The Atom in Modern Chemistry Chemists study Scanning Tunneling Microscope image of Si atoms Properties of substances and their transformations into http www youtube com watch v HXIDJother substances NFtr4 feature related How and why chemical reactions occur Creation of new substances and tailoring properties of existing ones Fig 1 CO p 3 Definition Chemistry in the 30 s Chemistry is the study of the nature properties and composition of matter and how these undergo changes Chemistry of Happiness Physical Biological Sciences Physical Inorganic and Organic Chemistry Today Chemistry overlaps with many other traditional fields Geology geochemistry Biology biochemistry Astronomy astrochemistry Neurology neurochemistry Chemistry in Science Technology and Society Solid state physics Molecular biology Synthetic methods Analytical methods Environmental studies Food Chemistry Microelectronics Medicine Pharma Energy Green Nanotechnology Consumer Products Chemistry forms the indispensable foundation of disciplines such as biology medicine and materials sciences Fig 1 CO p 3 Chemicals Everywhere 3 trillion global enterprise Polymers the largest revenue segment at about 33 percent of the basic chemicals dollar value Life sciences 30 percent of the dollar output of the chemistry business 2007 http en wikipedia org wiki Chemical industry The Alchemists Chemistry established in 18th century Over a millennium before came the Alchemists Transformation lead into gold through extraction of properties color ductility etc from base materials to gold Fig 1 1 p 4 Modern Chemistry The Sceptical Chymist Robert Boyle 1660 Chemistry should cease to be subservient to medicine or to alchemy and rise to the status of a science advocated a rigorous approach to scientific experiment theories must be proved experimentally before being regarded as true In the late 8th century Jabir ibn Hayyan known as Geber in Europe introduced a new approach to alchemy based on scientific methodology and controlled experimentation in the laboratory The scientific method Hypothesis Rigorous testing with experiments and analysis Elevated to scientific law after many rounds of testing Becomes predictive in alternative environments Laws are a summary of observations Chemical Laws Avogadro s Law Law of Conservation of Mass Law of Conservation of Energy Law of Definite Proportions Law of Multiple Proportions Conservation of Mass and Energy Total amount of matter in a chemical reaction is conserved Matter is neither created or destroyed Total amount of energy in a chemical reaction is conserved Chemical energy in reactant and product differ but sum of it with thermal electrical mechanical energy is conserved Exception nuclear E mc2 where sum of mass and energy is conserved Macroscopic and Nanoscopic Models in Chemistry Macroscopic m mm flasks beakers balances centrifuges etc Nanometer 1nm 10 9 m billionth meter Macroscopic and Nanoscopic views of an experiment electrolysis of water Fig 1 2 p 6 Classification of Substances and Mixtures Chemists could classify Based on simple physical tests like dissolving in solvents and finally chemical tests like thermal decomposition or other reactions Fig 1 3 p 7 Heterogeneous wood milk granite blood etc Cu NO3 6H20 CdS Add H2O and dissolve the nitrate CdS is insoluble Filter off CdS leaves nitrate solution Dry and separate two substances Fig 1 4a p 7 Homogenous Uniform properties throughout Saline solution Air Homogenous materials may be mixtures of substances Freezing boiling using solvents to separate them Example salt water evaporation separates salt from water Pure substances table salt no NaCl yes impurities exist in table salt like iodine Silicon purification to the highest level enabled microelectronic devices ELEMENTS fundamental building block of matter cannot be decomposed into two simpler substances Substance with two or more elements is a compound Zone refining a 10 inch long silicon boule purity less than a ppm Fig 1 5 p 8 Compounds Binary two element compound water ammonia octane carbon dioxide Ternary three elements CuSO4 Quaternary four elements Latin origin binarius meant two by two 2 binary 3 ternary 4 quaternary 5 quinary 6 senary 7 septenary 8 octal 9 nonary 10 decimal 11 undenary 12 duodecimal 16 hexadecimal 20 vigesimal 60 sexagesimal Fig 1 6 p 10 ELEMENTS 118 Gold lead copper sulfur 2nd Millenium BC Iron extracted from oxide Metallurgy Iron age Latin names Au aurum Cu cuprum Fe ferrum Hydrogen water former hydro Hg 4th century B C Aristotle refers to mercury as hydro argyros which translates as water silver or liquid silver The Romans modified mercury as Hydragyrum from which we get mercury s chemical symbol Hg Europium Germanium Holmium stockholm Uranium Uranus Ce Cesium blue sky latin caesius Cm Curium Madame Curie Sg Seabourgium Glenn Seabourg UCLA Indirect evidence for the existence of atoms laws of chemical combination Democritus 460 370 BC postulates matter is composed of atoms as fundamental building blocks in matter whose motion is random in vacuum Matter is indivisible at the limit of the atom Lacked experimental methods to test these postulates they remained assertions Laws of of chemical combination When substances react they do so by following certain laws These laws are called the laws of chemical combination These formed the basis of Dalton s atomic theory of matter Law of conservation of mass Phlogiston driven out of wood as it burns to form ash metal oxidized to Calx The chemical balance Antoine Lavoisier carefully weighed the reactants and products in a chemical reaction Although matter can change its state in a chemical reaction the total mass of matter is the same at the end as at the beginning of every chemical change Matter is neither created or destroyed in a chemical reaction it is conserved Lavoisier During any physical or chemical change the total mass of the products remains equal to the total mass of the reactants Law of conservation is also known as Law of indestructibility of matter law of conservation of mass 10 grams of CaCO3 on heating gave 4 4g of CO2 and 5 6g of CaO Show that these observations are in agreement with the law of conservation Solution Mass of the reactants 10g Mass of the products 4 6 5 6g 10g Since the mass of the reactants is equal to the mass of the products the observations are in agreement with the law of conservation of mass Law of definite proportions 1794 Joseph Proust In a given chemical compound the proportions by mass
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