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Constructing Ideas in Physical Science

CIPS Institute for Middle School Science Teachers. Constructing Ideas in Physical Science. Joan Abdallah , AAAS Darcy Hampton, DCPS Davina Pruitt-Mentle , University of Maryland. Session 8 Debriefing. What do you remember from yesterday’s session (no peeking at text or notes)

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Constructing Ideas in Physical Science

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  1. CIPS Institute for Middle School Science Teachers Constructing Ideas in Physical Science Joan Abdallah, AAAS Darcy Hampton, DCPS Davina Pruitt-Mentle, University of Maryland

  2. Session 8 Debriefing • What do you remember from yesterday’s session (no peeking at text or notes) • What were the “essential questions” being asked/explored • What conclusions did “we” decide 8/2-8/13

  3. Deeper Questions • What deeper questions could you envision students asking? • What misconceptions or misinterpretations can you foresee? • How or what would you say? 8/2-8/13

  4. Deeper Questions or Possible Misinterpretations “What makes light”? “What makes energy”? “What makes different colors”? What would you say? 8/2-8/13

  5. Electromagnetic Spectrum How Roy G. BV Lost a Vowel This was originally "ROY G. BIV", because it used to be common to call the region between blue and violet "indigo". In modern usage, indigo is not usually distinguished as a separate color in the visible spectrum; thus Roy no longer has any vowels in his last name. 8/2-8/13

  6. Radiant Energy See Handout: Continuous and Line Spectra Read Aloud 8/2-8/13

  7. So…. • Things are made up of atoms • Atoms • Protons • Electrons • Electrons do a lot of spinning and hopping around (that’s what causes things to have certain shapes and textures) • When electrons get excited, they jump from lower ground state to excited state and then back to rest again • This jumping back and forth = radiant energy 8/2-8/13

  8. How Do you Measure Radiant Energy? • In order to understand behavior of e-, you need to know their: • Velocity • Location • Werner Heisenberg (highs-en-berg), German, showed that it is impossible to know both the exact position and the exact momentum of an object (e-) at the same time (Heisenberg’s Uncertainity Principle) • Can not measure where the e- is since the “nature” of measuring is to “move” something • To know location you would have to “measure” it –but when you measure it would effect (change) the velocity • Smaller something is the more uncertain the position will be after measuring it • (Δx) (Δmv)  h/4 • (Δx) = change in position • (Δmv) = momentum = mass x velocity (related to KE) • h/4 = some constant (Planck’s constant/4) Need more coffee? 8/2-8/13

  9. 1923, de Broglie (French) Used Planck’s/(and Einstein) idea…that radiation is made up of packets of energy (this gave waves properties of particles) He wanted to prove that particles could have properties like waves This enabled de Broglie to predict the wavelength of a particle when given mass (m) and velocity. General Trend as mass (e-) increases,  decreases e- mass ↑  ↓ The de Broglie Hypothesis 8/2-8/13

  10. The de Broglie Hypothesis cont. • Using E = mc2 (Einstein) and E = h  (Planck) • Derived: mc2 = h  • Substituted v (general velocity) for c • Substituted v/  for , because the frequency of a wave is equal to its velocity/by its wavelength • mv2 = h/ • or  = h /mv2 = h/mv See: http://cougar.slvhs.slv.k12.ca.us/~pboomer/chemtextbook/cch9.html 8/2-8/13

  11. The de Broglie Hypothesis cont. • From this, shown that e- stream acts in the same way as a ray of light • Given credit for indicating how to predict the wavelength of particular electrons • Also showed that e- have properties of both waves and particles = wave-particle duality of nature • This is why you can not measure the velocity & location of e- at the same time 8/2-8/13

  12. Two Formulas • (m) X (s-1) = c (where c =speed of light or 3.00 x 108 m/s) • Louis de Broglie suggested that the e- in its circular path about the nucleus has associated with it particular wavelengths, and also that the wavelength of the e- depends on its mass and velocity • He called this matter waves, and used it to describe the wave characteristics of material particles •  = h/mv • mv also called momentum • h= Planck’s constant 6.63 x 10-34 J.s (1 J = 1 kg m2/s2) Show Subscripts and Symbols See handout (5.2) 8/2-8/13

