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UVM CHEM 023 - Matter and energy - outline

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10Chapter 2: Key ConceptsMatter and energy - outline• Length scales: macroscopic, microscopic andparticulate matter• Using models to describe/visualize materials• Types/classification of matter– States of matter: solid, liquid, gas.– Elements and compounds– Pure substances and mixtures• The electrostatic nature of matter• Chemical and physical changes– The characteristics of a chemical changeMatter and energy - length scales• Length scales: macroscopic, microscopic andparticulate matter• Using models to describe/visualize materials• Types/classification of matter– States of matter: solid, liquid, gas.– Elements and compounds– Pure substances and mixtures• The electrostatic nature of matter• Chemical and physical changes– The characteristics of a chemical change11Length scales• Matter: Anything that has mass (sometimesexpressed as weight) and takes up space. Stuff.• Not:– Electricity– Light or heat– X-rays, microwaves or radio waves• Matter can be observed and/or thought about atdifferent levels:– Macroscopic– Microscopic– ParticulateLength scalesChemistryPhysical properties12Influenza virus100 nmThings NaturalThings ManmadeMatter and energy - models• Length scales: macroscopic, microscopic andparticulate matter• Using models to describe/visualize materials• Types/classification of matter– States of matter: solid, liquid, gas.– Elements and compounds– Pure substances and mixtures• The electrostatic nature of matter• Chemical and physical changes– The characteristics of a chemical change13Models of matter• Chemists “imagine” the nature of the behavior of the tinyparticles that make up matter, and they use thatknowledge to carry out changes from one type of macro-or microscopic matter to anotherThis part of the particleloves waterThis part of the particlehates water• In water, these particles associate to make rods and spheresMinimal models and symbolsvanillinchemical formulaball-and-stick modelspace-filling modelLewis structureOHOOCH314Models of matter• These models were only “ideas” until very recently– Too small to see with microscopes– Likely structures inferred from their properties, and thearrangement of atoms• Then in 2009…Scientists at IBM in Germanyused a “force microscope” tosee this image of pentaceneSo our ideas about theshapes of moleculeswere pretty goodThinking like a chemist“How does what I knowabout the particlesexplain what I see inthe beaker?”15Matter and energy - types of matter• Length scales, macroscopic, microscopic andparticulate matter• Using models to describe/visualize materials• Types/classification of matter– States of matter: solid, liquid, gas– Elements and compounds– Pure substances and mixtures• The electrostatic nature of matter• Chemical and physical changes– The characteristics of a chemical changeStates of Matter• Gas– The air you breathe– Particles are independent of one another, moving randomlywith empty space between them• Liquid– The water you drink– Particles move freely among themselves, but there is noempty space between them• Solid– The food you eat– Particles vibrate in fixed positions relative to one anotherand there is no empty space between them16Matter and energy - types of matter• Length scales, macroscopic, microscopic andparticulate matter• Using models to describe/visualize materials• Types/classification of matter– States of matter: solid, liquid, gas– Elements and compounds– Pure substances and mixtures• The electrostatic nature of matter• Chemical and physical changes– The characteristics of a chemical change17ElementsParticulate and macroscopic viewsof elements(materials containing just one sort of atom)18Particulate and macroscopicviews of elements(materials containing just one sort of atom)Silver and a particulate-level modelof silver atoms19Familiar objects that are nearly pureelementsWhat are you worth, as elements?About $1 (and your skin, as hide, isworth around $3.50)20Alchemy - changing lead into gold?• This is not actuallypossible• You cannot, usually,change one elementinto another• Exception = nuclearchemistryDetail of Alchemist in His Workshop by David Teniersthe Younger (1610–1690). Eddleman Collection, CHFSide track - Alchemy• In the middle ages people didn’tdistinguish between scientific and“spiritual” ideas• Alchemists believed that their ownspiritual state (purity, lack of doubt)affected the outcome of their experiments• Many people see medieval alchemy asthe birth of chemistry• Many of the processes early alchemistsused are familiar to chemists today• They understood that some substancescould not be separated into other stablepure substances (elements)GoldDistillationPhosphorousHeat(we still use this one!)21Compounds(materials containing more than one type of atom)• An infinite number of compounds can be made bycombining the atoms of different elements in differentways• The resulting materials are often far more valuable!• Pure gold = $30/gram• Compound containing gold– Auranofin = $113 for 90mg($1,250/gram!)– And more than 60% of themolecule by weight isn’t goldOAuOAcOAcAcOAcOPChemical formula• A combination of the symbols of all the types ofatoms (elements) in the substance showing therelative amounts of eachH2O Water CO2 Carbon dioxide CH4 Methane C6H12O6 Glucose HCl Table salt N2 Nitrogen SiO2 Silicon dioxide O2 C9H8O4 Asprin22Particulate and macroscopicviews of compoundsSalt crystal“Familiar” compounds(Products that contain only one substance)NaHCO3NaAl(OH)2CO3 + flavorNaOH(NH4)2S2O3+ H2OC10H14N2 + many more!!23MatterGas Liquid SolidPure materialone substance onlyMixture (impure)two or more substancesElementonly one typeof atomCompoundmore than onetype of atomMatter and energy - types of matter• Length scales, macroscopic, microscopic andparticulate matter• Using models to describe/visualize materials• Types/classification of matter– States of matter: solid, liquid, gas– Elements and compounds– Pure substances and mixtures• The electrostatic nature of matter• Chemical and physical changes– The characteristics of a chemical change24Pure substances and mixtures• A pure substance contains just one type of molecule,one sort of substance or chemical• It cannot be separated into parts by a physicalchange• (example: changing pure water into oxygen andhydrogen requires a chemical change, the


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