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A mixture is a substance made by combining two or more different materials in such a way that no chemical reaction occurs. A mixture can usually be separated back into its original components.   Most natural substances are mixtures. eg:Graphite   A homogeneous mixture has the same uniform appearance and composition throughout. Many homogeneous mixtures are commonly referred to as solutions. A heterogeneous mixture consists of visibly different substances or phases. The three phases or states of matter are gas, liquid, and solid.  

Elements and Compounds

An element is a single type of atom, while a compound consists of two or more types of atoms. Elements cannot be further divided into smaller units without using large amounts of energy. Compounds, meanwhile, can often have their bonds broken using reasonable amounts of energy, such as heat from a fire. Examples of elements : gold, copper, carbon, and oxygen. Example of compound :Table salt, i.e., sodium chloride (NaCl), a compound that is composed of elements sodium (Na) and chlorine (Cl).  

Atoms and Molecules

Atoms are the smallest particle into which an element can be divided. Atoms can join together to form molecules, which in turn form most of the objects around you.   Atoms are composed of particles called protons, electrons and neutrons. Protons carry a positive electrical charge, electrons carry a negative electrical charge and neutrons carry no electrical charge at all. The protons and neutrons cluster together in the central part of the atom, called the nucleus, and the electrons ‘orbit’ the nucleus. A particular atom will have the same number of protons and electrons and most atoms have at least…

Interconversion of States of Matter

Another important physical property of matter is phase. The three most common phases of matter are solids, liquids, and gases. Water can exist in the solid, liquid, or gas phase.   Examples of phase changes include melting, freezing, condensation, evaporation, and sublimation. Melting occurs when a solid changes to a liquid. Freezing occurs when a liquid becomes a solid. Condensation involves a gas becoming a liquid. Evaporation involves a liquid becoming a gas and sublimation is the change of a solid directly to a gas. Phase changes require either the addition of heat energy (melting, evaporation, and sublimation) or subtraction…

States of Matter

Matter is anything made of atoms and molecules. Matter is anything that has mass and takes up space.   All matter exists as solids, liquids, or gases. These are called the states of matter. Matter can change from one state to another if heated or cooled. If ice (a solid) is heated it changes to water (a liquid). This change is called MELTING. If water is heated, it changes to steam (a gas). This change is called BOILING. The particles of ice, water, and steam are identical, but arranged differently.  

Thomson’s Model of an Atom

In 1897, J.J. Thomson discovered the electron, the first subatomic particle.   In 1904, Thomson proposed atomic model where electrons are embedded within spherically distributed, positive charge (so-called “plum pudding” model).Both the positive charge and the mass of the atom would be more or less uniformly distributed over its size.  

Chemical Reactions

In a chemical change, chemical reaction takes place and the substances undergo a change in their state. During chemical reactions, one substance reacts with another to form a new substance. The chemical composition of the new substance is different from that of the reacting species. Due to a chemical change, the chemical properties of matter also change. That means the product is entirely different from either of the reactants. Some chemical reactions may be either exothermic or endothermic in nature. In endothermic reactions, a substance absorbs energy in the form of heat and undergoes a chemical reaction. In exothermic reactions,…

Separation of Mixtures using Different Techniques

In chemistry, a mixture is a material system made up of two or more different substances which are mixed but are not combined chemically. Mixtures come in many forms and phases. Most of them can be separated, and the kind of separation method depends on the kind of mixture it is. Some common separation methods are: Simple distillation, fractional distillation, Separating funnel, centrifugation and Paper Chromatography. Simple distillation and fractional distillation are best for separating a solution of two miscible liquids. Fractional distillation is most suitable for separation of a mixture of two or more miscible liquids for which the…

Properties of Acids and Bases

The word acid comes from the Latin word acere, which means “sour.” All acids taste sour. Well known from ancient times were vinegar, sour milk and lemon juice. Acids produce hydrogen ion (H+) in solution and make a blue vegetable dye called litmus turn red. Upon chemically reacting with an active metal, acids will evolve hydrogen gas. Another common acid reaction some sources mention is that acids react with carbonates (and bicarbonates) to give carbon dioxide gas.   Bases are substances which will restore the original blue color of litmus after having been reddened by an acid. All bases taste…

Basic Laboratory Techniques

Laboratory experiment is an important part in chemistry which required a good observation and utilization of right laboratory technique. In a chemical laboratory we carry out some simple operations like bending or cutting a glass tube, boring a cork and studying the complex process of analyzing substances qualitatively and quantitatively.   This video explains some basic laboratory techniques.  

Purification of Impure Samples by Crystallization

Crystallization is a method of purifying a solid. There are two types of impurities: those more soluble in a given solvent than the main component and those less soluble. The crystallization process itself helps in the purification because as the crystals form, they select the correct molecules, which fit into the crystal lattice and ignore the wrong molecules. The solubility of the compound in the solvent used for crystallization is important. This is of course not a perfect process, but it does increase the purity of the final product.   This video explains how to prepare the crystals of (a)…

Detection of Elements: Lassaigne’s Test

The sodium fusion test, or Lassaigne’s test, is used in elemental analysis for the qualitative determination of the presence of foreign elements, namely halogens, nitrogen, and sulphur, in an organic compound. It was developed by J. L. Lassaigne. The compound is heated with sodium metal to convert the elements present in the organic compound into the water-soluble salts of sodium. Sodium is fused with the organic compound and then the fused mass is extracted with water. The extract is filtered and the filtrate is called sodium extract or Lassaigne’s extract. Nitrogen, if present in the compound, is converted into NaCN…

Preparation of Lyophilic and Lyophobic Sols – MeitY OLabs

Colloids are the dissolved state of substances that either do not pass, or pass very slowly through a parchment paper or animal membrane. If colloids have strong affinity between particles of dispersed phase and dispersion medium, they are called as lyophilic sols. Lyophilic sols are reversible in nature. They can be prepared again by simply mixing the dispersion medium with the dispersion phase and shaking the mixture. Lyophobic sols are those in which the dispersed phase has no attraction for the dispersion medium or the solvent. Their colloidal sols can be prepared only by special methods and they are irreversible…

Tests for the Functional Group Present in the Organic Compounds

Inorganic compounds are substances that do not come from living things. They are formed by non-living natural processes or by laboratory preparation methods. The branch of chemistry that deals with the behaviour and properties of inorganic compounds is called Inorganic Chemistry. Inorganic compounds are found in nature in the form of minerals. The two important classes of inorganic compounds are Coordination Compounds and Double Salts. Complex compounds are formed by a large number of transition metals in which the metal atom is bound to neutral molecules or to negatively charged species called ligands. Double salts are compounds that contain more…

Qualitative Analysis of Carbohydrates

Molecules of organic compounds except that of hydrocarbons can be divided into two parts, a reactive part which is referred to as functional group and a skeleton of carbon atoms called alkyl group. The properties of a compound are largely determined by the functional group. Different compounds having same functional group have similar properties and are classified as family of compounds, Compounds having different functional groups have different properties and belong to different families of compounds.   This video explains how to identify the functional groups present in an organic compound.  

Determination of Concentration of KMnO4 Solution

Potassium permanganate is a strong oxidizing agent. Permanganate is an intense dark purple color. Reduction of purple permanganate ion to the colorless manganese ion, the solution will turn from dark purple to a faint pink color at the equivalence point. No additional indicator is needed for this titration. The reduction of permanganate requires strong acidic conditions.   This video explains how to determine the concentration of potassium permanganate solution by titrating it against a standard solution of (a) Oxalic acid and (b) Ferrous ammonium sulphate (Mohr’s salt).  

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