller quantity is called the solute. Solutions are classified into three types based on their properties. •True solution: It is a homogeneous mixture of solute and solvent. •Suspension: It is a heterogeneous mixture of large particles. •Colloids :In colloids, the particles are uniformly distributed throughout the solution.   This video explains how to prepare and distinguish between true solution, suspension and colloid on the basis of their transparency, filtration criterion and stability.  

Chemical Tests for Iodide

Iodides are inorganic salts containing iodide ion, which is one of the largest monoatomic anions. In iodides, iodine is present in the formal oxidation state -1. In our daily life, iodide in encountered as a component of iodized salt. One important salt of iodide ion is silver iodide, which is highly photosensitive and widely used in photography.   This video explains how to test the presence of iodide ion in a given salt.  

Tests for Strontium Ion

Strontium is a chemical element with symbol Sr. It is a soft grey silvery metal. It is found in various salts like Strontium chloride, Strontium nitrate and Strontium carbonate as Sr2+ ion. In group V, Strontium ions are precipitated as their carbonates by adding ammonium carbonate to their solution. Strontium ion reacts with ammonium sulphate to form a white precipitate o strontium sulphate and it also imparts crimson red colour to the flame.   This video explains how to test the presence of Strontium ion in a given salt.  

Ohm’s Law and Resistance

According to the Ohm’s law, “The current flowing through a conductor is directly proportional to the potential difference across its ends provided the physical conditions (temperature, dimensions, pressure) of the conductor remains the same.” If I be the current flowing through a conductor and V be the potential difference across its ends, then according to Ohm’s Law, I α V.   This video explains how determine the resistance per cm of a given wire by plotting a graph of potential difference versus current.  

Determination of EMF of a Cell

The device which produces electrical energy from chemical reaction is called electrochemical cell. The best example of an electrochemical cell is the Daniell cell in which copper and zinc electrodes are immersed in a solution of copper sulfate zinc sulfate respectively. Here zinc acts as anode and copper acts as cathode. Potential difference between the two electrodes is called cell potential or emf of the cell. It is measured in volts.   This video explains how to study the variation of EMF in the zinc – copper electrochemical cell with change in concentration of electrolytes at room temperature.  

Force Required to Move a Wooden Block

According to Newton’s Second Law of Motion, the force acting on a body is directly proportional to the product of the mass of the body and the acceleration produced in the body by the application of the force. The acceleration takes place in the direction in which the force acts. Newton’s Second Law of Motion precisely explains the relationship between force and acceleration.   This video explains how to establish relationship between weight of a rectangular wooden block lying on a horizontal table and the minimum force required to just move it using a spring balance.  

Tests for Nickel Ion

Nickel is a chemical element with symbol Ni and atomic number 28. The most common oxidation state of nickel is +2, but compounds of Ni (0), Ni (I), and Ni (III) are well known. It is found in various salts like Nickel chloride, Nickel nitrate and Nickel carbonate as Ni (II) ion. Nickel ions are precipitated as their sulphides by passing hydrogen sulphide gas through their solution. Nickel (II) ions react with dimethylglyoxime to form bright rose-red coloured Nickel-Dimethylglyoxime complex and they react with excess of NaOH and bromine water to form a black precipitate of Nickelic hydroxide.   This…

Kinetics Study on the Reaction between Iodide Ions and Hydrogen Peroxide

The speed of a reaction or the rate of a reaction is defined as the change in concentration of a reactant or product in unit time. It can be expressed as, the rate of decrease in concentration of any one of the reactants or the rate of increase in concentration of anyone of the products. The speed of a reaction or the rate of a reaction is defined as the change in concentration of a reactant or product in unit time. It can be expressed as, the rate of decrease in concentration of any one of the reactants or the…

Single Displacement Reaction

Displacement reaction is a chemical reaction in which a more reactive element displaces a less reactive element from its compound. Both metals and non-metals take part in displacement reaction. An example of a single replacement reaction is the reaction of iron nails with copper sulphate solution. An important thing to remember with single displacement reaction is that elements that form cations can only displace cations and elements that form anions can only displace anions. There are two types of single displacement reactions : (a) Cation Replacement Reaction and (b) Anion Replacement Reaction. In cation replacement reaction, one cation replaces another…

Qualitative Analysis of Proteins

Protein is an important macronutrient essential for survival. They are constituent of calls and hence are present in all living bodies. 10-35% of calories should come from protein. Protein is found in meats, poultry, fish, meat substitutes, cheeses, milk etc. Proteins are large biological molecules composed of α-amino acids (Amino acid in which amino group is attached to α-carbon, which exist as zwitterions and are crystalline in nature). They contain carbon, hydrogen, oxygen, nitrogen and sometimes phosphorus and sulphur.   This video explains some simple tests of proteins.  