  13. De Broglie = e- act as waves (properties of  and ) Schrodinger = e- act as particles -- different  (energy property) &  (mass) The link between these two concepts = h = Planck’s constant Wave-particle duality of nature Making the Connection 8/2-8/13

  14. Shows or proves that a beam of e- will produce a diffraction pattern like light patterns Bohr and Schodinger called this : wave or quantum mechanics i.e., where are we more likely to “find” e- at a given moment in time 1s _ 2s_ 2p _ _ _ 1 & 2 = shells S,p,d,f = subshells _ = orbitals Distance between the rings = “nodes”, places where you will not find e- Wave-particle Duality of Nature 8/2-8/13

  15. Summary • Planck’s hypothesis stated that energy is given off on quanta (photon) continuously • Bohr showed that absorption of light at set  correspond to definite changes in energy of the e- • Reasoned that orbits (rings) around nucleus must have a definite diameter and that e- could occupy only certain orbits 8/2-8/13

  16. Summary cont. • The energy absorbed when the atom was excited = the energy difference between orbits • Because these orbits represent definite energy levels, a definite amount of energy is radiated • The size of the smallest orbit an e- can occupy (one closest to nucleus), the ground state, can be calculated • Energy is determined by the movement of e- between energy levels that are specific for each element • The same set of energy levels will always produce the same spectrum 8/2-8/13

  17. To Learn More • CEA Light Tour [Local] See Handout From: http://cse.ssl.berkeley.edu/light/light_tour.html 8/2-8/13

  18. Other Resources • Waves –Virtual Lab [Local] • Exploring Earth [Local] Observe the change in a star's spectrum as its motion changes • Electromagnetic spectrum - Wikipedia • Discovery-The Color Spectrum How does it work? [Local] 8/2-8/13

  19. But I can not see e-, so how do we know? 8/2-8/13

  20. States of Matter • Matter- has mass, occupies space • Physical states of matter • Solid • Liquid • Gas • Plasma One of the four states of matter. (The other three are solid, liquid and gas.) Consists of a gas of positively charged and negatively charged particles with approximately equal concentrations of both so that the total gas is approximately charge neutral. A plasma can be produced from a gas if enough energy is added to cause the electrically neutral atoms of the gas to split into positively and negatively charged atoms and electrons. See also: The Plasma State of Matter. www.spacescience.org/ExploringSpace/Glossary/1.html 8/2-8/13

  21. Kinetic Molecular Theory of Matter • States: • All matter is in constant motion • An increase in temperature increases motion and decreases attraction forces holding the matter together • S  L  G  P 8/2-8/13

  22. Physical Properties Can be observed without changing form Color Odor Taste Size BPo MPo Density Specific heat (Cp) Hardness Solubility Mass Temperature Heat capacity Chemical Properties Undergoes changes in chemical composition Flammability or not flammable Reacts/failure to react with another Decomposes Rusting Combustion Physical vs. Chemical Properties 8/2-8/13

  23. Intensive Values do not depend on size of portion Temperature MPo BPo FPo Extensive Depend on sample size Mass Volume Length Properties can also be classified as: 8/2-8/13

  24. Properties • Molecules vibrate faster when they are stirred-therefore, this helps them dissolve faster • When heated dissolves faster • At certain temperature (w/ a solid) when heat added, the heat breaks the bonds. Solid matter changes to liquid (Melting Point MPo) • With a solid when freezes, attractive forces cause molecules to lock together into solid state (Freezing Point FPo) 8/2-8/13

  25. Liquid Changes • Change of liquid into vapor  evaporation • Change of vapor into a liquid  condensation • Opposite of condensation  evaporation • Opposite of evaporation  condensation 8/2-8/13

  26. Changes cont. • As temperature falls, and the gaseous molecules slow down, their weak attractive forces get an opportunity to bind the molecules together and change the gas (vapor) into a liquid. When water vapor touches cool dust particles in the air, condensation takes place. The droplets of water, suspended in the air, form clouds and rain • Gas  Condensation  Liquid • The changing of a solid into a gas without becoming liquid  sublimation. A lot of heat is added to the solid. This added heat causes the molecular vibrations to become so violent that the molecules of the solid completely break away from each other and enter into a gaseous state • Solid  Sublimation  Gas • Ex. Mothballs, vaporization (nuclear fallout) 8/2-8/13

