Chemistry Comes Alive by examville

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									Chemistry comes alive-2

CHEMISTRY COMES ALIVE
BASIC CHEMISTRY Matter : Matter is any substance that possesses a mass and occupies space so that it can be detected and measured. Matter occurs in three states (i) Solid (ii) liquid (iii) Gases. Energy : It is the capacity to do work. Every physical and physiological activity requires energy hence energy is essential for life. Note : Matter and energy are closely related to each other. And universe is a “matter-energy complex”. Forms of energy : (a) Potential energy or stored energy : The energy which is present in the chemical bonds of the substance or due to the position of the object is called potential energy. (b) Kinetic energy : Energy due to the motion of the object is called kinetic energy. FORMS OF KINETIC ENERGY (i) Energy of heat (ii) Radiant energy (iii) Mechanical energy (iv) Electrical energy (v) Sound or sonorous energy (vi) Atomic or nuclear energy COMPOSITION OF MATTER Matter is any substance that possesses mass and occupied space. Physical organization of matter : Three grading levels occurs in the organization of matter. (i) Sub atomic level : At this level matter contains three fundamental particulate units known as electrons, protons, neutrons. (ii) Atomic level : Proton’s, neutrons and electron associated in increasing numbers and form second level unit of matter known as “Atom”. Atom is smallest unit of matter that participates in chemical reaction without dissociation. So atom known as the primary reactive unit of the matter. (iii) Molecular level : Association of two or more atoms form molecules which is of two types. (a) elements – Made up of same type of atoms. e.g., O2, H2, N2 etc. (b) Compounds – Made up of two or more than two types of atoms. e.g., H2O, CH4 etc. Atomic Number – Number of protons present in the nucleus is called Atomic number. Mass Number – Total number of proton’s and neutrons is called mass number. Isotopes – Atoms of a given element which have same atomic number (Nuclear charge) but different mass number are called isotopes. Radio Isotopes : The isotopes which are formed by (atomic decay) or, emission of particles (α, β, γ) Isobars : Isobars are the atoms of different elements with the same mass number but different atomic number are called Isobars. Mixture : It is the group of two or more substances which are intermixed together. Mixture are of three types : (a) Solution (b) Colloids (c) Suspensions (A) Solution : Homogenous mixture of two or more substances. It has two components. (i) Solvent : The substance which is present in large amount e.g., water, alcohol etc. (ii) Solute : Substances present is smaller amount e.g., Glucose, Salts, etc. Concentration of solutions : Concentration of solution expressing in following terms. (i) Molarity : Molarity of a solution is the number of moles of the solute per litre of solution. (ii) Mole : It is the unit of quantity of the substance. A collection of 6.02 × 1023 particles is called mole. This number (6.02 × 1023) is called Avogadro’s number. (B) Colloids : Colloids are heterogeneous mixture is which size of the solute particles is more than the true solutions. e.g., Milk, Gum, Gelatin etc. (C) Suspension : Suspensions are heterogeneous mixture that have visible solute particles which are often settle down at the bottom of the beaker. e.g., mixture of water and soil.

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Chemistry comes alive-2 CHEMICAL BONDS The forces of attraction which combine atoms to each other are called chemical bonds. Types of chemical bonds : Chemical bonds enable an atom to obtain a stable electronic configuration. This is done by gaining, losing, and sharing of the electrons from other atoms. So, on the basis of gaining, losing or sharing of electrons bonds are of following types. (1) Electrovalent or ionic bond : The bonds which are formed by the transfer of electron is called electrovalent or ionic bond. The atom which lose electron is called cation (+ve ion) the atom which gain electron is called anion (–ve ion) e.g., formation of NaCl by positively charged Na+ion and Negatively charged Cl¯ is the example of ionic bond. (2) Covalent bond : The bond which is formed by the sharing of electron is called covalent bond. Formation of O2 molecules by two oxygen atom is the example of covalent bond. (3) Hydrogen bonds : Hydrogen bond is the bond which is formed between hydrogen to an electronegative atom (F, O, N). It is a very weak bond and having more importance in biological world. CHEMICAL REACTIONS Formation or breaking of chemical bonds leads to the association or dissociation of the element.It is called chemical reaction. In chemical reaction energy is either released or absorbed due to the breaking or formation of bonds. Chemical reaction : Representation of chemical reaction in the form of equation by the proper symbols of reactant and product is called chemical reaction. e.g., C6H12O6 + 6O2 → 6CO2 + 6H2O + energy. Types of chemical reactions : Chemical reactions of three types: (A) Synthetic (B) Decomposing (C) exchange reactions. (A) Synthetic reactions : Formation of complex molecules by simpler molecules. 6CO2 + 12H2O ⎯⎯ C6 H12 O 6 → glucose (B) Decomposing reaction : Breakdown of complex molecules in to simpler molecules. C6 H12 O6 + 6O 2 ⎯⎯ 6 CO 2 + 6H 2 O → glucose (C) Exchange reactions : In this type of reaction both formation and breakdown of bonds taking place. NaOH + HCl ⎯⎯ → NaCl + H2O (castic soda) Hydorgen chloride Sodium chloride water REVERSIBILITY OF CHEMICAL REACTONS OR CHEMICAL EQUILIBRIUM A reaction which can go in both forward and backward direction is called reversible reaction it is represented by this sign. When chemical reaction takes place in both direction with the same rate is called chemical equilibrium. ATP ADP + ip (Adinosine triphosphate) (Adinosine diphosphate) inorganic phosphate FACTORS AFFECTING RATE OF CHEMICAL REACTION (A) Medium of the chemical reactions rate of reaction increasing in this manner of medium. Solids ⎯⎯ Liquids ⎯⎯ Gases. → → (B) Temperature : Temperature increases rate of reaction up to optimum level, temperature decreases rate of reaction due to decreasing kinetic energy of reactant molecules. (C) Concentration : More Concentration of the substrate = Rate of reaction higher. Less concentration of the substrate = Rate of reaction lower. (D) Catalyst : Increases the rate of reaction by the lowering down the activation energy of the reactants. COMPOSITION AND REACTONS OF LIVING MATTER Living matter is made up of six main components which are divided in to two types. (A) Organic – Carbohydrates, Proteins, Lipids, Nucleic acids. (B) Inorganic – Water and Minerals. WATER Occurrence. Water is the most abundant substance, covering 70% of earth’s surface in the form of oceans, with many more areas being covered by ice sheets and fresh water reservoirs. It constitutes 70–90% of living cells, (i) Dipole. Water is a small polar molecule having positive and negative charges. Oxygen atom comes to have a slightly negative charge (2 δ¯) due to coming of electrons of Hydrogen atoms nearer to it. Hydrogen atoms, on the other hand, develop a slightly positive charge (δ+). There is thus an uneven charge distribution over the molecule. The phenomenon is called polarity. Water molecules behave as a - 10 -

Chemistry comes alive-2

dipole with oxygen atom functioning as negatively charged region whil
								
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