Tests for Copper (II) ion

Copper is a chemical element with the symbol Cu. It is found in many salts like copper sulphate, copper chloride and copper carbonate as Copper (II) ion. In group II, copper (II) ions are precipitated as their sulphides by passing hydrogen sulphide gas through their solution. Copper (II) ions produce a deep blue coloured complex on reaction with ammonium hydroxide and the blue coloured complex then reacts potassium ferrocyanide to form a chocolate brown precipitate of copper ferrocyanide.   This video explains how to test for the presence of copper (II) ion in a given salt.  

Adaptation In Animals

Animals are multicellular organisms that are made up of eukaryotic cells and come under the kingdom Animalia. They have a well developed sensitive nervous systems and the ability of locomotion. Animals need to ingest other organisms, or their products, for sustenance because they do not perform photosynthesis. Animals are adapted to the conditions of the habitats in which they live. There are three major types of habitat: (a)Terrestrial (land) (b)Aquatic (water) (c) Aerial or arboreal (air or tree). Animals also depend on their physical features to help them move about, obtain food, and keep safe. These physical features are called…

Relative Reactivity of Metals

Metals are elements and are good conductors of heat and electricity. Most of the metals are electropositive in nature and the metal atoms lose electrons in chemical reactions to form cations. The more reactive a metal, the greater tendency it has to form a positive ion in a chemical reaction. A more reactive metal readily reacts with other elements. The most reactive metals will react even with water while the least reactive metals will not react even with acid.   This video explains the action of Zn, Fe, Cu and Mg metals on the solutions of copper sulphate, zinc sulphate…

AC Sonometer

A sonometer is an apparatus used to study the transverse vibrations of stretched strings. It is in the form of a hollow wooden rectangular box. On the wooden rectangular box there are two bridges and a pulley at one end. A wire string is attached to one end of the wooden box, run over the bridges and pulley and carries a weight hanger at the free end. A sonometer is used to determine the frequency of alternating current. A step down transformer is used for the determination of frequency of A.C. because the voltage of the A.C. mains is 220V,…

Tests for the Calcium Ion

Calcium is a soft gray alkaline earth metal with symbol Ca. It is found in various salts like calcium chloride, calcium nitrate and calcium carbonate as Ca2+ ion. In group V, calcium ions are precipitated as their carbonates by adding ammonium carbonate to their solution. Calcium ion reacts with ammonium oxalate to form a white precipitate o calcium oxalate and it imparts brick red colour to the flame.   This video explains how to test for the presence of calcium ion in a given salt.  

Chemical Tests for Sulphite

Sulphites are compounds containing sulphite ions. In sulphite ion, the sulphur atom is doubly bonded to one oxygen atom and singly bonded to other two oxygen atoms. There is also a non-bonded lone pair of electrons on the sulphur. Sulphites are often used as preservatives in dried fruits, preserved radish and dried potato products.   This video explains how to test the presence of sulphite ion in a given salt.  

Decomposition Reaction

Decomposition is a type of chemical reaction and it may be defined as the reaction in which a single compound splits into two or more simple substances under suitable conditions. It is just the opposite of the combination reaction. The digestion of food in our body is accompanied by a number of decomposition reactions. There are three types of decomposition reactions : Thermal, Electrolytic and Photo decomposition reactions. Thermal decomposition is a chemical reaction where a single substance breaks into two or more simple substances when heated. Electrolytic decomposition may result when electric current is passed through an aqueous solution…

Tests for Magnesium Ion

Magnesium is a chemical element with symbol Mg. It is found in various salts like magnesium chloride and magnesium sulphate as Mg2+ ion. In group VI, magnesium ions form a precipitate of magnesium ammonium phosphate with ammonium phosphate solution. Magnesium ions react with ammonium phosphate in presence of ammonium chloride and ammonium hydroxide to form white precipitate of magnesium ammonium phosphate.   This video explains how to test for the presence of magnesium ion in a given salt.  

Chemical Tests for Carbonate

In chemistry, carbonate is an inorganic salt, characterized by the presence of carbonate ion, in which a carbon atom is surrounded by three oxygen atom in a triangular planar manner. Carbonate minerals are found in sedimentary rocks. The most common is calcite, the main component of limestone. Salts of carbonates like sodium carbonate and potassium carbonate are used for cleaning and preservation, as well as for the manufacturing of glass.   This video explains how to test the presence of carbonate ion in a given salt.  

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