  27. Changes cont. • We know that water vapor will condense on a cool speck of dust. If the water vapor touches a very cold speck of dust in the air, the gaseous water may crystallize without condensing first. The ice crystals, suspended in the air, form clouds. If conditions are right, these crystals may fall to the ground as snow. • The changing of a gas into a solid = sublimation • By definition, sublimation can indicate going from gas to solid or from solid to gas…although in “chemistry” usually implies going from the solid state to a gas state. 8/2-8/13

  28. Putting It All Together GAS Evaporation Sublimation Deposition Condensation SOLID LIQUID Melts Freezes 8/2-8/13

  29. Physical Change No new substance is ever formed Tearing paper Sulfur & iron Sharpening Bite Chew Breaking glass Chemical Change Involves a change in basic nature (chemical composition) Change in at least one new substance Sulfur & iron heated Burning paper Digesting Sour milk Detonation Property Changes 8/2-8/13

  30. Rust Melts Sharpening Digesting Biting Burning Slicing Detonation Souring Breaking C P P C P C P C C P Quiz 8/2-8/13

  31. Break? 8/2-8/13

  32. CIPS • Unit 4 • Cycle 1 • Activity 1,2 & 3 8/2-8/13

  33. Physical and chemical changes are always accomplished by energy transfer The most common form of energy transform or change is heat Heat is a form of energy that flows between a system and its surroundings Heat flows from a warmer object to a cooler one Ex. Object A = 25°C Object B = 20°C What happens when they are mixed? Energy will continue to transfer until the temperature of the objects are equal. The energy transfer as a result of a temperature difference is calledheat and is represented by the letter (q). Energy & Heat 8/2-8/13

  34. Energy (continued) • If energy is absorbed = endothermic reaction • If energy is given off = exothermic reaction • Match = exothermic • Cold pack = endothermic • Both forms require a certain amount of energy to get started – activation energy • Quantitative measurements of energy changes are expressed in joules (J). This is a derived SI unit • Older unit = calorie • One calorie (c) = 4.184 J • (C) dietary unit  calorie (c) • The heat needed to raise 1 g of a substance by 1°C is called specific heat (Cp) of the substance Examples: Sand and water – different Cp values Which gets hotter at the beach? Which cools down faster? 8/2-8/13

  35. Dietary Calories • The heat required to increase the temperature of 1g of water 1°C = 4.184J • Dietary Calories (C) are 1000 times as large as a calorie (c) • Caloric values are the amount of energy the human body can obtain by chemically breaking down food • The Law of Conservation of Energy shows that in an insulated system, any heat loss by 1 quantity of matter must be gained by another. The transfer of energy takes place between 2 quantities of matter that are at different temperatures until they both reach an equal temperature Example: An average size backed potato (200g) has an energy value of 686,000 J. How many calories is this? 4.184J = 1 c, 1000 c = 1 C 686000J/4.184 J = 164,000 c 164,000 c/ 1000 C=164C 8/2-8/13

  36. Energy Transfer • The amount of heat energy transferred can be calculated by: • (heat gained) = (mass in grams)(change in T)(specific heat) • q = (m)(T)(Cp) • T = Tf - Ti Example: How much heat is lost when a solid aluminum block with a mass of 4100g cools from 660.0°C to 25°C? (Cp = 0.902 J/g°C) q = (m)(T)(Cp) T = 660.0°C - 25°C = 635°C therefore: q = (4110g)(635°C)(0.902 J/g. °C) = 2,350,000 J 8/2-8/13

  37. Mixture Most Natural Samples Physical combination of 2 or more substances Variable composition Properties vary as composition varies Can separate by physical means Pure Substance Few naturally pure gold & diamond Only 1 substance Definite and constant composition Properties under a given set of conditions Matter 8/2-8/13

  38. Heterogeneous Visible difference in parts and phases Oil and vinegar Cookie Pizza Dirt Marble Raw Milk Homogeneous Only 1 visible phase Homogenized milk Air (pure) Metal Alloy (14K gold) Sugar and Water Gasoline Mixture 8/2-8/13

