Class 11 Chemistry Chapter 1 Notes Pdf Download In Hindi Medium

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Thisarticle is a continuation of the revision notes on CBSE Class 12 Chemistry: Surface Chemistry, Part-I. In Part-I, we have studied about basic concepts of Surface Chemistry like Adsorption, Absorption, Catalysis etc. Now, in this part (or Part - 2), we will study some more important topics like Colloids, Classification of colloids, Preparation of colloids etc.

The purpose of these notes is to give you a quick glance of the chapter. This article is a continuation of the revision notes on Class 12 Chemistry: Chapter 5- Surface Chemistry, Part-I. In Part-I you discovered about the concepts of Surface Chemistry, Adsorption, Absorption, Catalysis etc.

Depending upon the size of the solute particles the solutions can be categorised as true solution, suspension and colloids. The type of solution in which the size of the solute particle is in the range of 1 to 100 nm, is called a colloid. A colloid is a heterogeneous system in which one substance is dispersed (dispersed phase or colloidal particles) in another substance which is called dispersion medium.

On the basis of the physical state of the dispersed phase and the dispersion medium the colloidal solutions can be classified into eight types: Dispersed phase Dispersion medium Type of colloid Examples Solid Solid Solid sol Gem stones, Coloured glasses Solid Gas Aerosol Dust, Smoke Solid Liquid Sol Paint Liquid Liquid Emulsion Milk Liquid Solid Gel Butter, Cheese Liquid Gas Aerosol Fog, Cloud Gas Liquid Foam Froth Gas Solid Solid sol Rubber, Foam In short, if the dispersion medium is solid then the colloid is known as gel. If the dispersion medium is liquid or gas then the colloid is called sol. A colloid in which both the dispersed phase and dispersion medium are in the liquid form is known as emulsion.

(a) Lyophilic Colloids: As the name lyophilic (liquid-loving or solvent attracting) indicates, lyophilic colloids are the colloids exhibiting a strong interaction between the two phases.

The substances like gum, gelatin, starch, when mixed with a suitable liquid as the dispersion medium, directly form the colloidal sol which is also named as lyophilic sol.

(b) Lyophobic Colloids: Lyophobic' means 'liquid hating', which indicates that in these sols there is little or no interaction between the two phases. Substances like metals and their sulphides, when simply mixed with the dispersion medium do not form colloidal sol. They cannot be prepared by simply mixing the two phases. Such substances are called Lyophobic Sols.

Difference between Lyophilic sol and Lyophobic sol: Lyophilic Sol Lyophobic Sol These are reversible sols. These are irreversible sols. They are quite stable and are not easily coagulated by electrolytes. They are less stable and get coagulated by electrolytes, by heating or by agitating. They are obtained by simple solution method, e.g. starch solution. They are prepared by indirect methods which are not so easy. They are obtained from organic material such as starch, gum, gelatin etc. They are obtained from inorganic materials such as metals, sulphides, metal oxides etc. The particles are hydrated. The particles are not hydrated. Preparation of Lyophilic and Lyophobic sols:

The process of forming aggregates from colloidal particles by the addition of suitable electrolyte is called coagulation. The addition of an electrolyte to a lyophobic colloid results in its coagulation. At lower concentration of electrolyte, the aggregation of particles is called flocculation. Flocculation is reversible while coagulation is irreversible.

The emulsions are generally prepared by shaking strongly the mixture of two colloids these emulsions are generally unstable, e.g., oil and water are immiscible and form unstable emulsions. Thus a substance is added to stabilize the emulsions which named as emulsifiers or emulsifying agents.

For example: Protein casein is present in milk as an emulsifying agent.

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Chemistry is the scientific study of the properties and behavior of matter.[1] It is a physical science within the natural sciences that studies the chemical elements that make up matter and compounds made of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during reactions with other substances.[2][3][4][5] Chemistry also addresses the nature of chemical bonds in chemical compounds.

In the scope of its subject, chemistry occupies an intermediate position between physics and biology.[6] It is sometimes called the central science because it provides a foundation for understanding both basic and applied scientific disciplines at a fundamental level.[7] For example, chemistry explains aspects of plant growth (botany), the formation of igneous rocks (geology), how atmospheric ozone is formed and how environmental pollutants are degraded (ecology), the properties of the soil on the Moon (cosmochemistry), how medications work (pharmacology), and how to collect DNA evidence at a crime scene (forensics).

Chemistry has existed under various names since ancient times.[8] It has evolved, and now chemistry encompasses various areas of specialisation, or subdisciplines, that continue to increase in number and interrelate to create further interdisciplinary fields of study. The applications of various fields of chemistry are used frequently for economic purposes in the chemical industry.

The word chemistry comes from a modification during the Renaissance of the word alchemy, which referred to an earlier set of practices that encompassed elements of chemistry, metallurgy, philosophy, astrology, astronomy, mysticism, and medicine. Alchemy is often associated with the quest to turn lead or other base metals into gold, though alchemists were also interested in many of the questions of modern chemistry. [9][10]

The modern word alchemy in turn is derived from the Arabic word al-kīmīā (الكیمیاء). This may have Egyptian origins since al-kīmīā is derived from the Ancient Greek χημία, which is in turn derived from the word Kemet, which is the ancient name of Egypt in the Egyptian language.[11] Alternately, al-kīmīā may derive from χημεία 'cast together'.[12]

The current model of atomic structure is the quantum mechanical model.[13] Traditional chemistry starts with the study of elementary particles, atoms, molecules,[14] substances, metals, crystals and other aggregates of matter. Matter can be studied in solid, liquid, gas and plasma states, in isolation or in combination. The interactions, reactions and transformations that are studied in chemistry are usually the result of interactions between atoms, leading to rearrangements of the chemical bonds which hold atoms together. Such behaviors are studied in a chemistry laboratory.

The chemistry laboratory stereotypically uses various forms of laboratory glassware. However glassware is not central to chemistry, and a great deal of experimental (as well as applied/industrial) chemistry is done without it.

A chemical reaction is a transformation of some substances into one or more different substances.[15] The basis of such a chemical transformation is the rearrangement of electrons in the chemical bonds between atoms. It can be symbolically depicted through a chemical equation, which usually involves atoms as subjects. The number of atoms on the left and the right in the equation for a chemical transformation is equal. (When the number of atoms on either side is unequal, the transformation is referred to as a nuclear reaction or radioactive decay.) The type of chemical reactions a substance may undergo and the energy changes that may accompany it are constrained by certain basic rules, known as chemical laws.

Energy and entropy considerations are invariably important in almost all chemical studies. Chemical substances are classified in terms of their structure, phase, as well as their chemical compositions. They can be analyzed using the tools of chemical analysis, e.g. spectroscopy and chromatography. Scientists engaged in chemical research are known as chemists.[16] Most chemists specialize in one or more sub-disciplines. Several concepts are essential for the study of chemistry; some of them are:[17]

The atom is the basic unit of chemistry. It consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. The nucleus is made up of positively charged protons and uncharged neutrons (together called nucleons), while the electron cloud consists of negatively charged electrons which orbit the nucleus. In a neutral atom, the negatively charged electrons balance out the positive charge of the protons. The nucleus is dense; the mass of a nucleon is approximately 1,836 times that of an electron, yet the radius of an atom is about 10,000 times that of its nucleus.[19][20]

The atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state(s), coordination number, and preferred types of bonds to form (e.g., metallic, ionic, covalent).

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