  39. Compound aspirin, H2O, CO2 Can be broken down into 2 or more simpler substances by chemical means Over six million known chemical combinations of 2 or more elements 7000 more discovered per week with chemical abstracts service Definite-constant element composition Element Au, Ag, Cu, H+ Pure and cannot be divided into simpler substances by physical or chemical means 90 naturally occurring 22 synthetic Pure Substance Element Simpler Compound Compound Element Element 8/2-8/13

  40. Heterogeneous materials Homogeneous materials Solutions Pure substances Mixtures Compounds Elements Matter

  41. CIPS Unit 5 8/2-8/13

  42. Proton: (+) 1.673 x 10-28 g Discovered by Goldstein (1886) Inside the nucleus (credit given to Rutherford – beam of alpha particles on thin metal foil experiment. Explained nucleus in core, made up of neutrons and protons) Neutron: (no charge) 1.675 x 10-24 g Discovered by James Chadwick (1932) Inside nucleus Electron: (-) Outside ‘e’ cloud 9.109 x 10-28 g (1/1839 of a proton) Discovered by Joseph John Thomson (1897) It’s charge to mass ration (e/m) = 1.758819 x 108 c/g c = charge of electron in Coulombs Millikan determined mass itself Subatomic ParticlesBuilding Blocks of Atoms 8/2-8/13

  43. Atoms • Atom – smallest particle of an element that can exist and still hold properties • “Atomos” – Greek – uncut/indivisible. Democritus proposed that elements are composed of tiny particles • John Dalton (1808) published The Atomic Theory of Matter • All matter is made of atoms • All atoms of a given type are similar to one another and different from all other types • The relative number and arrangement of different types of atoms contained in a pure substance determines its identity (Law of Multiple Proportions) • Chemical change = a union, separation , or rearrangement of atoms to give a new substance • Only whole atoms can participate in or result from any chemical change, since atoms are considered indestructible during such changes (Law of Conservation of Mass) • Antonine Lavoier demonstrated via careful measurements that when combustion is carried out in a closed container – the mass of the products = the mass of the reactants 8/2-8/13

  44. H = 1 O = 16 H2O 2 x 1 = 2 1 x 16 = 16 Total = 18  Billy = 150 Susie = 100 Billy4Susie = 800 Formula Mass H2SO4 H = 2x1 = 2 S = 1 x 32 = 32 O = 4 x 16 = 64 Total 98 2CaCl2 Ca = 2x40 = 80 S = 4 x 36 = 144 Total 224 8/2-8/13

  45. Universe H 75-91% He 9% Earth O2 49.3% Fe 16.5% Si 14.5% Mg 14.2% Atmosphere N2 78.3% O2 21% Human Body H2 63% O2 25.5% C 9.5% N2 1.4% Abundance of Elements in Matter Earth’s Crust • O2 60% • Si 20% • Al 6% • H2 3% • Ca 2.5% • Mg 2.4% • Fe 2.2% • Na 2.1% 8/2-8/13

  46. Geographical Names Germanium (German) Francium (France) Polonium (Poland) Planets Mercury Uranium Neptunium Plutonium Gods He (helios – sun’s corona) Properties (color) Chlorine - chloros – greenish/yellow Iridium –iris – various colors Element Names – based on 8/2-8/13

  47. Chemical Symbols • 1814 – Swedish – Jons Jakob Berzelius • Symbols = shorthand for name • N = nitrogen • Ca = Calcium • Latin or other name • Latin Iron Fe Ferrum Gold Au Aurum Antimony Sb Stibium Copper Cu Cuprum Lead Pb Plumbrum Mercury Hg Hydrargyrum Potassium K Kalium Silver Ag Argentum Sodium Na Natrium Tin Sn Stannum • German Tungsten W Wolfram 8/2-8/13

  48. Generic Nomenclature: Provisional Names • International Union of Pure and Applied Chemistry (IUPAC) • Latin – Greek Names • 0 =nil, 1=un, 2=bi, 3=tri, 4=quad, 5=pent, 6=hex, 7=sept, 8=oct, 9=enn • + ium • i.e. • 104 un nil quad ium Unq • 105 un nil pentium Unp • 106 un nil hex ium Unh • 110 un un nil ium Uun • Most nave been given names anyway 8/2-8/13

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